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Omc 1978, 120 hp.

U

Unlucky omc 1978

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Hi.
I'm desperate for advice. I recently bought an old daycruizer with an omc 120 hp engine (1978). I'm guessing that means I have a sterndrive 400? It looks like it from pictures I've seen online at least.
When I bought the boat, and drove it home, everything worked great. The next day, everything worked just fine as well. The third day, I desided to bring the wife and kids along for a day on the fjord. We put out from our dock and brought the boat nice and easy up to a good speed. And then the engine suddenly revved up, and had no power forward. I immediately killed the engine, raised the drive out of the water to check if the propellar had fallen off or something. But that was still there. I then lowered the drive again and attempted to start the engine and put it in gear. Both forward and reverse was tried, but no go. We luckily got towed back to our dock. But now I'm at a loss, since I have NO knowledge about engines and drives.
What can this be? I've tried putting it in gear with the engine off, to feel for resistance when turning the prop manually. There is some resistance both forward and reverse.
When this happened there was no foul noise or anything to indicate anything was wrong. It just lost power.
I'm Norwegian, so I appologize for any misspellings that may have occured in the making of this desperate post on your forum. I hope someone has experience with similar cases and can guide me along.
Thank you.
 
does your drive have exhaust through the center of the propeller? (just to verify it's a 1978 and not a 1977 as the method of shifting is completely different between the two)

any grinding or other noises when attempting to shift?
any propulsion at all? Was the propeller even trying to turn?
did the engine start overheating after propulsion was lost?
 
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This is a 4 cyl right ? There is a longer hose going to the t stat take it off with drive in water and start engine if little or no water come out of that hose it will likey be shaft the runs water pump then goes down to prop. You can get the parts here. change the water pump at the same time. Thats what I did. and it works great
 
Thanks for now guys. It will have to wait till I Get back onshore from my two week hitch on the oilrig. There may be more questions if this is not the reason.

btw. Is the changing of parts difficult for a handy diy guy with NO engine or mechanical skills?
 
Here's the test.

Put the ignition key in your pocket.

Put the drive in forward, turn the prop,if the prop turns, the ball gears move it's the coupler.

If the ball gears do not move and the prop turns it's the shafts.
 
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