engine feeling like missing under load of plane

[bartdjunkman]

My compression is good. New plugs, link and sink conpleted and mechanic says my carbs look good. It runs perfect at idle and on top end it does great. It is that take off when it is under the greatest load it is turning around 3500 rpms and it almost acts like it is missing and then as it starts to get on plane it takes off and no more problems. I am trying to educate my self a little so if i take back to the mechanic i wont be totally ignorant. Thanks in advance.

 

[Daviet]

Re: engine feeling like missing under load of plane

It might be helpful if we knew what engine we were working on?

 

[kenmyfam]

Re: engine feeling like missing under load of plane

What boat, what motor and is this a new issue or has it been like this since you got it ????
Let's go from there.

 

[bartdjunkman]

Re: engine feeling like missing under load of plane

it is a 1987 evinrude xp 150. on a 18ft. ranger bass boat. It did this and my mechanic tuned up the boat and it did way better. After about four trips during the spring it started acting up. If i hit a few waves it comes out quicker and then it runs great. It also runs great at idle speeds. It is under that load of trying to come up on plane that it seems to me missing.

 

[kenmyfam]

Re: engine feeling like missing under load of plane

Do you know what your mechanic actually did to "tune up" the motor ???

 

[bartdjunkman]

Re: engine feeling like missing under load of plane

changed plugs, said my carbs were sticking cleaned them, did a link and sink, adjusted the timing.

 

[kenmyfam]

Re: engine feeling like missing under load of plane

What RPM are you running at WOT ???

 

[jlams73]

Re: engine feeling like missing under load of plane

This past weekend mine did the exact same thing. Please keep us posted as to what fixed your issue.

 

[bartdjunkman]

Re: engine feeling like missing under load of plane

wide open trimmed all out around 5500rpm. around 800-850 at idle.

 

[kenmyfam]

Re: engine feeling like missing under load of plane

How much weight are you carrying and where is it loaded ???
Does the power trim work and if so what is your routine for getting on plane ???
I would still suspect the carb's at this point.
My 2 cents.

 

[bartdjunkman]

Re: engine feeling like missing under load of plane

boat is 5 person 750lb. I had about 475 with gear and two guys. If the carbs were bad why would it run so good on top end and at idle. If this it that not so bad.

 

[kenmyfam]

Re: engine feeling like missing under load of plane

boat is 5 person 750lb. I had about 475 with gear and two guys. If the carbs were bad why would it run so good on top end and at idle. If this it that not so bad.

Have you tried re-arranging the weight ?? get some more weight up in the bow. Are you using the power trim ???

 

[kenmyfam]

Re: engine feeling like missing under load of plane

Not 100% on this motor but I think you have 3 jets per carb. Idle, intermediate and high speed. I would suspect the intermediate jet or jets may have a blockage or restriction.
Hopefully someone that knows this motor better than me will either confirm this or rule it out.

 

[bartdjunkman]

Re: engine feeling like missing under load of plane

i have tried to trim all the way down to all the way up. Nothing! I have tryed when putting a guy in the front, not no difference. If other boats are going by and i hit a few waves i am off to the races. I am wondering would a whale tail do any good? Could it be that the motor is sitting to low to the water and when taking of it could be to far in the water? Maybe i could raise it on my jack plate a few inches.

 

[kenmyfam]

Re: engine feeling like missing under load of plane

i have tried to trim all the way down to all the way up. Nothing! I have tryed when putting a guy in the front, not no difference. If other boats are going by and i hit a few waves i am off to the races. I am wondering would a whale tail do any good? Could it be that the motor is sitting to low to the water and when taking of it could be to far in the water? Maybe i could raise it on my jack plate a few inches.

If it was O.K. after being serviced and got worse then a whale tail will be of no value. What is your model number ??? what length is the shaft ?? is the cav plate even with the bottom of the hull ???
My 2 cents.

 

[bartdjunkman]

Re: engine feeling like missing under load of plane

How hard is rebuilding carbs or do you just buy new? or is this best left to the mechanic?

 

[kenmyfam]

Re: engine feeling like missing under load of plane

How hard is rebuilding carbs or do you just buy new? or is this best left to the mechanic?

Carb's are pretty easy. That is if you have an OEM manual to assist. You will get all the help you need out here if you do not understand anything in the manual.

 

[bartdjunkman]

Re: engine feeling like missing under load of plane

thanks for all the help. I may be asking more questions as i get into it but that will get me started.

 

[kenmyfam]

Re: engine feeling like missing under load of plane

Good Luck and fire away with any questions.