Acceleration problem

[ProbeGT]

Since i don't have anymore answers in the premium section I'll try myself here.

I'll quote all I've written but don't care about the throttle cables, it's not my main concern for the moment.

98 speedster 2X 787

When i floor both engines at the same time, left engine (Original one) revs quickly to 7000RPM. Right engine revs up to 5500-6000 then kinda bogs and then revs to 7000RPM.

Today i syncronised both engine with the shop manual, i adjusted throttle cable, adjusted low speed screw, adjusted acceleration pump. Didn,t touch the high speed screw since i wasn't in water.

God those boats are painful to work on... If what i did doesn,t solve the problem, what can be the cause?

Right engine has been rebuilded 155PSI on each, left engine is original, 150PSI on each. Fuel is fresh.

ohh and sometimes, when I floor both engine, left one stalls for no reason, I think it might have been the acceleration pump that sprays too soon?

Should i touch the High speed screw? it's very hard to access with airbox in place (as everything else) I'll put new plugs tomorrow and hold WOT for a minute or 2 to look at the mixture.

Did the test...

Held WOT for about 1.5 minute

All 4 plugs are a nice chocolate brown, no big oil deposits. Engine still hesitate after setting the carbs as the shop manual says.

I also have a problem with throttle syncronisation. up to 3000RPM, both handles are at the same position, and 6000RPM and up, both handles are at the same position.

there's a huge gap in the left engine throttle response. I must give a good inch more throttle than the right one to maintain the same engine speed for both. Also my opas system doesn't work at all but I didn't check cables yet. Also sometimes, the drive selector switch back to neutral when i cut back my left engine's speed. Like if they stick together sometimes. Should I change my fuel cables ?

Thanx for all your help.

Adjusted the accleration pump correctly and double checked everything then

Ok so I went on the water today.

I adjusted the acceleration pump correctly, it opens as soon as you touch the throttle and the adjustment is made so it Fully pushes the diaphragm when engaged and it fully retract when disengaged. Engine is better responding but it still bog down when I floor it. I tried to give 1/4 turn richer on both low speed screw, it's worse. I gave 1/4 turn more lean, worse again, 1.5 turn is really the best setting.

What's better now is once the engine has revved hard, it will jump to 7000RPM when i floor it again. But if I hold idle for more than 15-20 seconds, it will bog. Another thing I've discovered today is that even if I hold 3500 or even 4000RPM for a long time, then floor it, it will again stall at 5000 for a good second or 2 then jump to 7000.

Here's a video that shows what it does I'm holding it to 3500 then floor both engines, you can clearly hear the left one responding instantly then the other finally wakes-up.

http://www.youtube.com/user/ProbeGT2.../0/zpP-S766KRs

I don't have the grey fuel lines but I seem to have gray oil lines near the engine. Most of my lines are black. Now I really don,t know what to do. The engine start instantly, revs freely up to 5000, WOT runs great, it's just that damn stalling when I hold idle or 1/3 throttle for a long time... I fear that rebulding the carb wouldn't fix the problem, it seems to be something else than dirt in the carb.

One thing I didn't do is removing the spark arrestor and look if both jets sprays correctly. I think yes since it revs hard when i floor it after a short period of time WOT.

I just wanna make sure it's not the acceleration pump before I dismantle the carbs. When I press on it, i can hear and see the fuel spraying, even If i press it 2-3 times. What could be the problem???

 

[seadooya]

rave valves clean? dismantle the fuel pump thats located on the tuned pipe, and clean it? clear out/replace the grey pulse lines and clear out the pulse fitting off the case?

I'd set the pto-hsa to atleast 1/8-1/4 turn from 0. the one that reacts quik, may be a wear ring issue/impellor issue also. Tyhe play in the throtte assy, could be a linkage loose at carbs, back the nut some, to tighten her up. Replace the fuel filter/s?...

 

[TJ198]

Your link doesn't work for me but I was able to figure it out.

http://www.youtube.com/user/ProbeGT2#p/a/u/0/zpP-S766KRs

 

[ProbeGT]

rave valves clean? dismantle the fuel pump thats located on the tuned pipe, and clean it? clear out/replace the grey pulse lines and clear out the pulse fitting off the case?

I'd set the pto-hsa to atleast 1/8-1/4 turn from 0. the one that reacts quik, may be a wear ring issue/impellor issue also. Tyhe play in the throtte assy, could be a linkage loose at carbs, back the nut some, to tighten her up. Replace the fuel filter/s?...

I didn't clean the raves but I've checked them when i changed my oils in the pump, they all move very freely.

Checked my pump clearances when i changed the oils, both are below 0.018" I didn't clean/replace fuel pump/filter because when both engines runs WOT (once peak RPM is achieved) they all runs perfectly for as long as i hold them. no signs of starvation. Plugs are nice chocolate brown, engine don't seem to overheat. They key here is that it do it when i hold idle for more than 10 seconds, and/or hold RPM below 4500RPM for more than 10 seconds.

