The REAL cost of partly-rebuilding an older engine (Johnson 85 1979)

[mz3bo]

Hello Friends,

As you saw in my previous post, my 1979 Johnson 85 is having 1 piston with low compression (90 - 120 -120 - 120) but is still running Strong ! I have read a many site about it's not worth rebuilding it because of cost etc.. some even approached a 2500-4000$ estimate cost to fully rebuild the motor.

My question is, as a DIYer, what can be the real, not exagerting cost of PARTLY- rebuilding such engine, especially for my personnal case. This is what I came with by looking at the parts diagram. Of course, I will be doing this myself

To my understanding, these parts has to be changed and cannot be reused:

1- 4 pistons with ring and wristpin and all clips (wiseco are $56 per kit per piston)
2- 4x rebore if necessary (not sure yet it will be necessary, maybe just rehone)
3- 4x wrist pin bearing
4- All gasket exposed while opening up the engine
5- few oring here and there and seals....

These parts, to my understanding, can be reused:

1- 4 Connecting rods
2- crankcase head bearing assemble
3- Nuts, bolts and washer that are not damaged
4- Crank ! (should be good)

Considering I have done all this so far during the last months:

1- Carbs rebuild
2- new starter
3- New CD2
4- New coils pack
5- New fuel pump
6- New plugs
7- New thermostat
8- New waterpump
9- new stator power invertor (can't remember the real name)


What do you guys think. Am I missing something Really big that can overcome my little project ? Any help would be greatly appreciated !

Thanks
Bo

 

[Faztbullet]

I myself don't like the Seizeco pistons as they require extra clearance,need to go thru several heat cycles to temper piston and you have to allow engine to reach temp before WOT throttle operation but they do run OK in a worn hole. Go with a WSM piston as only $13 more and you will need a tube of gelseal and primer..Since your going to have to do block work just find a 140 block with pot belly and put the new pistons and you stuff in it. They you have a good 115hp motor.

 

[emdsapmgr]

My factory 1976 service 135 manual has a number of paragraphs of salvaging a piston or two for re-use in a block. Shows you how to clean out the ring grooves with an old broken ring with sharp edges. As long as the piston is round and you can clean the carbon off of the ring grooves and piston skirts, the factory used to say that any old piston could be reused. I know I've followed this advice during rebuilds on some older V4 engines. A number of them had used pistons and one new one. All of them ran fine for me. It's really your call. The factory does make a gasket set for the whole engine. May save a few bucks and save scrounging for them. The powerhead gasket set is listed on the exploded parts diagram called: cylinder and crankcase. While you have the engine open, you might consider adding 4 of the intake filler blocks. Only used in some older 115's and the 140's, the rubber blocks are discontinued, but readily found on ebay and marine salvage yards. The blocks are worth 3-5 hp on a V4. (322684)

 

[mz3bo]

My factory 1976 service 135 manual has a number of paragraphs of salvaging a piston or two for re-use in a block. Shows you how to clean out the ring grooves with an old broken ring with sharp edges. As long as the piston is round and you can clean the carbon off of the ring grooves and piston skirts, the factory used to say that any old piston could be reused. I know I've followed this advice during rebuilds on some older V4 engines. A number of them had used pistons and one new one. All of them ran fine for me. It's really your call. The factory does make a gasket set for the whole engine. May save a few bucks and save scrounging for them. The powerhead gasket set is listed on the exploded parts diagram called: cylinder and crankcase. While you have the engine open, you might consider adding 4 of the intake filler blocks. Only used in some older 115's and the 140's, the rubber blocks are discontinued, but readily found on ebay and marine salvage yards. The blocks are worth 3-5 hp on a V4. (322684)

Hi, thanks for answering. Do you think the estimate I have on the required parts listed above is very close to what I will need to spend in order to bring up this motor back to a healthy life ?

Thanks

 

[interalian]

I may be off a few dollars, but the boring for 4 holes to 0.030" over was about $550 Canadian, and the parts about $1100 Canadian - labour was $0 Canadian.

I did all 4 pistons new (OE ones come with wrist pins, clips and rings - there are no wrist pin bearings). I re-used crank, rods, needle bearings as all were perfect. I could have just rebuilt the 90, but I found a junk 140 that was 3 years older but compatible era and used its block and accessories as the basis of a big power upgrade. Link below in my sig line.

 

[emdsapmgr]

If you re-use three pistons, that means you only need one new one. Depends on the cyl liner for that damaged piston. You may be able to get by with honing it, or you may need to overbore and use an oversize factory piston. Re-use the other 3 pistons. You will need 4 new ringsets. Most factory oversize pistons come with new rings. Standard do not. You will need to hone the 3 standard cyl liners, maybe #4 too, if you go standard size. Rest of your list looks good. I agree with interalian, on the reuse of crank, rods, needle bearings and rod bolts.

 

[Faztbullet]

You do not want to reuse them high ring pistons as it will result in what you have now. From the pic's you posted a previous owner did this on #3 and look where your at .

 

[gm280]

If you are doing all the non-machine shop type work yourself, I certainly don't see a $2500 or above rebuild myself. You can do it for a lot less. Even with buying new pistons and rings, it wouldn't come close to those suggested prices. JMHO

 

[bob johnson]

you guys replace the rods on motors with weak compression??? seems over kill...... I am all in for getting as much done when the motor is apart... like if you are tearing it down to bore one hole...JUST bore them all and start all new with nice round holes and a good fit in all cylinders!!!!...but I would just put a working power pack and coils , right back on, same goes for the starter, and rectifier, and fuel pump.....if it was working when it came off, it should be good to go....I am all for new o rings and gaskets !!!bob

 

[emdsapmgr]

fastbullet has a good point. Back in the years of your engine, OMC used pistons with the ringsets right at the top of the piston. These made high compression, but were very prone to failures after a few years. I'm not so sure the rings were any different than today, but the pistons were. So, based on the possibility that you may have an engine with all high-ring pistons, I'd recommend throwing all of them out and using 4 new (low ring) pistons.

 

[bob johnson]

fastbullet has a good point. Back in the years of your engine, OMC used pistons with the ringsets right at the top of the piston. These made high compression, but were very prone to failures after a few years. I'm not so sure the rings were any different than today, but the pistons were. So, based on the possibility that you may have an engine with all high-ring pistons, I'd recommend throwing all of them out and using 4 new (low ring) pistons.

well hed have to go get a different block like fazt mentioned.....I am assuming all the other 85 hp parts will bolt up to a 140 HP block.....

 

[jakedaawg]

Just for your thoughts.....I have several block laying around that are in a similar state to yours. Have not found buyers yet so I have not rebuilt one yet. I recently needed any variety of v4 for a work barge. Before putting one to gether I did a quick search. Found a 60* looper 115 running for $400. Told the guy I'd give 450 if he would wait two hours while I drove there. I now have one of the quickest work barges I have seen.

Moral=deals are out there.

 

[mlaajanen]

Well if you like to rebuild which is a pretty fun job IMHO why not focus on the workmanship and by a complete rebuild kit with all that is needed?

I think kits like this should be pretty nice to use or do others have second opinion?

http://www.maxrules.com/fixphead_omc.html or similar.