1990 mercury 15hp 2 stroke lacking power

1990 mercury 15hp 2 stroke lacking power

  • Lacking power

    Votes: 1 100.0%

  • Hesitation when wot bogs out

    Votes: 0 0.0%
  • Total voters
    1
  • Poll closed .
C

Corona kid

Cadet
Joined
Feb 11, 2012
Messages
9
Hey everyone,I just bought this motor and took it out,
Starts fine & idles fine.when I go WOT it seems like it is lacking
Power it also seems to bog, then when I slow down it wants
To die out. The motor is a 1990 mercury 15hp 2 stoke,
Please if any one can help I am very greatfull. What can I do
To troubleshoot and find out what the problem could be
Thanks everyone!!!!! Corona kid
 
jerryjerry05

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,927
Re: 1990 mercury 15hp 2 stroke lacking power

First step is a compression then a spark test.
Make sure both plug wires are on.My neighbor ran his 15 for months before I looked at it.
He said it ran great!!!I hooked up the other wire and he said it REALLY ran great!!!
Rebuild the fuel pump and make sure there is no water in the fuel.
Is the vent open on the tank?Last clean the carb.
Profile?Location?You might be close to someone who can help.J
 
C

Corona kid

Cadet
Joined
Feb 11, 2012
Messages
9
Re: 1990 mercury 15hp 2 stroke lacking power

Thanks jerryjerry05:) I did a compression check on both
Cylinders and both were 60psi cold engie with wot. From what I hear
This is low I would assume that this is the reason for the lack
Of power? What should the minumum psi be? Also when I took
Out the spark plugs the bottom one seemed to have a little bit brown
Substance on the bottom plug. I have a 6 gallon gas tank I don't see
A air vent it is a older metal can is this typical for older cans.
If any one can help I really need it. I am trying to eleminate
What I can before I send it to a marine shop. Oh and thanks
Agian jerryjerry05
 
P

phebus1

Petty Officer 3rd Class
Joined
Aug 19, 2011
Messages
85
Re: 1990 mercury 15hp 2 stroke lacking power

On any of the older metal 6gal tanks I have had, the caps are vented but there is no external vent that you see. Try running the motor on the hose with the cap off and see if makes a difference.
 
C

Corona kid

Cadet
Joined
Feb 11, 2012
Messages
9
Re: 1990 mercury 15hp 2 stroke lacking power

phebus1 said:
On any of the older metal 6gal tanks I have had, the caps are vented but there is no external vent that you see. Try running the motor on the hose with the cap off and see if makes a difference.
Click to expand...
Hey thanks phebus1! I'll try that, all I see on my gas can is
The cap with no vent and a gas gage that my fuel hose snaps
On to that's it
 
jerryjerry05

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,927
Re: 1990 mercury 15hp 2 stroke lacking power

The comp could be low because of the way you did it.
Both plugs out.Throttle advanced wide open.Install guage and pullllllll pulllllll pulllll.
When it stops going up then do the other cylinder.
The comp on a good guage should be over 100# My guage will read different than yours.
What your looking for is both cylinders about the same.
The older tank could be self venting.
Try running with the fill cap loosened a bit.
Brown on the plug?Change plugs.Post a pic of the plugs.J
 
C

Corona kid

Cadet
Joined
Feb 11, 2012
Messages
9
Re: 1990 mercury 15hp 2 stroke lacking power

Well when I did the comp check I still had one spark plug in
And I did have WOT.would 1 spark plug make that much of
A diferance & as for the gauge if borrowed it from autozone
And it was brand new but it went well over a hundred pounds
But the weirded thing is both of the cylinders read 60psi exact
Using WOT I assume it's the lever that opens the throat to the carb?
Can anyone explain how to post pics?
 
P

phebus1

Petty Officer 3rd Class
Joined
Aug 19, 2011
Messages
85
Re: 1990 mercury 15hp 2 stroke lacking power

You need both plugs out so the starter can spin the motor fast enough to get a true reading on compression.
 
C

Corona kid

Cadet
Joined
Feb 11, 2012
Messages
9
Re: 1990 mercury 15hp 2 stroke lacking power

Hi agian I did the comp test agian with both plugs out and got the same reading
60psi for both cylinders. What is weird is that both are the same exact reading,
Has anyone ever seen this? How much is it to fix to fix the compression problem
On a 1990 mercury 15hp outboard? I just want to say thanks to everyone that
Has giving me info about my issues with this outboard.
 
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