97 GTX - Am I too Lean? - High RPM Power Loss - At Lake

[digital sol]

I made it down to the lake with my 97 gtx, 787 powered ski however I am having an issue and wanted to check with the experts. The ski fires right up & idles around 1300-1400 rpm "Ill find the adjuster for this and adjust to 1500, I cant see it with the carbs installed and forget off hand which car its on". There was a little smoke inside the sea doo engine area/exhaust area but after a few seconds it went away and during my testing with the seats off the entire time I never saw any more smoke or water inside the hull.

I also confirmed the water pump is working because the exhaust was still warm to the touch after riding.

Low rpms and partial throttle seems ok but when I mash the throttle it takes off hard for 1-2 seconds then falls flat on its face. I did a plug chop by mashing the throttle and then killing the engine and immediately pulling the plugs. They are brownish but seemed really clean. I had "1" low rpm hesitation as well but I set these carbs to factory spec.

Things I did
-carbs freshly rebuilt w/oem kit from OSD parts
-selector valve replaced
-lines are replaced/not grey
-br8es plugs

It was a restoration ski but wanted to mention those parts are new. Should I adjust the high adjusters out slightly? Should the plugs be wet or clean on a plug chop?

I am running premix 40/1 and the only other thing I noticed is the oil line that goes from the top of the oil tank w/the breather valve to the engine has an air pocket in it towards the top of the hose but the bottom of the hose nearest the engine does have oil in it.

Sorry if my pics suck, it was hard to pull plugs on the lake w/out a seat & boats flying by lol! I am hoping to tweak the carbs without removing them. I was thinking of making low and high a little more rich and retesting but wanted to check with the experts first.





This is the proper color for plugs right? The motor hasnt ran in nearly 12 months so I might take it out and just be easy on her a little longer then retest.

 

[digital sol]

One thing I just thought of..can I just pull the choke while going WOT and if the hesitation stops @ high rpm's assume I am running lean & need to adjust the high carb screws? Thanks for the info fellas!!

Edit: As far as mods go, it does have a worx intake grate and solas impeller

 

[digital sol]

I took it out again for a short cruise and had issues with stumbling and getting over 5k but when I pulled he seat I had oil around the plugs on the valve cover. They were not torqued down enough after removing them earlier to snap the pics. I won't be able to retest with property torqued down plugs until tomorrow but I'm assuming the original issue is still there.

 

[soccerdad]

Yes you can pull the choke and see if it picks up. If so, you are lean. But really, if your carbs are correct, you should not need to open the HS screws. I have the PTO HS screw open about 1/8 but that is it. That plug is too hard to read. But it sounds like air is sucking in your fuel system. Maybe check your water separator bowl or your selector switch. Or ride with the seat off WFO, and look for air bubbles while trying not to crash!:auto:

 

[digital sol]

Soccerdad thank you so much for your help. I'll try it out tomorrow and also get better pictures. I am pretty certain mine is at 0 but I'll double check tomorrow.

As for riding with the seat off so you mean bubbles in the fuel lines? My lines are black not clear unfortunately but I do have an inline fuel filter right near the carbs I can look at. I will tighten up all the clamps on my fuel lines as well. The fuel selector didn't look bad but I replaced it anyways last week with an oem replacement.

When it did hook and rip it felt great. Tach bounced to high 6 low 7k rpms and it felt way quicker than last year. Just gotta figure out this hiccup

 

[digital sol]

Took it for a test run and had the same issues. Sometimes while turning I might spin 6k+ rpms for a split second but normal driving and hitting throttle it wants to take off then stumbles and bogs down. I am limited to about 5k rpms

If i pull choke while WOT it falls on its face immediately so I dont think its lean. I backed the PTO HS out to 1/8th and had the same results. The manual calls for 1/2 on the pto and it still ran like crap at 1/8th but I will close it and retest again. Cant hurt at this point.

I sprayed that fogger stuff around the carbs and such and it didnt increase or decrease the rpms etc so it seems its all sealed up. Kind of bummed at this point and dont really wanna spend all vacation working on it. I might just drop it off somewhere but no telling on a holiday week if they will even get to it anytime soon. I also considered buying rebuild carbs but at $400 id rather not. I already have 600+ into it since the resto

 

[Mekanix]

Did you use any of the springs that were in the kit ?

