blown piston

[jhpate]

Hi guys!

Got a 92 merc 150 that has bad cylinder with no compression. Can you look at this photo and tell how much will need to be done to this cylinder? Would like to get back to workink as inexspensive as possible . Boat is a 92 procraft and not really worth putting a lot of money into it. This is the top right cylinder. The top left cylinder was down to 80 on cold compression. All of the rest 105-110. Can this cylinder just be honed out or will I need to bore for oversize piston? Bad carb cause this damage?

thanks

[150aintenuff]

never know for sure unless seen in person... but that looks lie it needs bored .015.... and a new pistin.... not to bad really but it may need to go as far as .030 over sized... atleast there was SOME compression.... seen alot better show less compression....

bad carb runing llean can cause that without any problem.. as would lack of oil..

[mercpunk]

well one thing for sure ... you can join the club :D

[jhpate]

zero compression on the cylinder shown.:(

[mercpunk]

I would hone it and throw in another piston that is standard ... how far are you twistin in the rpm's ???? it does look lke lean or lack of oil :confused:

I mean you did say as cheap as possible ... but you never know a little J&B never hurt :)

[jhpate]

Wouldn't be turning over 6000. Fishing boat. Just like to get it cranking again. Thanks again for the help.

[150aintenuff]

try hone first just to see how deep the scores are i have seen some clean up.... then if its still rough bore it to .015...

[jhpate]

I'll do. Thanks for the advice. I'll have to order a hone.

[jhpate]

What is the best place to order ball hone from? What size and grit?
thanks

[TD]

You need to do something about the cyl thats down to 80 also. Pull the head and see what you find. Wouldn't want you to get it done and then have the other one melt. Something is wrong and you may catch it before it goes poof.

[j_martin]

I don't know all that much about these engines, but I don't think you want to ball hone a ported cylinder, except maybe a real light kiss at the end. I think you'd wind up screwing up all the ports.

In fact, if it were mine, I'd go find someone that knows what they're doing to hone it and maybe give me some helpful advice on assembly.

hope it helps
John

[jhpate]

Hey thanks for the responses. Doesn't the top cylinder on each side feed off the same top carb? I was planning on rebuilding carbs (with some helpful advice I hope and a manual). I was also planning on doing away with the oil injection system. I have been reading posts on that today as well. There have been a bunch. That would make a really great sticky for the uniformed (like me) to read, especially if it had pictures and detailed instructions. I was planning on pulling the other head and re-ringing the other top cylinder if no damage. I was also planning on a new water pump kit and redoing the fuel pump. That should take care of possible causes of a lean cylinder I would think. I would like to do this without removing the powerhead if possible.

[jhpate]

I did talk to a local shop about rebuilding the motor. $3500. Just too much money at the moment.

[tlwjkw]

A ball hone won't cut it just for starters. Ya ain't gonna fix it without tearing it completly down. Tha main problem with doin' it on tha stump is gettin' tha cracked rod caps on right and gettin' all tha trash cleaned out. Doin' that through tha front is hard enough for tha VERY experienced guy much less a nube. Ya might "PATCH" it, run it a hour or less and tear it down again cause of tha same thing or a lot worse than what ya got now. At least its fixable "THIS" time. Buy a good (MERC) manual n jump in here with tha rest of us that don't and/or can't pay Marina prices. Just a suggestion on my part................T

[Euroski]

Would you fellow expert say the cause was cooling issues since it's scored 360* of the bore? Just trying to learn something...

[jhpate]

:D Anyone within driving distance of texarkana, tx willing to show me how to do it right the first time?

[ChrisXS2003]

Would you fellow expert say the cause was cooling issues since it's scored 360* of the bore? Just trying to learn something...

Not an expert but top (2) cylinders hot....I'd look at the water pump/pressure pretty close