JB: need your worldly wisdom!

[busterb]

My brother in law and I took out his little 15' trihull last night with the 76' 75 hp rude on it. We thought we had the wrong size prop a couple of weeks ago but Dhadley told me it was the right size. What's happening is the motor is apparantly getting too much gas because it won't rev past 3800-4000 rpms wide open. Good compression, (rebuilt PH) good spark on all 3, etc. Here is what happened last night. We ran out of gas in one of the 6 gallon tanks, and when the motor started running out it all of the sudden picked up and ran at 5000+ rpms and then starved of fuel totally. Am I right in assuming this would be worn out high speed jets causing the motor to be bogged by too much gas? Also- we dropped a cylinder which would try to fire intermittently last night. Any ideas on it? Thank you in advance!

 

[ehenry]

Re: JB: need your worldly wisdom!

It could be that your fuel pump was weak then finally shot crapps. Would the engine run while you were pumping your primer bulb?

 

[Bob_VT]

Re: JB: need your worldly wisdom!

That cylinder may have been "dropped" all along which would account for the low revs. As for the running up to 5000 when you ran out of fuel that is also common. I would inspect that dropped cylinder and research that first.<br /><br />JB is "out of town" for a bit.<br /><br />Bob

 

[12Footer]

Re: JB: need your worldly wisdom!

Yes, compression test first off,to try to figure-out what is going down with that cylinder. Plus, low compression would make the fuel pump pump fuel poorly.<br />Check condition of primer bulb.If it is real soft, or collapses, try loosening the cap on the tank,to see if it is a benting problem.<br />And JB will be back in a few daze.

 

[busterb]

Re: JB: need your worldly wisdom!

Woohoo! I got the problem solved! Pulled the cover off the carbs last night in the driveway fully anticipating a full carb rebuild and looked at the butterflys. Lo and behold, the **** throttle linkage was totally out of wack. The top 2 butterflys were only opening 3/4, and the bottom was going past horizontal and closing all the way back up!!!! We adjusted the linkage and headed to the lake. Motor fired right up and took off like a scalded cat. We decarboned it after we ran it a while with quicksilver engine tuner which helped even more. Man I love the rush you get when you solve a problem like that! Thanks for everybody's advice.