I have a 87 25hp Mariner that is driving me crazy! Please help!

benjo

Recruit
Joined
May 20, 2011
Messages
3
Alright here's the deal (what it does in order), starts great, runs great, it pisses (but somewhat weakly), water stream is intermintent, once engine is warm its will actually start to shoot steam out. Shaft starts to get warm-hothot. If I keep it WOT it will slowly lose rpm (over about a mile distance) till it cuts out. Wont start again. Let it cool off, starts right back up. I can troll with it all day, but it intermintently pisses and shoots steam after a while, I can run down the lake at WOT, back off to about half and it will start to **** again (sometimes intermintently and sometimes not), once the engine is cool enough I can take her to WOT again...
What I've done:
-Blew out lines (no change)
-Replaced impeller, the housing, and gaskets (no change)
-Replaced t-stat (no change)
-Replaced Head Gasket (no change)
If I run it with muffs on it seems to **** fine, even when I turn up the rpms. Water comes out of the hub just fine... I am at a loss, don't know what to do next. Seen some threads on exaust manifold gasket leaking and poppet valve causing similar symptomes. Please help! Thanks Joe
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
18,196
Re: I have a 87 25hp Mariner that is driving me crazy! Please help!

Don't know about the overheat but the stalling could be a clogged vent line.
Serial# mod#?? Profile? Salt/fresh water?
Is the overheat alarm going off?J
 

benjo

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Joined
May 20, 2011
Messages
3
Re: I have a 87 25hp Mariner that is driving me crazy! Please help!

Don't know about the overheat but the stalling could be a clogged vent line.
Serial# mod#?? Profile? Salt/fresh water?
Is the overheat alarm going off?J

Its a 87 Mariner 25hp Short Shaft
Model 25M 695
Fresh Water Only
Serial S 009738
There is no overheat alarm
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,938
Re: I have a 87 25hp Mariner that is driving me crazy! Please help!

This is the Yamaha branded as a Mariner. These are known for the inner exhaust plate problems and water tube problems..
 

benjo

Recruit
Joined
May 20, 2011
Messages
3
Re: I have a 87 25hp Mariner that is driving me crazy! Please help!

This is the Yamaha branded as a Mariner. These are known for the inner exhaust plate problems and water tube problems..
How would I go about fixing an inner exhaust plate problem and water tube problem
 
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