'92 Merc ELPTO 50hp 3 cyl rebuild

[smudge]

My Merc overheated a while back, I have been using it and it was down on power. The inevitable happened and it went knock knock knock..... I have it in a zillion pieces now and the top piston ring has broken, snagged on the transfer port scoring the bore & dinging the combustion chamber. The other pistons have seize marks although it never locked up and there are scuff marks on the bores but nothing bad. Is it repairable? I think a hone would keep cyl 1 & 2 happy but #3 definately needs boring. Would it be worth repairing? Thanks.

 

[achris]

Re: '92 Merc ELPTO 50hp 3 cyl rebuild

in my opinion, yes....

Cost up a new piston, new rings for the other 2 pistons, a gasket set and the machining.... Can you buy a replacement engine, in as good condition, for that? If so, go buy it. If not, fix your engine....

Chris.........

 

[smudge]

Re: '92 Merc ELPTO 50hp 3 cyl rebuild

Thanks for the reply. One more thing, the broken ring has dinged up the combustion chamber & although I dont think it matters too much I thought I had better ask in here.

 

[achris]

Re: '92 Merc ELPTO 50hp 3 cyl rebuild

As long as there are no sharp edges that could get hot and be a source of pre-ignition, then you should be ok...

Chris.......

 

[saumon]

Re: '92 Merc ELPTO 50hp 3 cyl rebuild

The other pistons have seize marks although it never locked up and there are scuff marks on the bores but nothing bad. Is it repairable? I think a hone would keep cyl 1 & 2 happy but #3 definately needs boring. Would it be worth repairing? Thanks.

I tend to diagree with Chris, altought he know this stuff a lot more than i do.

If, like you said, the pistons of the others two holes expand enough to leave scuffing marks on the cylinder bore, i highly doubt that a honing will do the job.

A simple test consist of running your fingernail across the marks. If you can feel them, you need to rebore and put oversized pistons. If you can't, you're good with a honing and new rings.

 

[achris]

Re: '92 Merc ELPTO 50hp 3 cyl rebuild

I tend to diagree with Chris, altought he know this stuff a lot more than i do.

If, like you said, the pistons of the others two holes expand enough to leave scuffing marks on the cylinder bore, i highly doubt that a honing will do the job.

A simple test consist of running your fingernail across the marks. If you can feel them, you need to rebore and put oversized pistons. If you can't, you're good with a honing and new rings.

I agree with you.... However, often what is felt is piston metal on the bores, and that can clean up with a hone, and just a little scuff from the piston can be ok.. I was taught by a very experienced Merc state service manager that you can sometimes get away with cleaning up the piston with some emery. But then every case is different and without seeing the piston it's difficult to assess.

If the bores are grooved, than that's a completely different kettle of fish, and it will need to be bored and new, oversize, pistons fitted.

Chris.........

Chris.........

 

[saumon]

Re: '92 Merc ELPTO 50hp 3 cyl rebuild

While you were here, you should also check the piston side of your connecting rods, particulary the one connecting to the piston that seized. I once rebuild a 1993 60hp 3 cyl (same engine as yours) that overheated and, to my surprise, i could easily fit 30 or even 31 needles bearings instead of the standard 29 around the piston pin. For some reason, the end of the rod had ?elongated? and the diameter was something like 0.020 inch greater than the others (i don't remember exactly), maybe due the the heat and the shock when it seized.

BTW, here's the link for the OEM service manual of your engine:
http://rapidshare.com/files/213240341/45jet-50-55-60.rar
password is ?ribforum?

(sorry for my english, as i'm french speaking!)

 

[smudge]

Re: '92 Merc ELPTO 50hp 3 cyl rebuild

Ok thanks.I would give the two lower cylinders a hone first then make a call on boring them. The piston skirts are scuffed on an area but it doesn't extend to the rings or the bottom of the skirt and would clean up ok. The dings will get smoothed out to remove sharp edges that may cause pre ignition, not sure if they would affect the structural strength of the head. To be honest I haven't had a good look to see if there is a water jacket in the area and that is my concern. It appears not, is it just the cylinders that are cooled? Thanks again.