Johnson 60, blown powerhead

[Tagged]

I have a J60TLEDR, 1996 Johnson 60hp with a blown powerhead. The motor seized at 4000+ rpm. After cooling, the motor will turn about 300 degrees. It won't bring the top (#1?) cylinder to TDC.
Pulling the plugs, I find that the top plug appears to be coated with bits of melted aluminum. It looks like someone coated it with Christmas tree flocking. Enough to close the spark gap. The top of the piston looks like fresh hot-dip galvanize.

The bottom two pistons and plugs look normal.

2 questions: What likely caused that? and Is it likely still a candidate for a rebuild?

I would hate to send the thing in for a rebuild to find out that nothing can be done. If it isn't a candidate for a rebuild, what other options are there? Could I still just buy a powerhead and pay the core charge? I don't have the money for a new motor, so "boat anchor" can't be on the list of options, okay?

My timeline is to do the work this winter, and have the boat ready for spring break 2017.

Help?

 

[gm280]

Tagged, Sound like the top cylinder was running lean and got really hot. Hard to tell if it is rebuild-able without any pictures or measuring the bore. With the head off does the engine turn 360 degrees or not. If it still doesn't make a complete turn, then you have other damage yet to be discovered. If it does turn all the way, then you could be just in for one cylinder rebuilt. But that is an unknown without further investigation. JMHO

 

[emdsapmgr]

Heat was the problem on your engine. Either it overheated from lack of water flow through the powerhead, or the top cylinder ran dry (lean) and that was the cause of the overheat. Pull the top carb apart and see if you have any fuel flow blockages on any of the jets in the upper carb. Just because the piston went does not mean the top cyl is shot. You may be able to overbore it. (yes, you can overbore just once cyl in an overhaul.

 

[phillnjack2]

first of all, where is the tell tale on your block ? is it from the top of the block or is the tube connected to the side of the engine /
what is the part number on the side exhaust plate on your engine , it will be large enough to see very easy.
this engine could of slipped through without amendments done to it, tell tale should be on top of the block, updated exhaust cover, updated impeller, and drilled into water jacket inside the exhaust cover.
all these things are what causes the top to over heat and start melting stuff.
what I would do it put the top piston all the way down and look through the plug hole with a borescope (very cheap on ebay $20 buys a good one for android phone).
these are easy to use and will show you the cylinder wall. hopefully its not going to be scored to bad.
if it is then that cylinder will need either a hone or a rebore,if re-bore then do all 3 holes and then simply get a new piston / rebuild kit and proper omc
service manual.
DO NOT BUY any other service manuals apart from the omc for a omc engine, all the after market books are total waste of money and very wrong in many places.
but check out the exhaust plate number, and report back.

 

[Tagged]

Updating a very old thread, in case someone pulls this thread up in a search and wants to know the results. I never fixed the engine. I bought a shop manual and began a rebuild. But the motor was severely corroded from 20 years in salt water.

Six of the 14 head bolts broke off in the block, plus five more of the exhaust housing cover bolts, and two of the block-to-midsection bolts. I was unable to remove the bolts from the block, and a local machine shop refused to do the work, saying it was cost-prohibitive. I looked for several months for a replacement block, and never found one that I was happy with.

I eventually gave up on my rebuild effort and bought another old motor. I'm currently resurrecting an old freshwater Johnson 140, you can follow that thread here:

https://forums.iboats.com/forum/eng...ds/10527841-tagged’s-140-johnson-resurrection.