1978 Chrysler 85HP Powerhead Swap

topgun3690

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Did compression/spark tests today.....150 across the board and good spark on all three. Had some minor fuel leaks at the carbs....snugged up the mounting nuts and fuel bowl bolts.....another 30 min run on the muffs and it seems fine now. Next run will be on the lake. Do you typically see higher comp numbers after the PH is broken in properly? This test was done with just 1.5 hours run time, got a ways to go yet. 150 not bad but thought it would be higher?
 

Nordin

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I have checked in my workshop manuals Clymer and Seloc (do not have OEM manuals for this engine) and Clymer says 145-155 PSI, Seloc says 150-165 PSI.
I think yours 150 PSI will stay there, maybe rise some PSI after break in.
But 150 PSI is definitely in spec and good after a rebuilt power head.
I have some 70 and 75 Hp engines with rebored power heads but they are only partly rebuilt.
Have bored one or two cylinders, no one with all three and I have not checked the compression after break in.
Have checked the rebored cylinders after i have reassembled it and if I do not remember wrong the compression has been 150-155 PSI.
Good luck with your "new" 85Hp Chrysler, it will last for a long time now if you maintain it well and not run the hell out of it.
 

Nordin

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Just have to add.
The OEM workshop manual for Force 85Hp through 1988 year model calls for 135-155 PSI.
The 85 Hp Force are the same power head as the 85Hp Chrysler in bore and stroke, so I think the compression will be in the same range.
 

topgun3690

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Thanks Nordin.....This rebuilt PH I got from Franz is actually from a 1986 Force(dark blue). All cylinders bored .020 with Wiseco pistons. He put a different bearing cage on it for the distributor belt and drilled/tapped for the distributor mounting bolts. With the blue body and lots of white parts you can definitely tell it is not original.
My Chrysler manual says 145-165 for the original PH....your workshop manual says 135-155 for Force 85Hp thru 1988...which is what I have now.....so that 150 psi looks better. Will check it again after the break-in to see if it goes up any.
I will maintain it well and try not to run the hell out of it! :ROFLMAO:
 
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jerryjerry05

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IF??? the block is originally painted blue then it's not a 86
Blue blocks started in 87, maybe he painted it??
Look on the block under the ignition panel, there should be a foundry stamp
with the year in the center also on the bottom of the intake manifold under the bottom hole is another foundry stamp.
In the year 1987 they made changes in the block, the biggest was they redesigned the exhaust chest cover and they take 2 different gasket sets.
 

topgun3690

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IF??? the block is originally painted blue then it's not a 86
Blue blocks started in 87, maybe he painted it??
Look on the block under the ignition panel, there should be a foundry stamp
with the year in the center also on the bottom of the intake manifold under the bottom hole is another foundry stamp.
In the year 1987 they made changes in the block, the biggest was they redesigned the exhaust chest cover and they take 2 different gasket sets.
Thought he said it was an '86....maybe I misunderstood what he said. Will try to find those foundry stamps and find out what it is. Going by the parts diagrams on marineengine.com it shows the newer style thermoswitch started in 1986....which it has.....so I may be off by a few years. It's also possible he used parts from different year models when he rebuilt it.....kind of a "franken-force" powerhead....who knows. And I believe the exhaust chest cover is the same as my old one, so.....I'm confused. Lol.
 
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racerone

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Putting oil on the flywheel and crank tapers is a mistake / blunder !-----They are to be assembled clean and dry.
 

racerone

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Yes , I read that you did.-----However someone else suggested oil on these tapers !
 

topgun3690

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"Look on the block under the ignition panel" Are you talking about behind the CD box or distributor? Will be back at the shop on Wednesday and will have a look. The Force Blue paint doesn't look new......doubt if Franz painted it, but maybe somebody else did at some point. IF?? he did build this PH using spare parts he had on hand (am sure he has a warehouse full) I don't think it really matters, as long as it was assembled correctly with good parts. Kind of like the ole Johnny Cash song about building a Cadillac "One Piece at a Time"....lol
 
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topgun3690

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Mr. jerry you are correct.....it's not an '86.....it's a 1988 Force powerhead.....the pic couldn't be clearer.....thanks.
 

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topgun3690

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Update......just about finished with the break-in on this rebuilt PH, ran it for 4 hours yesterday. Was running real good, then during the last 30 minutes it sounded different, like it was struggling to maintain rpm, and noticed a vibration. My first thought was the lower unit. Raised the motor and noticed the black plastic prop nut was gone.....but no obvious damage or anything caught in the prop. Limped back to the ramp and headed home.
Had just replaced the gear lube before the PH work, so it only had a few hours on it. When I drained it after I got it back home, it was black and filled with tiny metallic shavings....so many particles that it made the lube thicker. No signs of water intrusion though. Took a pic but all it showed was a reflection off the oil.
The acronym B.O.A.T. came to mind.....because 1K is about what it will cost for a rebuilt unit. :cry:
 
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The Force power

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Update......just about finished with the break-in on this rebuilt PH, ran it for 4 hours yesterday. Was running real good, then during the last 30 minutes it sounded different, like it was struggling to maintain rpm, and noticed a vibration. My first thought was the lower unit. Raised the motor and noticed the black plastic prop nut was gone.....but no obvious damage or anything caught in the prop. Limped back to the ramp and headed home.
Had just replaced the gear lube before the PH work, so it only had a few hours on it. When I drained it after I got it back home, it was black and filled with tiny metallic shavings....so many particles that it made the lube thicker. No signs of water intrusion though. Took a pic but all it showed was a reflection off the oil.
The acronym B.O.A.T. came to mind.....because 1K is about what it will cost for a rebuilt unit. :cry:
Ouch! had you torn the LU apart before? If not it may of been (hopefully) a residue???

I just re-read the whole adventure and nothing about a tear down of the LU so I suggest to change the oil and run it to see if it continues
 
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topgun3690

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Ouch! had you torn the LU apart before? If not it may of been (hopefully) a residue???

I just re-read the whole adventure and nothing about a tear down of the LU so I suggest to change the oil and run it to see if it continues
This LU has never been torn apart....original owner....just regular fluid changes. I wish it was just a residue, but unfortunately this thing was making some serious metal. And the way it was acting on the lake, think I was lucky to make it back to the ramp.
 

The Force power

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This LU has never been torn apart....original owner....just regular fluid changes. I wish it was just a residue, but unfortunately this thing was making some serious metal. And the way it was acting on the lake, think I was lucky to make it back to the ramp.
We too far from each other, I could helped you with parts for it/complete unit
 

topgun3690

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We too far from each other, I could helped you with parts for it/complete unit
Thanks.....appreciate the thought. Am in no hurry now that winter is here and the holidays are coming up. Do you know what year models would be compatible for LU swap? It is a one piece with single exhaust.
 
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