This sounds exactly like fuel delivery is weak.
As in your getting air in the fuel lines from: fuel selector, water separator, any line connection, tank tending unit... or the fuel pump itself. I've actually damaged/ stretched two fuel pump diaphrams while doing pop off tests on my own machines.

Once you get to 4500 and your just light on the throttle, The raves are still down and the main jet is slowly coming in. This is where you are reaching the max of the pilot circuit. At about 5000-5200 your using 100% of the pilot circuit and 20% of the main but everything after that has to do with how well the main circuit is working.

You can actually see it on the tach when the transition happens when playing between 4500 and 5500 rpm.

Yours works but then dies.
As in the main works and then sucks all the fuel out of the chamber faster than it can refill.


So check for air leaks to start.

Another way to help see if it's air or not is to use clear vinyl line from the tank to the carb directly and same for the return.

Then look for air bubbles while riding. Make a longer loop so that you can see the fuel move.
I just made it long enough that I could zip tie it to the seat hook for both lines.

 

[digital sol]

Did you use any of the springs that were in the kit ?

This sounds exactly like fuel delivery is weak.
As in your getting air in the fuel lines from: fuel selector, water separator, any line connection, tank tending unit... or the fuel pump itself. I've actually damaged/ stretched two fuel pump diaphrams while doing pop off tests on my own machines.

Once you get to 4500 and your just light on the throttle, The raves are still down and the main jet is slowly coming in. This is where you are reaching the max of the pilot circuit. At about 5000-5200 your using 100% of the pilot circuit and 20% of the main but everything after that has to do with how well the main circuit is working.

You can actually see it on the tach when the transition happens when playing between 4500 and 5500 rpm.

Yours works but then dies.
As in the main works and then sucks all the fuel out of the chamber faster than it can refill.


So check for air leaks to start.

Another way to help see if it's air or not is to use clear vinyl line from the tank to the carb directly and same for the return.

Then look for air bubbles while riding. Make a longer loop so that you can see the fuel move.
I just made it long enough that I could zip tie it to the seat hook for both lines.

Thanks Mekanix. I did not use any of the springs with the kit but I will mention during my carb rebuild I replaced 1 of the springs with a spring replacement from jetworld. During my pop off test one of the carbs was really low. I ordered a new spring and got them both popping off at 32psi. I did try bending the arm slightly to adjust pop off currectly but if memory serves one was popping at like 36 and one was popping below 30.

 

[digital sol]

Edit: found my original post from my rebuild thread

"Pop off goal is 30-33 psi
Test results show the following
PTO: 36PSI
MAG: 26PSI

-both 1.5 valves & silver springs
-installed new replacement valves & same results
-ordering some spring options tonight to tinker & try to get them on spec"

If memory serves I replaced 1 arm and one spring "black spring" to get them both popping 32-34. Used an oem kit from OSD

 

[digital sol]

I pulled the fuel filter and it was filled with gas and clean. The filter is new but the ring also looked good. I did squeeze the throttle and check for a hiss. I read somewhere that it should hiss when pulling throttle. I didnt hear anything but it was really loud "boats/waves/people/kids/music" you name it. Im going to swing by down in a few hours when the lake is dead to test. I verified the carb setting as well, 1 turn out low settings and 1/2 high pto. I checked all the metal couplers and everything is super snug. I did notice one thing..there is a three way vent valve area in the front near the fuel filter and none of the lines off this valve have clamps on them. Not sure how snug vent lines really need to be but if there is a chance this can let air in the fuel system I will grab some clamps tonight and toss them on tomorrow.

I might also remove the inline fuel filter and run a barb fitting there to make sure the inline filter isnt restricting flow

 

[seadoosnipe]

I haven't been in the forum in a while, raising kids and too busy on the river, but you have a GTX, my fav ski, so I got to put my two cents in.

