115 Tower 4 th piston burnt

popknot · Jun 26, 2012

This is an update to my previous post "I think I mighta blown it". I took my 1986 115 into the mechanic he checked the compression for me and the 4th cylinder is out. 20# all the rest checked out ok roughly around 140#. I looked down inside the cylinder as best I could and it looks like the piston is almost melted on top. Like it got real hot. I really like this old engine and really don't want to give up on it. Any advice on what route I should take at this point. Thanks for any and all help.

John

tysdad2010 · Jun 26, 2012

Re: 115 Tower 4 th piston burnt

popknot said:
This is an update to my previous post "I think I mighta blown it". I took my 1986 115 into the mechanic he checked the compression for me and the 4th cylinder is out. 20# all the rest checked out ok roughly around 140#. I looked down inside the cylinder as best I could and it looks like the piston is almost melted on top. Like it got real hot. I really like this old engine and really don't want to give up on it. Any advice on what route I should take at this point. Thanks for any and all help.

John

what I plan on doing is...If it is only one cyclinder messed up... take the powerhead to machine shop have them cut the cyclinder the same size as the rest of them then sleeve it...and rebuild the cyclinder...I beleive that is what my guy said he is planning on doing ...thats the cheap way out ...he doesnt like to do it like that he rather through a new powerhead on it and be done but if that is what the customer wants that is what he will do...it will cost about $1200-$1500 to rebuild the 1 cyclinder that is with him doing the Labor at basically NOTHING at all...because he is my best friend

but if you have the money the BEST route is to through a new powerhead on and be good to go...BUT MAKE SURE TO BREAK THE NEW POWERHEAD IN TO SPEC dont just go out there and give it hell or you will be right back at square one!

popknot · Jun 26, 2012

Re: 115 Tower 4 th piston burnt

Thats kinda what I was thinking too. I've done it with car engines before and then ran them for a long time just hone and re-ring the cylinders that are still ok, then rebuild the one bad one. The mechanic I went to said somebody might do that for me but he didn't want to do it and didn't recommend it. He said the same thing about 1000.00 to 1500.00 to have that done. He said shop where I would have to send it charges about $200.00 per cylinder to bore it over and sleeve it. His recomendation was try to find a late 90's to early 00's motor to put on it and forget about this one. Said todays fuels are real hard on these older 2 strokes. But I don't know I like this old Tower of Power and really would like to fix it. I kinda feel like Id be throwing my 1968 camaro in the trash. Like I said its not an investment I'll never recoup my cost back out of it. Its a toy and big boy toys cost lots of money.

bunker108 · Jun 26, 2012

Re: 115 Tower 4 th piston burnt

I think that rebuilding number four is a good idea too. Get a set of rings and a gasket kit and do what you can while you are in there. Pulling the power head is easy, it took me a couple hours last Saturday to get mine off and into the garage, and I have never done it before.

I was looking for a repower too but it is discouraging after looking at junk and old engines that people wanted too much money for. If all else is good with your engine, go for the rebuild, and fix what needs attention while it is out.

Good luck!

jimmbo · Jun 27, 2012

Re: 115 Tower 4 th piston burnt

Is the cylinder so badly scored it needs resleeving? There are 3 sizes of oversize pistons avialable.

popknot · Jun 27, 2012

Re: 115 Tower 4 th piston burnt

jimmbo said:
Is the cylinder so badly scored it needs resleeving? There are 3 sizes of oversize pistons avialable.

Thats what I'll have to determine. So I guess disassembly is the next step, then I should be able to see just how bad the damage is. If that cylinder wasn't getting proper lubrication, what about the others? I should be able to disassemble the powerhead myself. Now the re-assembly, thats gonna be more tricky. Not sure if I can handle that or not. The mechanic that checked it out for me told me you can either do each cylinder individually, in which case you have to replace all the crank bearings. Or you can lift the crank, pistons and all out of the block, but I would think that would be quite tricky to get it all back together properly. Does anyone know where I can get a GOOD shop manual? What about a re-manufactured powerhead anybody know where to get one of those at the best price? Thanks again. Please keep all the helpful info coming its much appreciated.
John

canoemang · Jun 27, 2012

Re: 115 Tower 4 th piston burnt

I am rebuilding a 1986 merc 115. So far it hasnt been as hard as i expected. i'll be dropping in one cylinder at a time.

My 3rd,4th and 5th piston lost some rings due to.. unsure..

Here is my thread..

http://forums.iboats.com/showthread.php?t=556659&highlight=hone+deglaze

I get my new parts today and i'll be honing (3"flex-ball hone)all 6 and 3 new pistons and new rings on all 6.

