Run'n lean on the right side motor. Any ideas?

[ORION '95 Speedster]

So I have a boat that was sit'n for a long time. Used a hand pump to prime the fuel lines. Got the first motor running good, but the 2nd motor runs lean. Hard to start, wandering RPM's, pinging, 90% choke makes it run better, etc etc.

Bottom line is that the motor is running lean. Fuel switch in the on/res function makes no difference. Fuel filter is consistently full. Would prefer not to rebuild the carb. Any ideas what might be some easy quick thing to check? Any internal filters in the carb? A fuel pump test? Ideas?

 

[BoLongo]

You have to figure out if it is an air leak or starved for fuel.

The first clue of sitting for a while points to a leaking crank seal, but I don't think the leak would be large enough to cause the need for 90% choke.

If you are pinging, that would have to be bad gas from sitting or you are developing a hot spot in the combustion chamber which is causing pre-ignition from being too lean. If that is the case, the engine is imploding.

Wandering RPM would have to be leaking fuel in the carburetor probably a bad needle and seat.

Pulling the choke could also cause the pulse fuel pump to perform better if you have a compression issue, or you are running the carbs without the spark arrestors.

I would rebuild the carbs and do a pressure test.

 

[ORION '95 Speedster]

I don't have anything on the carbs at all. Choke plate is fully exposed. Would that cause these motors to run poorly? I have seen other engine run poorly without the air box attached. I will try putting everything back on and try running it. With low RPM's it wants to stall. It will run ok at 2k for a bit, then RPMS will drop down and it will die unless I pull the choke and or giving it more throttle. If I fiddle with the choke, and mess with the throttle, it will run forever but doesn't really sound right. Sounds lean.

 

[BoLongo]

The pulse fuel pump needs the crankcase pressure to fluctuate When you don't have the spark arrestors on it affects the crankcase pressure which affects how well the pulse pump works. I just run the spark arrestor without the plastic housing. That could be part of the problem, but it sounds like you have other issues as well. Did you drain the old gas in the gas tank?

 

[ORION '95 Speedster]

I drained the old fuel, which was REALLY old. I used rags to soak up what was left. There could have been a very small amount left in the tank if any. I added 5 gallons of premium non-ethanol fuel, with the proper amount of Sta-Bil 360 Marine additive. The other engine is using the same fuel without any problems. I was thinking it might have something to do with the pulse pump, but it must be working somewhat, as it is drawing fuel out of the fuel tank. If I empty the filter housing, and start the engine for 5-10 seconds, the filter housing is full of fuel. I know how to do this properly, but I'm being lazy and looking for shortcuts. What I should really so is swap the carbs/fuel pump over from the other motor, and I bet it would run great. If not >> crank seal. I just don't feel like swapping carbs though. I will start with putting the spark arrestor back on in the morning.

 

[BoLongo]

I would pull the head to look in the cylinders. If only one of the cylinders are scored on the exhaust side, you can be somewhat sure it's a crank seal.

 

[ORION '95 Speedster]

If it comes down to that I will, but I would prefer not to pull the head unless its needed. I would swap carbs first. Are there any internal carb filters that you know of?

 

[BoLongo]

Yes, they're inside the carbs, but you might as well rebuild the carbs if you take the time to get to them. Alway. Always use the original Mikuni rebuild kits.

 

[XP 787]

If you have an air leak that motor will "run away" meaning it will hit full rpms and you cant shut it down even if you pull the key. If this happens pull the key and choke.

Have the carbs ever been rebuilt? If not pull them and do it as this has to be done anyway. Replace needle and seat also. Im sure you know that the engine gets its oil from fuel supply so no fuel means no oil and now you are stuck replacing the motor and still having to rebuild the carbs. There is a small filter inside the carb which usually becomes clogged because of the gray fuel lines.

