79 75hp Chrysler blown head gasket

57 7.5

Petty Officer 3rd Class
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May 25, 2007
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I have a 79 75 hp Chrysler model number 757H9E. I have been working on this motor and boat for a couple of weeks finally thought I had it ready to go and long story short the #1 & 2 cylinders had 0 compression. I read some threads on here and most all said check the head gasket and I did. It was blown between #1 & 2, last year the owner had a compression check and it was 150 on all three, had fuel pump rebuilt, carbs rebuilt, new fuel lines though out, impeller replaced and lower unit oil changed out. I've drained the fuel and emptied the carbs and refueled with fresh gas and oil mixture (50:1) and replaced the bulb (seemed like it was old and thought it as one symptoms I had early on). So I checked the pistons, they look fine, #3 has some carbon the other 2 look great. The cylinder walls look fine no damage there. Should I look for anything else before I put it back together? Is there anything i can do to #3 carbon without harming anything and what is causing it. I don't have a book yet, waiting for the mailman. Also is there a certain bolt pattern to follow when tightening and anyone know the torque specs for the bolts. They were all very easy to break loose. Do you have to put any sealant on the motor or gasket? Seems there were none when this was last done (paint on bolts was broken free or missing) so looks like someone has been in there before, maybe a rebuild or blown head gasket before.

Thanks for any help!
 
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Joined
Oct 22, 2007
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2,598
Re: 79 75hp Chrysler blown head gasket

Sell your Chrysler and get a 'Rude.

Either that or ask your question in the Force/Chrysler Outboard section where someone can probably help you out. :D
 

57 7.5

Petty Officer 3rd Class
Joined
May 25, 2007
Messages
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Re: 79 75hp Chrysler blown head gasket

Sorry I thought I was. I would prefer a rude for sure but it came with the boat and money is tight to be buying another motor. Thanks.
 
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phillnjack2

Ensign
Joined
Apr 30, 2011
Messages
918
Re: 79 75hp Chrysler blown head gasket

the bloke who said that chrysler had 150 psi compression is nuts, not a chance in the world.
just load up the piston area with a spray carbon cleaner.

hope you have luck with the chrysler folk.
just always remember a 75 chrysler is like a 45-50 rude, but they did look ok in their day.


phill
 

Frank Acampora

Supreme Mariner
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Jan 19, 2007
Messages
12,004
Re: 79 75hp Chrysler blown head gasket

Hmmm-- I guess those rude 'Rude guys have transferred your post to the correct forum.

Head bolts are tightened to 225 inch pounds or 18 3/4 foot pounds if you do not have an inch pound torque wrench. Tighten in a spiral pattern working from the center two bolts outward. Tighten in to or three steps until max torque is reached. After running the engine for about 1 hour or so, re torque all the head bolts. Gasket is installed dry.

Don't know what the compression remark was about, but factory new would be around 135-145. Depending upon the gauge used, the previous owner may have gotten a reading of 150 which would indicate a healthy engine internally.

DONT bother decarbing unless the engine has problems. A decarb treatment CAN lead to piston damage on these engines.
 
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57 7.5

Petty Officer 3rd Class
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May 25, 2007
Messages
93
Re: 79 75hp Chrysler blown head gasket

thanks acampoa I appreciate all the comments good or "Rude". :joyous: I thought 150 was a little high and for all of them to be the same. I wonder if it's been rebuilt before and that's where the 150 came from. I'll get the carbon cleaner and I'll get a torque wrench tomorrow. Gasket should be here tomorrow or Tuesday. I've got everything cleaned up and smooth, ready for install. I also used compressed air to blow out any debris that may have gotten in their during the cleaning process, I put rags in the cylinders to keep stuff out used the air just in case. Hope she fires up and runs like a champ so I can get on the lake this weekend.
 

57 7.5

Petty Officer 3rd Class
Joined
May 25, 2007
Messages
93
Re: 79 75hp Chrysler blown head gasket

Just to let everyone know replaced the head gasket today and she is running. Took her out to the lake and she runs great, she dies at idle though. So i'm off to read threads on idol adjustments and fuel mixture.
 
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