As long as it goes as expected i have a 84 that needs to be rebuilt, that is next on my agenda.

popknot · Jun 27, 2012

Re: 115 Tower 4 th piston burnt

I see there was some discussion in your thread about wheather you should bore or could get by with just honing. Did you use the muriatic acid to clean the cylinders as suggested. Measure all the bores? etc. Honestly after reading your post I'm thinking I might better have someone do it for me as I have none of those micrometers, hones etc would have to buy them all (and would probably never use them again)and then would probably have a less than desireable rebuild as I have never done this before and still not be that much money ahead after figuring cost of all tools etc. Plus its summer boating time right now, might just bite the bullet and try to find a re-man powerhead.

canoemang · Jun 27, 2012

Re: 115 Tower 4 th piston burnt

I'll be doing to wash yes, the micrometers and hone gauges aren't that bad, i think i got mine for $50.00 for both. and if you run as hard as i do, you might be in this situation again and appreciate having the tools and the knowledge.

I do know what you mean about summer boating, ive missed 2 weeks so far and it is killing me..lol

Good luck on whatever route you go.

popknot · Jun 27, 2012

Re: 115 Tower 4 th piston burnt

Yeah not sure what to do. Finding out from these posts theres alot I don't know about these engines. And as you said in your post everybodies got an opinion, often conflicting and hard to tell whos correct. The really scarey part is I might spend all this money and if I don't find what caused it to happen in the first place I'll just burn up another powerhead. Don't know which way to go.

canoemang · Jun 27, 2012

Re: 115 Tower 4 th piston burnt

Yea.. i try to take opinions from people who i have seen post on here a lot and have always seemingly had knowledge of these L6 mercs.

I am not ready to give up on my Merc 6 Cyl, i think they are great motors and with some learning and help i am further along than i expected.

What ever direction you go, good luck man.

redjmp · Jun 27, 2012

Re: 115 Tower 4 th piston burnt

OK I have an 86 115 that lost 10lbs in #4 due to a leaky inner water jacket gasket.
Probably whats wrong with yours too.
Did you find rust or bits of metal on your #4 spark plug?
It is highly unlikely that only #4 melted as 3 and 4 are both fed from the same carb so if one hole was running lean enough to do damage, the other hole should be just about the same.
Therefore I don't think you were running lean at all.
Just to be safe you should clean out that carb...
Whats with this resleeving nonsense?
That's only a last measure for an engine that has already been rebuilt and bored out the maximum....
All you probably need is new rings on #4 and maybe a light hone.
At the worst you might need to rebore that one hole for about $50 and replace the piston and rings with oversized ones. Less than $100 plus about $50 for a gasket set.
But down 20# isn't all that bad.
I would be tempted to just identify the cause and fix it and then leave the hole alone and see if you keep losing pressure or if it stays the same or even comes back.
You also just may have some carbon build up on the rings so try running some seafoam through first before doing anything and see if that fixes you.
Good luck!

popknot · Jun 27, 2012

Re: 115 Tower 4 th piston burnt

I'm sorry, not down 20# . 20# total compression in that cylinder sorry for confusion.

Faztbullet · Jun 27, 2012

Re: 115 Tower 4 th piston burnt

Get ready to put a set of packs on it......

popknot · Jun 28, 2012

Re: 115 Tower 4 th piston burnt

coil packs? How much is that?

popknot · Jun 30, 2012

Re: 115 Tower 4 th piston burnt

Found I guy on the internet who says he'll rebuild my powerhead for $1600.00. Just gotta remove the powerhead and ship it to him. Seems like a pretty reasonable price. Think I'm gonna go this route and have a local mechanic put it on and give it the once over before taking it back out.

jimmbo · Jun 30, 2012

Re: 115 Tower 4 th piston burnt

Why not have the local mechanic do the rebuild and install? That way is there are any problems, there can be no 'it's the other guys fault' blame game. It migth cost a bit more upfront, but it might save you a bundle of grief later as well as shipping charges

popknot · Jul 1, 2012

Re: 115 Tower 4 th piston burnt

jimmbo said:
Why not have the local mechanic do the rebuild and install? That way is there are any problems, there can be no 'it's the other guys fault' blame game. It migth cost a bit more upfront, but it might save you a bundle of grief later as well as shipping charges

I can't find a local guy to do it. Everybody keeps telling me its a dinosaur they don't want to mess with it, its not worth the money, you'll never get your money out of it etc etc. He did say he would take off the powerhead for me and put the rebuilt one on. But no one seems to want to do the rebuild for me.

canoemang · Jul 1, 2012

Re: 115 Tower 4 th piston burnt

Do it yourself and save a ton of money and a pita of shipping and dealing with an out of state mechanic..

I just starter tearing down my 84 115 merc tower and it really isnt as intimidating as you think. Get a good service manual, take pictures and keep track of parts etc..

My 86 rebuild was my first and was a bit intimidating... Running strong after 34 gallons of gas.. The feeling you get when you slap it back together and it fires up the first time is a great feeling of accomplishment!!

tysdad2010 · Jul 1, 2012

Re: 115 Tower 4 th piston burnt

I got quoted local...$2800 for someone to rebuild my whole powerhead,service lower unit and rebuild carbs...or buy a Brand new powerhead for $3800 that i can drop on and I get the lower unit serviced and rebuild carbs by my self or have my buddy do it

but if you are mechanicly inclinced do it your self like Canoemang said you will feel great knowing you did it your self and you will know for sure it was done right and the way you wanted it when it is all said and done...

115 Tower 4 th piston burnt

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