140 evenrude speed problems

[rlguns]

I have a 79' 140 Evinrude on a 17 foot stratus boat.The motor has just been rebuilt,I can only turn 4800 rpms and speed about 40 mph.I think that it should run faster.I have a hotfoot connected and it does carry the throttle all the way open. could someone please give me some advice.

 

[rlguns]

Re: 140 evenrude speed problems

I forgot to mention but it runs well -no misses , clean gas and clean tank . I have tried 13x19 prop and 21 pitch prop , same problem.

 

[Big Rod]

Re: 140 evenrude speed problems

Are all cylinders firing? Is timing fully advanced at W.O.T.? Is throttle stop adjustment correct? What kind of rpm change resulted from the prop change?...

 

[rlguns]

Re: 140 evenrude speed problems

All the cylinders are firing , don't know if timing is correct, throttle stop is correct .throttle is all the way open,motor seems to run fine no missing or cutting out . still cant figure it out.

 

[Big Rod]

Re: 140 evenrude speed problems

rlguns, At this time, you MUST focus on full advance timing for two reasons: #1- It could be whats holding you back. #2- Severe damage could result from detonation due to over advanced timing, especially if engine is actually overloaded.If you do not have specs. on timing for your engine, repost, we'll work you through it. Also, you did not mention what the prop change did...

 

[Daboss427]

Re: 140 evenrude speed problems

I'm having a similar problem, but I think mine is related to the timing. I have a 84 Johnson 100 HP. The idle speed is too fast and it's only turning around 4200 RPMS. It runs ok for a little while then seems to bog down. I don't have a clue how to set the timing or what to set it at. Can someone tell me where the adjustments are, and what to set the timing to. Can you use a automotive timing light etc. I've worked on a lot of cars but never an outboard so I'm at a complete loss. Thanks in advance for any help you can provide.