1969 7.5 Merc cooling/exhaust issue

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Prof. Hess

Recruit
Joined
Jan 8, 2012
Messages
5
Greetings All,

I just got a new to me motor. And have reached a problem that has me stumped. The motor will not pee unless in gear and the rpm's up. It also seems at the lower rpm to put exhaust out of the pee hole. Is this a water pump issue or exhaust issue? How can I test this? I have already replaced the water jacket gasket, power head gasket, and exhaust gaskets. Not to say I did not make a mistake. I have a 9.8 parts motor I have robbed a water jacket and the exhaust plate and cover off of. This one has me screaming Uncle. Any helpful ideas? Thanks in advance.

Cheers Hess
 
I

impatico

Petty Officer 2nd Class
Joined
May 24, 2010
Messages
184
Re: 1969 7.5 Merc cooling/exhaust issue

impeller change? mine did the same and I took it apart the old impeller looked fine but changed anyway and good to go now
 
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Prof. Hess

Recruit
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Jan 8, 2012
Messages
5
Re: 1969 7.5 Merc cooling/exhaust issue

Yes, I did put in a new impeller. That is how I discovered the water jacket leak around the top spark plug. If it is worth mentioning the motor had some corrosion issues. Hence the use of exhaust plate and cover, and water jacket off the parts outboard.

cheers Hess
 
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Prof. Hess

Recruit
Joined
Jan 8, 2012
Messages
5
Re: 1969 7.5 Merc cooling/exhaust issue

I tore the motor back down again and found a great deal of the sludge that was described in another post that indicates an exhaust leak. I had put new gaskets in it. Is there something I am missing in getting this to seal right?
 
I

impatico

Petty Officer 2nd Class
Joined
May 24, 2010
Messages
184
Re: 1969 7.5 Merc cooling/exhaust issue

check both sides of the mating surface for gouges?? honestly I have never done any marine exhaust so just a thought lol
 
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Prof. Hess

Recruit
Joined
Jan 8, 2012
Messages
5
Re: 1969 7.5 Merc cooling/exhaust issue

I have made a new baffle plate and gaskets, also tracked down some Permatex #3. The motor was reassembled yesterday and will be barrel testing this evening. The baffle plate was pitted and very slightly warped. The replacement I made was thicker than original. I did the exhaust work as per this thread http://forums.iboats.com/showthread.php?t=438807 While trying to re hub my spare I discovered that some one in the last 40 or so years put the wrong lower unit on it. The lower unit has a six spline prop shaft.

Cheers Hess
 
Last edited:
P

Prof. Hess

Recruit
Joined
Jan 8, 2012
Messages
5
Re: 1969 7.5 Merc cooling/exhaust issue

I have done all this work and still an exhaust leak Whiskey Tango Foxtrot. What do I do now?
 
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