 

[ORION '95 Speedster]

During this initial testing, I'm running 40:1 pre-mix in the gas tank and I also replaced the oil lines. In addition, I have the oil control arm zip-tied in the "full open" position. If putting the spark arrestor back on doesn't solve the problem, I will check the carb fuel filter, and then swap carbs from the other motor. If swapping carbs fixes the problem, I will rebuild the original carb with a kit. Thanks for all the input, I will keep ya posted. Testing later this morning.

 

[XP 787]

ok good luck

 

[racerxxx]

To quote you "I'm being lazy and looking for shortcuts", list the boat on Craigslist or letgo. Cut your loss, if your not willing to put the time into it, why have it at all.

Why are you running 40:1 and have the oil pump zip tied wide open. That's easy to much oil. Your complicating what your doing. Rebuild the carbs, put the air boxes back on, set the out of water idle at 3k and go from there, until then you might as well just bang your head on the wall. Sorry to be harsh, just hate setting guys chase their butt

 

[ORION '95 Speedster]

Don't get me wrong, I will rebuild the whole motor if needed, but I'm looking for simple fixes first. If it aint broke, dont fix it. For instance if BoLongo is correct, and the spark arrestor is the problem, I can avoid rebuilding the carb, pulling the head, etc. I may have to rebuild the carb, but Im not going to unless it warranted. The other motor runs great, and all I had to do was fog the motor, prime the fuel system and crank it over, doesn't need a carb rebuild at all. Start with the easy stuff and work your way up from there. For instance, when I noticed this motor was running lean, I first checked to make sure there was gas in the fuel tank rather than tearing into the motor. Im running 40:1 in the fuel tank, because I have no idea if the injection system even works at this point, and even if it does, the lines are full of air because I just replaced them. And even if all that stuff is ok, is the pump adjusted correctly? Running the 40:1 is too much oil, assuming the pumps are bled and working. I'm not to that point yet. Im breathing life back into some motors that have sat for years, so I am taking all precautions. After I verify the pumps work, and get everything running correctly, I will not run a pre-mix in the tank. I have been a mechanic for a long time, but I work on all kinds of things. Tractors, refrigerators, cars, boats, computers, welding, fabrication, go karts, quads, etc, however I do not specialize in one specific thing. I don't know everything there is to know about a 1995 Seadoo Speedster and I don't know everything about a Cessna 172 air plane, but I can work on both. Currently I'm into this boat $450 including the trailer, and both motors run with 150 lbs on each cylinder. I don't want to go hog wild and start rebuilding everything I can find. I want to spend as little time and money as I can to get the best results, that's the whole idea. It would be easy to go buy a brand new boat, but whats the fun in that? If I can get this thing up and running on the water, with all the upgrades and fixes for 5 or 6 hundred total, and not have a million hours labor into it, THAT would be way more awesome than going down to the stealership and buying a brand new boat that I don't even get to work on.

 

[ORION '95 Speedster]

racerxxx, I agree with you on this: "if your not willing to put the time into it, why have it at all."

 

[racerxxx]

Have the carbs even been touched internally by you yet? If not that is the first thing everyone does here after a comp test, a full rebuild of the fuel system.

 

[ORION '95 Speedster]

No, i'm not going into the carbs unless its needed. Age alone is not a default rebuild, in my book. I have rebuild the fuel system on jet skis before, and sometimes they needed it, and sometimes everything in the carb was fine, and it was a waste of time. At this point, i'm not counting out the possibility, but i'm not doing it by default either. On the motor that is not running correctly, it will likely have a carb rebuild, but not until other possibilities have been eliminated. Sometimes people guess, and fix something that was not broken and in the process mess up something that was working fine, then there are two problems making it a thousand times harder to fix. My other engine runs perfectly, Im certainly not going to start fiddling around with the carb on that one just because I don't know when it was last done. I don't disagree with you racerxxx, I am simply taking a different route. I think both ways are sound.

 

[racerxxx]

Sounds good, I wish you the best. I've been around these skis and boats for years, fuel system rebuild is dire on them, especially after sitting.

 

[ORION '95 Speedster]

I appreciate your input, I will keep that in mind.