Powerhead Rebuild

Swampmouse

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Feb 2, 2007
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My other thread was inaptly named as now I have identified the problem and am 1/2 way through my rebuild (See mottor bogging down thread).

I have a '83 Johnson 115p I am rebuilding - 2 of my 4 cylinders are being overbored to .030. So here's the list of what I will order probably tomorrow. Please tell me if I am leaving anything off:

2 X .030 piston kits
2 X "regular" sized ring sets (I'm replacing the rings on the other 2 pistons as well)
thermostat
Gasket set (with all of the powerhead gaskets, exhaust, bypass, etc.)

I was not planning on messing with the camshaft seals/bearings as they seem to be ok. Also, I am not planning on replacing the cages and needle bearings - I didn't see any flat spots or abrasions on them.

Any advice - anything I am leaving out??

Any help appreciated.

Thanks,
SM
 

iwombat

Captain
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Jul 12, 2006
Messages
3,767
Re: Powerhead Rebuild

Since you'll be removing the rods, it probably wouldn't be a bad idea to new get big-end rod bearings as well. They may look okay, but they'll look that way until they're totally toast.
 

iwombat

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Re: Powerhead Rebuild

I guess I should clarify that a bit. The only way to really check those bearings is to mic 'em and see if they're still in spec. With normal wear you won't see anything abnormal. If they do have noticeable abrasions or flat spots it's probably time for a new crank as well as new bearings.

If I'm removing the rods on any engine I'll replace the big-end bearings/bushings w/o even thinking about it. (Unless they want $120/set for replacements. Sure, it's funny now!)
 

Swampmouse

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Re: Powerhead Rebuild

IS that the wrist pin bearings or the split cage (& needle) you are referring to?
 

iwombat

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Re: Powerhead Rebuild

In automotive parlance:

crank bearings = big end
wrist-pin = small end

Not sure if the marine folks use those terms or not.
 

Swampmouse

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Re: Powerhead Rebuild

Yeah, I noticed that when I took them out - sorry should have pointed that out. I found a kit with all the little extras for them (springs, etc) it's only a few dollars more than ordering 2 thermostats so i will just get it.

Any suggested parts places on line? This site doesn't have the pistons or rings I need.

Thanks!
 

tschamp20

Petty Officer 1st Class
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May 10, 2006
Messages
317
Re: Powerhead Rebuild

ishopmarine.com
anti-sieze
gasket seal
gallon of tcw3
tap and die set
beer!!!!
 

Swampmouse

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Feb 2, 2007
Messages
121
Re: Powerhead Rebuild

I didn't think of the tap & die - that could come in very handy!

Is the gasket seal the same as used on cars?

What anti-seize?
 

tschamp20

Petty Officer 1st Class
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May 10, 2006
Messages
317
Re: Powerhead Rebuild

yes as far as i know. the anti-sieze is usually used on spark plugs to keep them from getting stuck.but should also be used on stainless bolts that are threaded into aluminum.on my motor almost all bolts were 1/4-20 or 5/16-18 if you cant afford a whole set. if you can northern tool and equipment has a great set. about 35-40 bucks
 

mikesea

Lieutenant Commander
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Oct 1, 2006
Messages
1,830
Re: Powerhead Rebuild

you need the crankcase gel seal ,I would advise changing bearings too.I would change them all,and definatly the lower crank bearing.be sure you change the bottom main seal also on the crank
 

iwombat

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Re: Powerhead Rebuild

I was assuming you were doing this with the powerhead still attached, then I went back and read that you were getting the block bored. Wouldn't that be a nifty trick? Anyway, if the extra parts are cheap I'd be doing the whole ball of wax like mikesea suggested. You're right there anyway. The real cost is usually just the time.
 

Dhadley

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Feb 4, 2001
Messages
16,978
Re: Powerhead Rebuild

A couple of things come to mind --

I was not planning on messing with the camshaft seals/bearings as they seem to be ok.[/quote]

When talking to your parts guy don't refer to a camshaft. An 83 115 doesn't have one. Some parts guys are very easily confused.

When you get the block to a marine machine shop, not an automotive one, have them measure the bores. It'd be very unusual for a 20+ year old crossflow to still be within standard spec after honing.

Are you sure it has to be bored to .030? .020 won't clean it up?
 

iwombat

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Re: Powerhead Rebuild

"It'd be very unusual for a 20+ year old crossflow to still be within standard spec after honing. "

I was kind of wondering about that. I'm staring a re-ring in the face in the next year or two, and was wondering if I should be counting on a bore job as well.
 

Swampmouse

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Re: Powerhead Rebuild

The machinist looked at it and said to get a couple .030 pistons. The cylinders were scarred pretty good - the bottom starboard piston totally lost a ring.

This afternoon I looked at the 2 remaining "good" pistons and think I will replace them too. I have to get the rings anyway, so I think I will make the investment an go ahead and replace the other 2 with original size
 

Swampmouse

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Re: Powerhead Rebuild

But, maybe I should point out that the two "good" cylinders pushed about 125 each on the compression test
 

Dhadley

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Feb 4, 2001
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16,978
Re: Powerhead Rebuild

OK, the damage was most likely from coking caused by lugging it. I'd bet almost anything the port cylinders are going to be out of spec. No matter how good they "look". There's been some pretty high combustion temps going of for a while. I'd also bet the port pistons have collased skirts. They all move some but I'd bet those are really loose. Lots of clacking at idle most likely.

I wouldn't be surprised if .020 would clean up the starboard side. It's common for a machinist to want to go right to .030. Saves him time if .020 doesn't clean it up. Bores in one pass rather than two.
 
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