40 hp Evinrude - no power

[Olde Merc]

A friend of mine has a 40 hp Evinrude, probably about a 1993 model (it's a twin with twin carbs). When the boat came out of storage this spring, it hasn't been running right. At full throttle, it seems to only make 40% of it's power. The engine also revs very low for full throttle, the RPM's are probably well under 4000 RPM (just a guess, there's no Tach). The engine runs smooth and sounds normal otherwise, it's just seems like the throttle is limited. In neutral, the engine revs freely and will reach high RPM's no problem.

We checked the throttle linkage, other than there being lots of free play initially, it opens both carbs all the way. We also ran a can of carb cleaner through the carbs.

Any ideas on what we can check before we bring the boat in for service?

Thanks.

 

[Rick.]

Re: 40 hp Evinrude - no power

Sounds to me like it's only getting spark on one cylinder. I would check for spark first. Best of luck. Rick.

 

[tashasdaddy]

Re: 40 hp Evinrude - no power

compression, spark, carbs. only way to clean carbs is disassemble them. besure to remove and clean all jets.

 

[Silvertip]

Re: 40 hp Evinrude - no power

Spraying stuff into the carb throats doesn't clean anything because it can't get INSIDE the carb. It needs to be added to the fuel to get inside and that is generally a waste as well. Check for spark. An engine running on half its cylinders will rev freely in neutral so that is not a valid test.

 

[Olde Merc]

Re: 40 hp Evinrude - no power

If it were only running on one cylinder, would it not be very rough running? It runs very smoothly. Although I did notice that when it was running and I sprayed carb cleaner in the top carb, the engine wanted to stall it (as it should), but the bottom carb nothing seemed to happen when it was sprayed. It looks like each cylinder has it's own independant carb.

I realize that the only way to truly clean a carb is to pull it apart and soak it in carb cleaner. The carb cleaner was used to clean up the throttle linkage and any varnish around the throttle butterfly. We had a can, so we tried it (it can't hurt).

I should note the the engine ran fine in the fall when put away. This just started in the spring when it was taken out of storage. This is also a low use, low hours engine.

 

[Rudi2]

Re: 40 hp Evinrude - no power

Although I did notice that when it was running and I sprayed carb cleaner in the top carb, the engine wanted to stall it (as it should), but the bottom carb nothing seemed to happen when it was sprayed.

Well, sounds like a good place to start,

As the man said, spark, compression, fuel

 

[Rick.]

Re: 40 hp Evinrude - no power

My experience is based on OMC's 15 hp and smaller although I just acquired a 40 HP this weekend. For the motors I am familiar with it is almost impossible to tell they are running on one cylinder. They run smooth as silk to the ear. What you notice is a real lack of power when connected to your boat and, if in a barrel, more unspent fuel than normal. Rick.