1985 90hp mercury loss of power

[rjsizemore]

I have a 90 mercury just dont have the power to get out the hole that it use to have. Have good spark on all cylinders compression is 135-140 on all 6 cylinders. This motor has never had a rebuild its all orginal except I put a staor trigger and new switch boxs. This engine is on a 15.8 fiberglass fishing boat it has a13x21p prop it has had this size prop since new. I dont have a tach so dont know how many rpms I am turning but it seems to run as fast as it always did before just loss of power coming out of the hole. Would a rebuild help me? What kind of price range am I looking at.

 

[rjsizemore]

Re: 1985 90hp mercury loss of power

Should I just buy a new engine or fix my old one.

 

[Chris1956]

Re: 1985 90hp mercury loss of power

RJ, If you have the compression you cited in your post, there is no fundamental reason for the lack of power. I recommend you determine if a cylinder or two are fouling at idle and clearing out at high speed. I had this happen to me once, due to a leaky fuel pump diagram. While idleing, the bottom two cylinders would "load up", and not fire until I had gotton on plane.

 

[rjsizemore]

Re: 1985 90hp mercury loss of power

I forgot tp list I have installed a eletric fuel pump 4psi witch helped a little I just dont understand this motor.

 

[rjsizemore]

Re: 1985 90hp mercury loss of power

would my reeds have anything to do with my problem.

 

[rjsizemore]

Re: 1985 90hp mercury loss of power

What kind of job would it be to change the reeds

 

[ronmold]

Re: 1985 90hp mercury loss of power

reeds are not that hard but with compression as high as you state it is likly the hours on your motor are quite low and reeds should be in good condition. Bad reeds will have blowback that you can feel by putting your hand in front of the carbs when cranking it over. Have you done a de-carbonizing on it yet? Run a couple of cans of Sea-Foam through it.

 

[jimmbo]

Re: 1985 90hp mercury loss of power

Replacing the reeds on an inline 6 is a major job and requires complete disassembly of the powerhead.