15hp stalls when trying to accelerate

dave green

Recruit
Joined
Jun 3, 2009
Messages
2
Hi,
I have a 1974 - 1975 15 HP Evinrude. It will start and idle fine, you can even reach in and open up the throttle manually and it will increase in RPM's. However, when you shift it into gear and start to accelerate, it boggs right down and stalls. It will idle in gear, you just can not accelerate at all.
Any ideas / help would be appreciated.
Thanks,
Dave
 

bankerjohn

Chief Petty Officer
Joined
Mar 21, 2008
Messages
444
Re: 15hp stalls when trying to accelerate

I assume you've already checked the plugs?

Sounds like maybe one of the cylinders isn't firing properly ... start your motor, then pull one plug wire off ... if the motor dies, the other cylinder isn't firing properly. If there's little change in how the motor sounds, put the first wire back on ... and pull the other one off and see if the motor dies.

If that test reveals a bad cylinder ... then your problem could be as simple as a bad plug wire ... or it could be a bad coil.

If it's not the ignition system, then the next place I'd look is the carb ... high speed jet??!!
 

mmccoy555

Petty Officer 2nd Class
Joined
Jun 3, 2009
Messages
131
Re: 15hp stalls when trying to accelerate

It's more than likely the carb. Even crap that you can't see will clog em up. I would pull it apart completely and use carb cleaner and compressed air. It's probably a clogged jet. does it run under a load with the choke on?
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: 15hp stalls when trying to accelerate

also change all fuel lines to B1 rated alcohol resistant fuel lines. (ethanal eats old lines, and clogs carbs). read all of the TOP SECRET FILE.
 

dave green

Recruit
Joined
Jun 3, 2009
Messages
2
Re: 15hp stalls when trying to accelerate

Hi,
Thanks for the info.
Maybe I should have written more about what we have done.
My dad is a great mechanic (US Airforce, jets as well as prop jobs, GM Dealership and Tractor Trailer Diesel Tech) and has looked into this problem, but we are still kinda stumped.
We put in New Plugs and Fuel lines. He has taken off the fly wheel and checked both sets of points and everything under there (found a bad wire that flexes when the timing plate advances and fixed that too). Carb was taken off and cleaned. Fresh new gas the day before we put it in the water which was this past weekend. Fuel screen checked, fuel pump taken apart and inspected and put back together (there was a little gunk in there but cleaned up everything before reassembly)
I am going to look up how to check the coils, however it seemed like a fuel problem to us. Does anyone know how to check the fuel pump??? I am thinking of taking the carb back off again and going through it again.
I was hopping maybe someone had had a similar problem with their motor and could point me in the right direction. I know thats probably a long shot LOL.
Thanks again for all the help and if you have any further info / ideas please pass them along to me. Summers are short up here in Northern Maine and I would like to get it fixed before our week of Summer is up. LOL Thanks again. Dave
 

Rick.

Captain
Joined
Jul 30, 2006
Messages
3,740
Re: 15hp stalls when trying to accelerate

Sure sounds like a dirty carb. to me. Take another go at it and be very careful to clean every hole passage from both directions and follow up with a good shot of compressed air. Best of luck. Rick.
 
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