Engine RPM

[mlcrew94]

Ok someone please explain this to me I have a 97 Sea-Doo challenger 1800 with the twin 787 engines. I’m having troubles with the carbs I believe on one engine so I put it on the water today to see if I have got the problem fixed and when I go WOT both engines only rev to about 5k BUT when I open the engine hatch and go WOT the one engine will jump right up to the 7K but the other engine still won’t go past 5k. If I shut the engine hatch the other engine again won’t go past 5K. What could possible cause this? I mean why would it matter if the engine hatch is open or closed? Could it be to much smoke in the engine compartment? I had the blower on the entire time and the engines didn’t seem like they were really smoking. When I opened the engine hatch I wasn’t hit with any smoke.

 

[2x2smoke]

I think they say that CO2 and CO are colorless and odorless. Put a canary or a CO detector in the engine bay. Kidding aside, I think you describe textbook signs of an exhaust leak. Oxygen starvation with the hatch closed.

The engine draws fresh air from the two side hull intakes. The fan blows air out of one of them so running the fan might sort of choke off one of the air intakes as its blowing the air the wrong way. This gives me an idea for a new thread...

 

[Dr Honda]

Yep... when you have a problem and the hatch takes care of it... you have an exhaust leak. But PLEASE D NOT just try to tighten the bolts. That will just lead to broken bolts, and worse leaks. You can use soapy water, and spray around the joints to look for leaks. If you find one, remove the bolts, and replace the gaskets. The bolts are only torqued to 18 lb/ft. They need to be able to stretch, and contract as the engine parts get hot and cool. If you over tighten them... they will stretch past their "Spring" point, and the gasket will just get crushed and leak again.

BUT... I would still pop the carbs off, and clean them. AND, check the fuel select valve. (They go bad and cause issues too) On that note... did you try switching over to reserve and run?

 

[mlcrew94]

I do have an exhaust leak where the pipe head meets the pipe cone. I have a new copper gasket on order. I knew water was leaking out of it but I guess I never thought about the gasses that must be coming out also and it is right next to the intake of the engine being choked off. Ok so that explains the mystery. Lol. Is it possible that the same leak is my problem with the engine I think has carb problems? Would having that leak some how keep the engine from reaching full throttle? When I had it out yesterday like I said it would go to about 5k but after about 10 minutes anytime I tried throttling it up it would just die even with the hatch open. It would start right back up but would only idle at about 1k when before it was idling at 1500.