1978 115 siezed today

sony224422

Seaman
Joined
Jul 15, 2006
Messages
67
I was going WOT, after crusing at about 3.5 mph for 30 mins, and all of a sudden i lost power. It felt exactly like it did when my other 115 blew, 4 years earlier. So i slowed it down, hoping to limp back to the landing to pull it out of the water at least.

It siezed as soon as i cut back on the throtle. So after 2 hours of drifting, someone finally realized i wasn't waving and towed me back in. Upon reaching my house, i pulled both heads off. The starboard side was okay, which gave me some comfort because when i got the motor someone had stripped out a spark plug and i rethreaded it, worked fine. But thats also the side that blew on my old 115. So, i go to the port side, and pulled head. I can right away that the lower piston on the port side is done. There were tiny shavings in there, and the cylinder walls were completely dry and rusty, with some water in there. The cylinder wall doesn't appear to be scratched, but im sure it is. There was a little chunk off the piston that seemed to get smashed up in there. I think a connecting rod broke, because it seems to be a little twisted, and not in line with the one above it. Now, i had an extra set of pistons and a head for that side from my old motor, if the walls aren't scratched would it be worth trying to get it to run again? Also, what could have caused that? it doesn't seem like a ring issue like i had before, but that fuel wasn't getting to it or that water had gotten inside.

I was having problems a few days ago, and summed it up to be water in the gas, and after draining the tank and emptying the carbs i went back out and had no problems except for a little spot of hitting the bottom, and then it cut out for a stroke at WOT but resumed and was perfectly fine.

This motor was sitting for 4 years before i aquired it, so i really don't know if this was a problem before i got it, or if just happened.

I'll post up pics when i get a chance.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: 1978 115 siezed today

Well, you were correct about water, but it wasn't coming from the gas. More than likely a serious leak in the exhaust cover area, squirting water in through the exhaust ports. Unless you are able to make one motor out of two, it is ready for the bone pile. The crankshaft is probably shot along with the tossed rod.
 

sony224422

Seaman
Joined
Jul 15, 2006
Messages
67
Re: 1978 115 siezed today

i was also thinking that a reed valve got stuck closed and didn't allow fuel to enter that cylinder. Whats weird is there is actual rust on the walls, but it seemed to be running right before it seized.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: 1978 115 siezed today

The reed valve theory don't get it. You don't know how many motors I've seen where water intrusion came through the exhaust ports. Lots.
 

sony224422

Seaman
Joined
Jul 15, 2006
Messages
67
Re: 1978 115 siezed today

really, thats interesting. What exactly happens, cus it looks like water did get in there, and when i pulled the head water did come out from somewhere, im not sure if it was in the jacket or in the cylinder.

But the piston is really stuck, and i'll probably have to rebuild the powerhead. I just got this motor at the beginning of the season, after the boat had been sitting with the old blown motor on it for 4 years. I really hope i can get this thing back up and running, whether rebuilding the powerhead or getting a new motor.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: 1978 115 siezed today

The exhaust cover area (flat plate or bubble back) area between the V is the culprit. Can be a leaking gasket from prior overheating, or hole through the baffle plate, or hole corroded through the cylinder block. I've seen all scenarios.
 

mikesea

Lieutenant Commander
Joined
Oct 1, 2006
Messages
1,830
Re: 1978 115 siezed today

i have rebuilt many engines like yours,its true about exhust cover leaks,but we also found many times there are cracks that allow water to enter the exhust from the cooling passages,usually hard to see with the eye,but as the engine heats up these leaks get worse,inside the exhust cover on back of the engine,bottom of the block are two triangular shaped castings,the corners are what go,the tend to get alot of heat and warp causing cracks,not many people know about this,but after rebuilding an engine 3 times ,all new parts,same problem,3 of us cleaned the block ,we had an awesome welder that put a dye in different spots and after welding the cracks,trouble never returned,your engine is old lots of run time,be sure to check these areas before rebuilding if thats your intent
 
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