Video of 1957 35 hp please help

[vintin]

Sure sounds like pre ignition from overheating even early in the video.

Gets louder until sneeze and seize.

[outbdnut2]

Just a thought – Has the shift rod detent mechanism been checked to be sure something isn’t broken or missing, allowing it to shift into neutral? And – when it goes to neutral, does the shift handle move to neutral? Even if something is wrong in this area, I think there is something else going on as well.

Also – I watched the video again on a 39 inch computer screen and it’s hard to tell, but watching the throttle position indicator knob, it looks like the throttle has been backed off immediately after the problem reared it’s head, so maybe it’s not slowing down and quitting due to overheating?? Please confirm if you backed down the throttle.
Dave

[fisherman6]

I agree that the throttle was backed off at the end of the video when the engine stopped. It looked like it was run at full throttle for a short time, then backed off to maybe 3/4. Right after it was backed down a bit is when it bucked hard The first time. The engine slowed down and got progressively noisier as the boat came off plane. The engine continued to slow and sound more labored until the throttle was backed off further and it screeched to a halt as it was being reduced to idle.

I had my 54 Super Fastwin overheat due to a blockage in the cooling system and though the engine is half the displacement of this one, it was a very similar event with less knocking noise. My engine had a blockage of dirt, grease, and dead bug carcasses behind the bypass plate on the lower unit. At idle it was pumping lots of water. Once I was moving at any speed the water that is supposed to enter through the screen behind the prop could not reach the pump. It was only getting a very small amount of water that was passing through the holes in the bypass plate at speed. That was just enough to save the impeller, but the engine overheated.

It started slowing down and I started smelling something hot. I backed the throttle off and by the time I got the tiller grip to half throttle the engine came to an abrupt halt. I was lucky enough to not cause any permanent damage to the powerhead but the gaskets all leaked afterward. I went through the powerhead with all new gaskets after finding the blockage and the motor is fine and a great runner still. I’m sure it wouldn’t take too many more cycles like that to ruin it though. Your motor looks to be in great condition, but if there is some blockage in the water pickup from behind the prop; even paint on the screen from any repaint that may have been done in the lower unit(s), leaky water tube grommets, blockage in the water tube, or whatever else; this can lead to overheating. Maybe I’m totally on the wrong track, but if my experience can help someone else I feel like it is worth sharing.
-Ben

OldJohnnyRude on YouTube

[frankr]

That brings up another thought—rare, but not unheard of. At speed, water is force-fed by the prop to the water intake screen, just aft of it.
Anything wrong with that screen or the plug that holds it in will cause overheating at speed but not at slow speed. This is often seen in other motors than this one.

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