you don’t see this everyday

[johnyrude200]

Super-imposed text should indicate enough. NOTE top end died off after 5 seconds of WOT (still pushed my 14′ 1968 starcraft about 26MPH then would go into an instant overheat within 2-3 seconds after that top speed even with this 1 melted piston…).

This was my 2nd motor owned 5 years ago (when I didn’t know my head from my other end) and the reason why I’m a full time mechanic now. Thought I sent this to the scrap yard back in 2013, but recently have been re-organizing my inventory and stumbled upon this buried 4 layers down, so couldn’t resist hearing folk’s opinion.

[frankr]

Pre-ignition/detonation.

[billw]

25s had a lot of trouble with head gaskets, especially in the salt. As long as they didn’t sit idle, though, they would just go and go and go, running like crap. Shell fisherman were famous for this. I am not disagreeing with Frank. It’s just that the picture looks all to familiar.

Long live American manufacturing!

[fleetwin]

Well
I won’t pass judgement on Owen’s Marine, without seeing the workorders.
In any event, doesn’t look like the aluminum has separated from the sleeves(s), which was not uncommon for these engines in the salt water. This piston was in the midst of melting down due to preignition. To be honest, something as simple as a loose spark plug can cause preignition. How badly is the piston melted? Are the rings stuck, cylinders scored? If not, this old dog might run again with the usual clean up and servicing. I know, what am I thinking, but it is possible if the piston dome isn’t too badly melted/rings/cylinders not too messed up. Pull the intake cover off and have a look, I’m guessing the exhaust cover screws are good and stuck, so don’t mess with them.

[frankr]

Wonder if the guy milled the head or something? Those motors were already souped up, so increasing the compression ratio could cause the pre-ignition.

[johnyrude200]

I do recall this motor having the top plug hole with a helicoil installed to clean up the threads. Believe it or not, this was a fresh water motor, and even with the melted piston still showed fairly high compression.

The cylinders are still in good shape, and I may just swap out the piston this winter yet for sentimental reasons. Im still surprised I still have this powerhead!

As for owens, their 5,000sf location with its contents, along with 6 acres, were auctioned off last week for $365,000 and back taxes, utilities, and one heck of a EPA rapsheet.

They folded, partially, because they lost all their dealership licenses by pulling manuevers on people like getting paid for warrantee work by the manufacturers, then still charging the customer to double dip, then getting caught by the manifacturer. Well, that and going through 3 bankrupcies.

[fleetwin]

A poorly installed helicoil can cause preignition. Looks pretty ratty for a fresh water motor, probably due to all the overheats. Milling the head surely could be the culprit as well. These engines were pretty high compression/high output back in the day, so they are certainly running on the edge today, like Bill said.

[johnyrude200]

yeah, some explanation behind the appearance is it sat outside with the head off, under cover, two winters ago before I got ‘organized.’

Fortunately I did spray oil into the cylinders so no rust in there, but the rest of the motor accumulated the usual weathering.

The helicoil installed wasn’t the sleeve type, it was the screw in wire type. So that was wrong. I suspect that a portion of that may have broken off into the cylinder and stuck to the piston, lit up like a christmas tree, and melted the piston down. Who knows. The cylinder head had melted aluminum all over by the plug orifice on cylinder #1.

[rmhxruss]

Hard to believe that five seconds would do that much damage.

[johnyrude200]

Well, the overheat happened at WOT after about 30 seconds (it was pumping tons of water, and the T-stat had been removed too). The 5 seconds was meant to indicate the motor would get up to WOT/high RPMs, then as it was overheating (quickly), the power would die off. I’m just impressed it even got up to high RPM and still had power despite a melted piston.

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