Are you telling me that they aren't supposed to jump immediatly to 7000 and that I might have cavitation?

EDIT : also i didn't touch the high speed screw because according to my plugs, the mixture seems perfect (and RPM is in the good running range)

Can you explain why the fuel pump would cause an acceleration problem like that, i don't understand how it could be the problem.

 

[NapaMatt]

Sounds Liek you Need to look in to FUEL Issue Fuel Pump going to Both Engines!!!

my .02

 

[Phildoo]

You ever resolve this issue?

 

[ProbeGT]

nope. I don't think it's fuel pressure or pump because the engine just keep going at WOT. I don't think on an acceleration it would completely loose fuel pressure.

I'm even wondering if it's not normal and that its my other engine who cavitates upon deadstop acceleration... Who knows...

But since the boat runs very well apart from this point, and that i can't find the real problem before dismantling everything, i just run it like that.

 

[Phildoo]

I checked out your video also. Fix that metallic sound? Im having an acceleration and idling issue with one engine so thinking its a carb problem

 

[ProbeGT]

apparently the ratling noise is normal because there's no force pushing agaisnt the driving shaft. I tought these pumps had anti-ratling system but it seems that it doesn't work very well, it does it even on water but only when i'm idling. Mine doesn't have any idling issue, but i have de-synchronisation of the engines between 3000 and 6000RPM I need to give a lot more gas on the left engine to match the right one. RPM is very steppy on the left one VS the right one. I need to be very gentle on the throttle unlike the right one were it's very easy to setup a RPM and maintain it.

 

[Phildoo]

I have the exact same rpm issue you have, so we are "literally" in the same boat.
There is some rattling metallic noise when not in water which provides pressure against the propulsion system. I get that too, but I had it in the low to mid range rpm's.
Until today.
I just installed new impellers and wear rings, but also rebuilt the jet pumps since they were out and the metallic sound is now gone so perhaps its time to do that on yours?
After i figured out how to do the first one, it took 4 minutes to do the second one.
It is so easy..a caveman can do it.
Seriously.

 

[ProbeGT]

maybe you're right, actually i had one stator broken. The dealer who had rebuilted the rigth engine broke the stator where the top right bolt would hold. the stator was only held by 3 bolts and i bought the boat like that so i ordered a new stator, i'll check if it runs right. And i'll probably buy pumps rebuilt kits with new carbon seal to make sure everything's all right. And if I still have my acceleration problem, I'll do the carbs. Its just so much pain in the A$$ working on those carbs, makes me want to never touch them again! lol.

 

[seadooya]

you ever check on the raves?

are the water regulators, set flush with tops of caps?

Is the red dots for the raves, turned/bottomed out?

 

[Phildoo]

I know nothing about messing with the rave valves, How do you check/clean them?

 

[ProbeGT]

you ever check on the raves?

are the water regulators, set flush with tops of caps?

Is the red dots for the raves, turned/bottomed out?

1- yes they move very freelly
2- didn'T check but i don't think so
3- I don't think they are turned up to locking position, didn't touch the adujstment.

 

[ProbeGT]

Well, I changed my reverse cable today and while I was dirty I decided to give a try on those rave valve. Even tho they were moving freely when i dismantled them is was a mess. a thick coat of carbon. cleaned all 4.

It solved one problem but not the one I tought it would. Now my throttles are perfectly sync. I also gained Idle RPM (really don't know why, i'll have to re-adjust my idle speed screws) But that damn engine still bogs when i floor it. I also sucked up some weed today, overheated an exausth pipe but I noticed it before big damage occur. I loosened the water regulator springs so the bolts are flush with the cap. They seem to run cooler now, didn't solve acceleration problem. I also tried to loosen the rave springs on the bogus engine, didn't solved anything.

Today I sucked my tow rope. I removed it but It has damaged some of the blue plastic on the driveshaft. Can I still run it until I change it or this part is very important? It only looks like a kind on guide to me so the shaft doesn't spin on the hull. Only the last 3-4 inches are damaged.

Ohh and while i had weeds, the bogus engine would rev to the limiter in a lightning, so it only bogs when it works against water.

 

[RivaRat:)]

Just bought a used one. Same problem as yours.

I just picked up my boat yesterday. Sad to say it was so dirty I spent more time cleaning it, than looking in the engine compartment. I know for a fact that it was run up on sand bars on occasion. When I crawled under the boat i saw the impellers were chewed a little but overall good condition. definitely replacing them in the near future. When I put it in the water, ran good. The motor behind the drivers side, dogs. Just like you guys are talking about. When its half throttle, doggy engine is running 7-8 hundred rpm slower than good side. I'd love to know if you found the solution to your problem. I owned one 93xp years ago... but its been so long. I know absolutely nothing about this boat. Supposedly the engines were both rebuilt 2 years ago, but as to what extent I have no clue. Previous owner put the fuel stabilizer, "stable" in it I've heard this gums up carbs. Where do I even start, I'm fairly green.