Please help, Merc 115 4-stroke lost power

[Seapro1]

I have a 2005 Merc 115, 4-stroke. It appears to have no more than 100 hours of use when I bought it a year ago. Since then I have put about 30 hours on it. When I first got it the best it made was 35 mph at 5000 rpm. It gradually dropped down to 3000 rpm. Today, after I replaced oil, new lower gear lube, new water separator, new fuel filter, checked and cleaned spark plugs, it would hit 6000 rpm on land but once in water it would not go past 1200 rpm and coughed all the way. I put Sea Foam in the gas tank and that did not do anything.

My neighbor thinks that the idle limiting sensor has gone bad, which would not allow the rpm to go up. I looked up the manual and could not find that sensor he was talking about.

What should I look into? I just cannot believe having problem with an engine which hardly sees 200 hours of use. Thanks in advance for your advices.

Seapro1

 

[86RajunCajun]

Re: Please help, Merc 115 4-stroke lost power

Why are your revving to 6k rpm on land? Not safe to go that high for long without the engine being under load.

Go through everything you did in the fuel system and test the ignition system.

if you dont have a manual for the engine, get one, it will help a lot.

GL
RC

 

[Seapro1]

Re: Please help, Merc 115 4-stroke lost power

Someone told me to clean the carbs. I looked up my shop manual and could not find any description of carb. Does a 4-stroke EFI engine have carburetors?

 

[Steves69ss]

Re: Please help, Merc 115 4-stroke lost power

Seapro,...Im no boat expert ..but EFI stands for Electronic Fuel Injection.... so....no it does not have carbs....I also agree with the RajunCajun about not revving your engine high when its not under a load...just asking for problems..
I dont know anything about an idle limiting switch?..sounds like a fuel pressure problem to me..could also be caused by weak spark....

 

[Seapro1]

Re: Please help, Merc 115 4-stroke lost power

Steve,
Thanks. That's what I thought. The mechanic told me I needed a carb job, which is $600. I did not believe him. What a crook.

I filled the filter cup with Sea Foam today and run the engine. After four fills it seems to run much better. I have not put the boat in water to know if it really works or not.

I rev it up to 6K just to see if it would get there. It was only momentarily, not more than ten seconds.

 

[75TowerOfPower]

Re: Please help, Merc 115 4-stroke lost power

Has your mechanic seen this motors? and have you told him its a Merc 115 with EFI? If so don't take anything else to this guy. You don't have a carb and therefor the 600 bones would be pocketed by him.

 

[Seapro1]

Re: Please help, Merc 115 4-stroke lost power

No, he did not see the boat, but I did tell him it is a 4-stroke with EFI. This is one guy I have to stay away from. He also said he had to go in for a surgery and would not be able to work for the next two months, so, he recommended another mechanic, whom he said to be very experienced with Merc.

Just for the heck of it, I called up this guy and guess what....his phone number is a bait camp. Yes, a bait camp, he is a tree shade mechanic.

I called a Merc dealer today. The service manager was adamant that the problem is with dirty fuel plugging up the injectors. He said his company has proprietary equipment and chemcal to clean out the injectors without having to replace or taking it apart. It costs $300 for the cleaning.

Ok, that sounds fine, but then he went on to say that if the cleaning did not fix the problem then they will try something else with additional charge.

UH...to me that means they do not know what they are doing !! capable mechanic should be able to diagnose and find the problem before doing repair work instead of this in-the-blind trial and error approach at the expense of customer. Seems to me that is a $300 bonus for them.