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OUTBOARD gooroo's

Big Red

Big Red

Well-known member
I am looking at a pontoon with a 1989 Merc. 90 horse on it. What seems wrong to me is the exhaust seems to blow from the back side of the engine towards the boat and not out of the prop. I did not ask the owner why it did that I wanted to here from others first.

And what should the compression be within reason
 
Which one of these pontoon boats will be BigRed's new boat??????
 

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Big Red said:
I am looking at a pontoon with a 1989 Merc. 90 horse on it. What seems wrong to me is the exhaust seems to blow from the back side of the engine towards the boat and not out of the prop. I did not ask the owner why it did that I wanted to here from others first.

And what should the compression be within reason
Click to expand...

From the backside towards the boat? don't you mean fromt the backside away from the boat?
there is some exhaust relieif just under the cowling that will blow behind the motor, if you watch it water should also come out of there as well. the exhuast will primarily come from out the prop but some will come from up top as well.
compression should be somewhere between 100-120psi per hole, most important is that all the holes are within 10% of each other.
 
cant see a 90hp on the one on the left.....thatd be a hairy ride for sure!!

BR, guru i am not, but i still cannot picture why the exhaust would appear to be in front of the motor....compression equal all cylinders for sure +/- 10%, i couldnt even guess what the comp should be!
 
The exhaust sound and bubbles seem to be coming out the back of the engine and hitting the back of the boat.


 
I have seen where guy's will drill holes in that area right above the cavitation plate to make it sound louder, usually two 3/4" or 1" holes on each side, that's the only thing I could think it would be, not sure why anyone would want it to sound loud on a pontoon boat though, one of my 200's have them drilled in it and I plugged the holes with a threaded plug because it was annoying to listen to in the midrange, sounded cool at WOT but that's about it.
 
Seal bad?

Or is the exhaust seal between the mid section and lower missing or bad and exhaust coming out the water intake? This sounds pheasable to me...
 
Maybe drilled the engine is a 89 and the pontoon is a 96. Its not the orginal engine.

Okay guys thanks for the help still open to any idea,s
 
just a thought, but does it have one of those happy trollers on it? maybe it is in the down postion making it look like exhaust is coming out the front...some people put em on toons to slow the idle speed down.

http://www.basspro.com/webapp/wcs/s..._16089_225011000_225000000_225011000_225-11-0


there isn't really much of a seal between the midsection and lower to blow out. exhaust would come out there if the lower wasn't bolted up all the way but i would doubt that is the case.
 
Okay I am not familiar with that model outboard. I know my 79 tower of power has a thick ~1 inch rubber gasket between mid and lower
 
Went back this evening to take another look and check compression. I was getting between 139 and 141 :confused:

Okay I found out the deal on the exhaust mystery. The engine was originally a 20" shaft he put a 5" spacer in, to make it a 25'' shaft. He says that he did not put a gasket their or something. The exhaust is leaking out by what looks to be 2 big studs with nuts on them. Maybe 1/2 studs

See pic for the area I am talking about . And does anybody know what shaft should be on a pontoon 20 or 25. Is this spacer some kind of butcher job or are they fine to use on a low performance pontoon.

By the way the boat is in the water so it makes things harder

 
i personally would stear away form a mota that someone made a 25 outa a 20:irked: but thats just me:p
 
You can buy a spacer to make just about any 20" Merc a 25". If it was purchased aftermarket from a firm that does this for a living, I would trust it. Center Console fishermen do it all the time when they are replacing a motor and can't find a 25" mid.

If it was "homemade", I agree with Ross.

From one sweet Checkmate to a Pontoon....my how things change.:D

Good luck Red.:thumb:

HD
 
if its a 6 cyl, its not an 89. they stopped making those in 86...an 89 would be a 3 cyl. a pontoon would use a 25", merc makes a kit to convert a 20 to 25.
 
The boat is a good deal with a mint trailer plus I can have a slip at the lake in a quiet cove for 150 bucks a year. Price so far is 5500.00 with trailer, the engine has around 80 hours since rebuild. And 80 hours on all new floor and seats, steering and shift cables.
 
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