Welcome to the DoItYourself Forums!

To post questions, help other DIYers and reduce advertising (like the one on your left), join our DIY community. It's free!

Acceleration problem


rbgraber's Avatar
Member

Join Date: Aug 2006
Posts: 18
AR

06-29-10, 09:04 AM   #1  
Acceleration problem

90 HP Force Outboard. I run this engine every weekend. Starts Just fine, runs good. When I accelerate 0-30% no problem 31-60% will stall, but if I quickly accelerate to 61% or more runs fine again. Any thoughts?

Blair

 
Sponsored Links
samuari's Avatar
Member

Join Date: Jul 2008
Posts: 541
MN

06-29-10, 06:30 PM   #2  
That's a little odd problem.

I guess I would start with the basics. Spark plugs, fresh fuel, compression test, check timing.

 
rbgraber's Avatar
Member

Join Date: Aug 2006
Posts: 18
AR

07-15-10, 12:09 PM   #3  
I have put new plugs in it and fresh fuel. Still same issue.

 
samuari's Avatar
Member

Join Date: Jul 2008
Posts: 541
MN

07-15-10, 06:07 PM   #4  
Try to get someone to pump the primer bulb while it's acting up. This will eliminate the fuel pump.

How did the spark plugs look? Where they all even colored?

 
rbgraber's Avatar
Member

Join Date: Aug 2006
Posts: 18
AR

07-18-10, 02:02 PM   #5  
top 2 plugs were black not horrible, bottom plug was silver/brown

 
samuari's Avatar
Member

Join Date: Jul 2008
Posts: 541
MN

07-20-10, 07:42 PM   #6  
I would get a compression test done just to be sure you're dealing with a mechanically sound engine.

Does the problem show up as you're getting on plane?
What happens if you're on plane, back off the throttle to the problem spot and then accelerate?

It sounds like a fuel or compression problem.

 
rbgraber's Avatar
Member

Join Date: Aug 2006
Posts: 18
AR

07-21-10, 12:53 PM   #7  
I will try having someone pump the bulb while accelerating. I will also try backing off and accelerating again.

Let you know.

Thanks for the feed back.

BG

 
rbgraber's Avatar
Member

Join Date: Aug 2006
Posts: 18
AR

07-25-10, 06:55 AM   #8  
Pumping the bulb while accelerating did not help.

Backing off while on plane & then accelerating again is does not act up.

Now THE ISSUE, I did a compression test:

Top 90, Middle 120, Bottom 40

I know that is not good, they should all be close.

 
samuari's Avatar
Member

Join Date: Jul 2008
Posts: 541
MN

07-25-10, 03:21 PM   #9  
Your motor needs to be rebuilt, or replaced. For that low of compression there is going to be significant scoring of the cylinder walls on the low cyl.

The problem you are going to run into is parts availability. Many parts are no longer available for the force line through mercury. I personally would suggest replacing it with a newer model. I have a couple late 80's mercury motors that I run on my drag boat and I found mercury no longer sells head gaskets. I have found another source but it goes to show a very common part that they quit making.

 
rbgraber's Avatar
Member

Join Date: Aug 2006
Posts: 18
AR

07-26-10, 09:04 AM   #10  
Thanks for all your help.

I am considering a Honda or Yamaha 4 stroke, any advice?

 
samuari's Avatar
Member

Join Date: Jul 2008
Posts: 541
MN

07-26-10, 08:17 PM   #11  
You can't go wrong with ether manufacturer, if you are buying new I would chose what dealership is closer and or better service. I'm not suggesting you will have any problems but if you do you don't want to drive 2 hours for service.

Good luck.

 
Search this Thread