You said when you raised the seat, you saw smoke, but when you ran for a bit, it stopped. You also said, it would run for a minute, then fall flat. You have and exhaust leak, and left unchecked, those problems you are mentioning, are the primary cause of your problem. With an exhaust leak, your ski is burning what oxygen it can get from the air, then when the hull fills with carbon monoxide, the ski can no longer get air for combustion, causing you to lose power, and starve the motor for air. Even if you can't find that leak, it is putting the gasses inside. Ride for a long period with y our rear seat and storage box removed, to ensure you are receiving the air you need for proper combustion.

The picture your holding up of your plug, looks good. DO NOT adjust your high speed jet. That is actually a bypass, and should not ever be adjusted, unless your riding somewhere like Colorado, where your elevation changes.

Your adjustment to the RPM is located on the MAG carb, accessed from the front side, at an angle, through the bracket. You should be able to get a short screwdriver through it, to adjust it.

Oil injection. You are not doing yourself any favors by premixing this motor. It was designed to run injected, and premixed will cause fouling of your plugs. The reason: Put your thinking cap on. When you premix, lets say, 40:1, then that means, your engine is always burning that oil, at that ratio. In reality, that engine does not need that much oil to operate. When you are at WOT, then your oil injection system is putting in about a 40:1 mixture. But, as you slow down, your ratio changes. By the time you come down to idle, your oil mixture could be 1 part oil, 60:1, because at idle, you don't need as much oil. That is why you are smoking at idle, and probably, fouling plugs. I have 2 GTX's, one XP, and 2 Challenger jet boats, and all run the 787, and not one of them is premixed. Two of my craft are running the original engine, because it's always been taken care of, running direct oil injection, to keep from gumming up the cylinders.

I'm attaching a pix of a chart, so you can read your plugs. I have one in the forum somewhere, but only God knows where it is, cause I have been out for a pretty good time. Oh, Also.... important! Your carbs run in 3 phases. When you are at idle, the Mikuni's are running on your idle and low speed jets. When you start to speed up, you'll to to transition. Which is a combo of the high and low speed jets, which is about 4 or 5k rpm. When you go WOT, your running solely on your high speed jets. If the ski/boat isn't running well at WOT, run for about 5 or 10 minutes, then without slowing down, pull your DESS and let the boat come to a stop, then read your plugs right then. Don't let them cool off. Use a rag to hold onto them. This will tell you what your high speed jet is running like. Your premixed, don't expect to see a good read at lower RPM's.

 

[digital sol]

I haven't been in the forum in a while, raising kids and too busy on the river, but you have a GTX, my fav ski, so I got to put my two cents in.

You said when you raised the seat, you saw smoke, but when you ran for a bit, it stopped. You also said, it would run for a minute, then fall flat. You have and exhaust leak, and left unchecked, those problems you are mentioning, are the primary cause of your problem. With an exhaust leak, your ski is burning what oxygen it can get from the air, then when the hull fills with carbon monoxide, the ski can no longer get air for combustion, causing you to lose power, and starve the motor for air. Even if you can't find that leak, it is putting the gasses inside. Ride for a long period with y our rear seat and storage box removed, to ensure you are receiving the air you need for proper combustion.

The picture your holding up of your plug, looks good. DO NOT adjust your high speed jet. That is actually a bypass, and should not ever be adjusted, unless your riding somewhere like Colorado, where your elevation changes.

Your adjustment to the RPM is located on the MAG carb, accessed from the front side, at an angle, through the bracket. You should be able to get a short screwdriver through it, to adjust it.

Oil injection. You are not doing yourself any favors by premixing this motor. It was designed to run injected, and premixed will cause fouling of your plugs. The reason: Put your thinking cap on. When you premix, lets say, 40:1, then that means, your engine is always burning that oil, at that ratio. In reality, that engine does not need that much oil to operate. When you are at WOT, then your oil injection system is putting in about a 40:1 mixture. But, as you slow down, your ratio changes. By the time you come down to idle, your oil mixture could be 1 part oil, 60:1, because at idle, you don't need as much oil. That is why you are smoking at idle, and probably, fouling plugs. I have 2 GTX's, one XP, and 2 Challenger jet boats, and all run the 787, and not one of them is premixed. Two of my craft are running the original engine, because it's always been taken care of, running direct oil injection, to keep from gumming up the cylinders.

