Attempting a motor rebuild

[Captndrydock]

out of 50 "clean" motors I see, i would say 47 of them need a bore job. especially if a cylinder is scored. just did a 70hp 1982 johnson that only had 6-8/10ths of wear, havent seen one that good in ages. but cannot recommend doing it right the 1st time enough. there is nothing like the feeling of confidence putting together a motor you know was done right. a bore and finish hone is $50 a hole at Jay's Block shop in Doyle, TN. hes one of the best outboard machinists in the country. don't mind paying for shipping. dont skimp on honing old cylinders in such a high performance motor like that especially is my advice

Apologies for the late reply, didn't get a notification. Thanks for the info!

 

[Mc Tool]

Re sleeve will get you back to the original size. It is a good idea when the cylinder has been oversized before and when over seizing does not make practical sense because the cylinder walls are badly scorched. At least here where I live there is not a great price difference between the two. I am not so sure that Chrysler parts are still available. It has been a while since mercury bought them out

Dunno about engine machining costs over there but I got a rude shock when I wanted my ( 2 cylinder )18hp tohatsu bored.......180 bucks per pot ......I bought a brand new block for $305.
Last time I resleeved a block it was a 70hp johnson and it needed honed and decked .

 

[cyclops222]

check prices the Me Tool way.

 

[Captndrydock]

Dunno about engine machining costs over there but I got a rude shock when I wanted my ( 2 cylinder )18hp tohatsu bored.......180 bucks per pot ......I bought a brand new block for $305.
Last time I resleeved a block it was a 70hp johnson and it needed honed and decked .

Well I've heard about 65 buck a pot. But I may not even need that. I pulled the head and there's no scoring on the cylinders or pistons, as far as I can tell. Hoping maybe just new rings.

 

[racerone]

New rings on old pistons may be a mistake.

 

[Captndrydock]

New rings on old pistons may be a mistake.

At first I thought you were referring to a wallowed out bore. But your saying new rings on old cylinders may cause issues...

What issues does using new rings on old pistons potentially cause?

The nice thing about not reboring and using original pistons is about $800, lol... And no loss, besides the 476 block, if I can't get this thing back together successfully. Then again, it'd be a fun project, so...

 

[Mc Tool]

Its likely that the ring grooves are worn. You said in your 1st post that the piston was loose and that the top ring was loose in its groove ......most of this wear will be on the piston. If the rings were tight in their grooves then you probly could re-ring the motor but if they are loose not only will they hammer up and down in their grooves as the piston changes direction but they can also twist and they will never seal properly. All of this will cause accelerated wear and loss of power. If the bores are not to bad you maybe able to fit new pistons and rings be OK , hell I even fitted good-ish used pistons ( new rings ) into an old 50hp rude once and that went ok.
Another consideration is that while you can look into a port and see rings you cant verify that they aint broken somewhere you cant see.
The fact that this pot is down on compression ( 125 aint that bad ) suggests there are issues .
You will have a much bigger smile on your face if this engine runs well as opposed to just goes sorta ok when you have finished the resto . If you have the time look around for parts , new or used ..... I dunno if you can get Chinese pistons for this engine but if you can Id go for that . I have fitted Chinese pistons into a few 2 strokes and are yet to be disappointed. Try Ebay for parts too .... you never know what will show up ( Loosely quotes Ric Harrison )
I just had a quick look and on ebay ( searched 1977 Chrysler 135hp outboard pistons )there are some there . There is a piston kit that suggests that the 40 to 150hp use the same piston kits ( probly 2 3 and 4 cylinder motors hence the same size piston )

 

[Captndrydock]

Its likely that the ring grooves are worn. You said in your 1st post that the piston was loose and that the top ring was loose in its groove ......most of this wear will be on the piston. If the rings were tight in their grooves then you probly could re-ring the motor but if they are loose not only will they hammer up and down in their grooves as the piston changes direction but they can also twist and they will never seal properly. All of this will cause accelerated wear and loss of power. If the bores are not to bad you maybe able to fit new pistons and rings be OK , hell I even fitted good-ish used pistons ( new rings ) into an old 50hp rude once and that went ok.
Another consideration is that while you can look into a port and see rings you cant verify that they aint broken somewhere you cant see.
The fact that this pot is down on compression ( 125 aint that bad ) suggests there are issues .
You will have a much bigger smile on your face if this engine runs well as opposed to just goes sorta ok when you have finished the resto . If you have the time look around for parts , new or used ..... I dunno if you can get Chinese pistons for this engine but if you can Id go for that . I have fitted Chinese pistons into a few 2 strokes and are yet to be disappointed. Try Ebay for parts too .... you never know what will show up ( Loosely quotes Ric Harrison )

Thanks for the detailed response MC! Yeah, that's exactly what I was thinking too. That ring landing had wallered out. Okay, I'm convinced and will adjust my thinking.

 

[Nordin]

Captndrydock source for parts for your rebuilt is Franz Marine service.
He might not have the Wiseco pistons if you have to change pistons.
Franz was a dealer back in the days and now he is 80++ and want to sell out all and retire.
He has or can give you advise where to find parts for your rebuild and he is really service minded.
Bill Kelly at Mastertech Marine is another one that is good to talk with.
He has got a bunch of experience in OBs and Mastertech Marine will have parts too for your rebuild.

 

[ct1762@gmail.com]

Thanks for the detailed response MC! Yeah, that's exactly what I was thinking too. That ring landing had wallered out. Okay, I'm convinced and will adjust my thinking.

the ring side-clearance tolerance in the piston is a whopping .004''. can you measure this with a feeler and get back to us? personally im not puttng a motor toghether with even .003'' but thats just me. the side effects include fun things like the motor feeling like its tied to a stump out of the hole, harder starts when warm, and general clatter at idle, and reduced service life. not exactly ideal.

 

[ct1762@gmail.com]

Dunno about engine machining costs over there but I got a rude shock when I wanted my ( 2 cylinder )18hp tohatsu bored.......180 bucks per pot ......I bought a brand new block for $305.
Last time I resleeved a block it was a 70hp johnson and it needed honed and decked .

sounds like you found a shop with a big fancy CNC machine thats set up for boring auto engine blocks. the absurd price is because it will take the guy a while to re-calibrate and set up the machine for your little tohatsu. flagship marine in punta gorda, FL is $35/hole finished.

 

[cyclops222]

No cheap AI in CNC machine land.

 

[Mc Tool]

sounds like you found a shop with a big fancy CNC machine thats set up for boring auto engine blocks. the absurd price is because it will take the guy a while to re-calibrate and set up the machine for your little tohatsu. flagship marine in punta gorda, FL is $35/hole finished.

Nah , They do all the local small engines and are well set up for small bores , just like everything else in New Zealand ....." you want what ? bend over and drop your pants "

 

[Captndrydock]

the ring side-clearance tolerance in the piston is a whopping .004''. can you measure this with a feeler and get back to us? personally im not puttng a motor toghether with even .003'' but thats just me. the side effects include fun things like the motor feeling like its tied to a stump out of the hole, harder starts when warm, and general clatter at idle, and reduced service life. not exactly ideal.

Sure, I'll check that out and compare the others.

 

[ct1762@gmail.com]

Nah , They do all the local small engines and are well set up for small bores , just like everything else in New Zealand ....." you want what ? bend over and drop your pants "

" you want what ? bend over and drop your pants "... ah the ole' "flipped over , unzipped, and done bone dry" scenario

 

[tg3690]

" you want what ? bend over and drop your pants "... ah the ole' "flipped over , unzipped, and done bone dry" scenario

And not have the common decency to provide a "reach around".......