Motor Keeps Stalling

[Freddie2]

Hi, I have a similar problem with my 1997 Mercury 25hp. It has very low hours on it. It starts up and runs fine but after it gets hot about 20 minutes of driving, it doesn't go more that 5 miles an hour and will stall if I push the throttle to 3/4 position.
I originally thought it was a fuel problem and replaced the tank, lines and fuel filter but still have the same issue.
If I let the motor sit for 20 minutes and then drive it it will be fine until it gets hot again.

I changed my thinking that it may be electrical and changed the coil last week. Took it for a long ride last weekend and it did great for hours but then, after driving slow for 10 minutes it died when giving it 3/4 throttle. It doesn't start up easily after it dies

could it be a crank sensor? Computer?

Let it sit. Then drove back to the dock with no problem.

I'm now thinking that the fuel my be boiling in the engine case but I would think that everyone would have had to had this problem if this was the case.

Thinking of putting a small electric vent fan to suck the heat out of engine cover.

Someone must have a fix for this after seeing all these similar posts.

Please help.

Fred

 

[GA_Boater]

Freddie2 Welcome aboard.

This is your new thread. It's better to have a thread of your own than tagging onto an 8 year old dead thread.

You have to do some troubleshooting instead of throwing parts at it - All you've done is make a dent in your wallet with no improvement.

2 or 4 stroke? Carbed or fuel injected? Have you changed the impeller? It may be overheating.

 

[Freddie2]

Hi GA,
Thanks for the info. I couldn't figure out how to start a new post on this site. I am a car mechanic by trade but I must confess that this is my first outboard motor and my first boat for that matter. I replaced the coil because I could see hot spots on it and checked the resistance. It was slightly out of specs compared to the new one I installed.

It is a 4 stroke and it's carbureted. I have not changed the impeller but I've been watching the flow out the back and it seems fine. I cleaned the carb by running the motor on straight carb cleaner just because it was cheap and easy. I don't think it would be a carb problem since it runs great until it gets hot. In my experience carburetors don't usually act like this.

I'm going to revisit the impeller idea this weekend. That seems to make good sense.

Thanks for sharing.

Fred