I'm attaching a pix of a chart, so you can read your plugs. I have one in the forum somewhere, but only God knows where it is, cause I have been out for a pretty good time. Oh, Also.... important! Your carbs run in 3 phases. When you are at idle, the Mikuni's are running on your idle and low speed jets. When you start to speed up, you'll to to transition. Which is a combo of the high and low speed jets, which is about 4 or 5k rpm. When you go WOT, your running solely on your high speed jets. If the ski/boat isn't running well at WOT, run for about 5 or 10 minutes, then without slowing down, pull your DESS and let the boat come to a stop, then read your plugs right then. Don't let them cool off. Use a rag to hold onto them. This will tell you what your high speed jet is running like. Your premixed, don't expect to see a good read at lower RPM's.View attachment 36245View attachment 36245

Thanks so much for the reply!

Yes, when I first dipped the ski in the water and started it up I saw a little bit of smoke from the exhaust, it appeared to be from the clamp area but after a minute or two the smoke was gone. I recently painted all these parts as well so I wasnt sure if maybe it was just the exhaust heating up and burning either rtv stuff off or maybe paint. I havnt seen smoke inside the hull of the sea doo ever since that first start up. I also did tighten up the clamp around the exhaust a smidge just in case.

Can I spray fogging oil around the clamp & check for rpm fluctuations? I sprayed some around the carbs earlier but did not see any change in rpm. I went ahead and bumped up the idle speed to 1500 and its on the dime now as far as idle goes.

Just to verify you want me to do a plug chop at partial throttle just around the 4-5k range? The ski seems to bog pretty bad when I hit WOT now. Sometimes taking a wide turn I can mash the throttle and see it hit 6k+ rpms but immediately once I plane on the water it drops to 5k ish and bogs down hard. Thanks so much for that chart. The plugs from doing a WOT plug chop the first day looked like the "best" picture. They are a light brown color.

I hear you on the oil pump. I will most likely buy a new pump and throw it on for next summer but the last shop that worked on it pulled the pump and said it was the cause of the last engine failure. I just figured for now its one less thing to worry about but I totally understand I am going to be spending more cash on oil and fogging out plugs more often. Ultimately I do plan on putting the oil pump back on once everything is squared away and she is back to being reliable.

Thanks so much for your time its really appreciated! You guys have always been super knowledgeable throughout my entire restoration. Ill do a 4k-5k rpm plug chop tomorrow and verify the readings.

 

[seadoosnipe]

Don't do anything until you try these two steps first. Start the ski, and run it/ride it, till you have the problems. When you have these problems, I feel your sucking in carbon monoxide and it's causing your motor to run like crap.

Now, take off the seat. It's a GTX, take off the back seat and take out the storage box, to expose the engine compartment to a constant supply of fresh air. Now, ride it till that same problem occurs again. If that problem does not come back, then your entire problem will be caused by your exhaust leak. I have seen this shut down many, many skis. People don't realize, it's not like a car. These hulls are really tight. You MUST have a constant supply of fresh air.

 

[Mickirig1]

You may be sucking air into the fuel system. Look at the gasket on the water / fuel filter in front hatch area if you have one. Get a piece of 1/4 inch brake line and 2 clamps. Bypass it and see if you get results. You can do leak tests with a pop off tester. Procedure is in the service manual. It also address's vents and check valves when you test it. The carb screws should be set to factory spec's. The low speed is just changed to get a smooth idle. The idle speed is set with the idle speed screw.
Do you get the hiss when you take gas cap off? If not this can be a sign you have an air leak.

 

[soccerdad]

Another way to help see if it's air or not is to use clear vinyl line from the tank to the carb directly and same for the return.

Then look for air bubbles while riding. Make a longer loop so that you can see the fuel move.
I just made it long enough that I could zip tie it to the seat hook for both lines.

This is a great test and will take the entire question of air leaks out of the equation.

 

[AdamXP800]

I haven't been in the forum in a while, raising kids and too busy on the river, but you have a GTX, my fav ski, so I got to put my two cents in.

You said when you raised the seat, you saw smoke, but when you ran for a bit, it stopped. You also said, it would run for a minute, then fall flat. You have and exhaust leak, and left unchecked, those problems you are mentioning, are the primary cause of your problem. With an exhaust leak, your ski is burning what oxygen it can get from the air, then when the hull fills with carbon monoxide, the ski can no longer get air for combustion, causing you to lose power, and starve the motor for air. Even if you can't find that leak, it is putting the gasses inside. Ride for a long period with y our rear seat and storage box removed, to ensure you are receiving the air you need for proper combustion.

The picture your holding up of your plug, looks good. DO NOT adjust your high speed jet. That is actually a bypass, and should not ever be adjusted, unless your riding somewhere like Colorado, where your elevation changes.

Your adjustment to the RPM is located on the MAG carb, accessed from the front side, at an angle, through the bracket. You should be able to get a short screwdriver through it, to adjust it.

Oil injection. You are not doing yourself any favors by premixing this motor. It was designed to run injected, and premixed will cause fouling of your plugs. The reason: Put your thinking cap on. When you premix, lets say, 40:1, then that means, your engine is always burning that oil, at that ratio. In reality, that engine does not need that much oil to operate. When you are at WOT, then your oil injection system is putting in about a 40:1 mixture. But, as you slow down, your ratio changes. By the time you come down to idle, your oil mixture could be 1 part oil, 60:1, because at idle, you don't need as much oil. That is why you are smoking at idle, and probably, fouling plugs. I have 2 GTX's, one XP, and 2 Challenger jet boats, and all run the 787, and not one of them is premixed. Two of my craft are running the original engine, because it's always been taken care of, running direct oil injection, to keep from gumming up the cylinders.

I'm attaching a pix of a chart, so you can read your plugs. I have one in the forum somewhere, but only God knows where it is, cause I have been out for a pretty good time. Oh, Also.... important! Your carbs run in 3 phases. When you are at idle, the Mikuni's are running on your idle and low speed jets. When you start to speed up, you'll to to transition. Which is a combo of the high and low speed jets, which is about 4 or 5k rpm. When you go WOT, your running solely on your high speed jets. If the ski/boat isn't running well at WOT, run for about 5 or 10 minutes, then without slowing down, pull your DESS and let the boat come to a stop, then read your plugs right then. Don't let them cool off. Use a rag to hold onto them. This will tell you what your high speed jet is running like. Your premixed, don't expect to see a good read at lower RPM's.View attachment 36245View attachment 36245

I am not advocating premix but I do premix(have my last 2 787's) due to suspect pumps. Previous owner did no maintenance. I have not once fouled a plug. How many boats,etc... use premix? Do you hear of these constantly fouling plugs?

 

[digital sol]

You may be sucking air into the fuel system. Look at the gasket on the water / fuel filter in front hatch area if you have one. Get a piece of 1/4 inch brake line and 2 clamps. Bypass it and see if you get results. You can do leak tests with a pop off tester. Procedure is in the service manual. It also address's vents and check valves when you test it. The carb screws should be set to factory spec's. The low speed is just changed to get a smooth idle. The idle speed is set with the idle speed screw.
Do you get the hiss when you take gas cap off? If not this can be a sign you have an air leak.

Thanks fellas, I bought 10ft of clear tubing to test with. I am going to run the suggested test and report back once its done raining. Thanks so much for all the suggestions and help!

First I will open the gas cap and check for the hiss/pressure relief
Second I will run it with the seats off to verify issue still exist
Third I will replace the line from the fuel tank and run it straight to the carb bypassing the selector, and filter as well as replace the return cable with clear hose "fuel tank was just cleaned out completely and its brand new gas so I am not too worried about a filter being in place for this testing as basically everything is clean and brand new"

Then I will take her for a ride and check the lines for air as I ride & see how it runs. *In hindsight when I replaced all the fuel lines I should have just used clear lines to begin with instead of the black lines...down the road I will replace all fuel lines with clear lines for future purposes but for now vinyl tubing for testing*. 20-25ft of clear fuel lines is only like $12 on amazon. Or its $4 a ft for yellow/clearish tubing at oreilly's. I got clear vinyl non fuel rated lines for 30 cents a foot at ace hardware for testing.

Edit: I am also checking the manual now for that test you mentioned earlier. I do have my pop off tester here and a foot pump I can test with

 

[Mekanix]

You want the black line in the end. Vinyl line will get hard over time so its only really good for testing unless you get tygon line which is the 4$ a foot stuff.

 

[digital sol]

Hey guys, unfortuntely due to weather on the lake today I didnt get much time on the sea doo however I did the following
-installed fresh plugs
-rode with seat off>it runs smooth below 5k but 5k+ it still sputtered after it used up the fuel, it definately feels like fuel starvation so I think we are on to something

I removed the inline filter and retested because I noticed the filter was nearly empty after going WOT. Also I wanted to note that when I un-screw the gas cap i did NOT hear a hiss or that suction noise I usually always hear when removing the gas cap in the past. It finally stopped raining near dark but I went ahead and did the following
-ran clear hose from the gas tank straight to the carb, I left the oil line connected to everything but drained as much gas out of the old lines as possible
-ran clear hose from the gas tank to the vent line, also removed this line for now

I do have a couple questions
1) Do I need to do anything with the res line? I did NOT disconnect the original lines from the selector but wasnt sure how the res actually works on these.
2) This valve needs to remain open right? Its on top of the oil tank and the line has oil in it to the bottom of the motor on the exhaust side but there is also a large air pocket near the top of the hose. I thought that valve is suppose to open & take that air out of the line?
3) Do the air vent hoses in front of the selector connected using a 3 way plastic coupler need to have fittings on them? Clamps basically

Old Lines laying in the front..these ends were on the pump

Three way plastic piece with vent hoses. Do these need clamps??


Clear hose from tank to vent line

Clear hose from tank to the feed on the carbs. Note: I left a small section of black hose connected to the carb because i have a hard time getting the line off without removing some parts. The line was already cut because I was running an inline filter there after the oem fuel filter as well. Its bypassed with a 1/4 to 1/4 insert. Plenty of line there so I can check the fuel..hopefully its not too much to cause any issues




Side note; Weather sucked so I worked on my dad's boat. Its the same age as me LOL. You can see how yellow it is from where the rail brackets used to lay

 

[digital sol]

It wont let me edit my post but I meant to say *fuel* line not oil line. I get a server error while trying to edit my post so figured I would mention it here so I don't confuse anyone.

"-ran clear hose from the gas tank straight to the carb, I left the oil line connected to everything but drained as much gas out of the old lines as possible"

 

[Mekanix]

Nice work.
Leave the fuel selector off so no feel drains out of the lines.

In the tank there are two tubes. One is long and one is short. The short one is your on line and the long one is your reserve line.
Both lines go to the fuel selector, then one line comes from the fuel selector and it goes to the water seperator. Then from there it goes to the carb.

On the sending unit it will have RES, ON, RET, VENT writen on the side of it.

The other line from the carb to the tank connects to the RET port.

The fuel system on this thing is like an automotive system. Any fuel that isn't used is sent back to the tank.



That air bubble in the oil tank line is normal. And the thing on top of the tank is the oil level sender. Also that check valve on the top is a one way valve used for pressure testing the oil sydtem.
The oil level in that line will rise and fall with your oil level.

 

[Mekanix]

Yeah the site is messing up for me too.

You might want to pull some fuel into the supply line at least half to 3/4 of the way to help the fuel pump along.
This should reduce the wear on the starter while it's priming.

 

[Mekanix]

3 way thing is your vent and tank pressure relief lines. Yes they need clamps.
On one end you have a one way in check valve that let's air into the tank and on the other end there is a pressure relief outflow valve.
The other end of that 3 way goes to the tank VENT.

The thing in the tank is a sender unit. No pump inside of that.

 

[digital sol]

Awesome thanks so much! Yea good call I will pull some gas through the tube before starting to try and start it. I will throw clamps on those lines in the morning for sure. Possible that's causing the issue this entire time? Ha, as dumb as it is it sure would be nice if that was the root cause lol.

 

[soccerdad]

If you have one of those hand powered vacuum brake bleeders, you can use it to suck fuel all the way to the carbs. I found it to be a handy tool. http://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-69328.html It keeps you from cranking and cranking to get it started.