1971 or 72 grew omc (gm) 120hp no forward-reverse!!

[Joeshow]

hi,
my first boat, got it running real nice for about ten minutes, maxed out at 3800rpm. she was alittle warm, 3/4 on the temp gauge when she stalled out. tried to re start it, nothing, engine wouldnt even crank. waited for about ten minutes and she fired right up with alittle knock so i let it cool down some more. half hour later, fired right up but no forward or reverse!!!

i believe she over heated and the gauge is inaccurate. i had the most water coming out of the water output then ever prior to driving it, it spits some air i noticed too? i have checked the engines water pump and thermostat, pump seems fine, left the thermostat out. i have a good stream at the intermediate housing out of both water ports on the top.

now forward and reverse, with both, the engine will rev up some, then if i give it more gas, she dies.

do i need the forward and reverse clutch pack kinda things? can you guys tell me what i need to buy, by what i have explained?

i have a manual coming in the mail but have no idea when it'll get here. i'm quite able to disasemble an engine and such. i'm just new to boating and the parts that come with it lol

thank you for your time!!!

 

[SeanMcl]

Re: 1971 or 72 grew omc (gm) 120hp no forward-reverse!!

now forward and reverse, with both, the engine will rev up some, then if i give it more gas, she dies.

Do you get a "clunk" when forward or reverse engage, and then the motor dies?
I am trying to come up with a way that an overheat could cause issues with the electric shift, but all I can think of is that the shift wire was close to the exhaust risers and melted causing a short.

Or does the shift engage, start turning the prop a bit and then the motor dies? If so, then you are just looking at the usual overheat suspects: burnt valves, broken ring, stuck valves, warped head, etc. Have you changed the oil and run a magnet around in it to see if you come up with any small chunks of anything? Pulled the plugs to make sure they are still good?

 

[Joeshow]

Re: 1971 or 72 grew omc (gm) 120hp no forward-reverse!!

thank you,

no there is not a clunk when i put it in forward or reverse, prop does not spin... dont really hear anything from the out drive :/
i haven't drained the oil, just checked the dip stick, didn't see any metal flakes or anything. this was minutes after the over heat. oil still looks clean.
i'm kinda thinkin it seems like the outdrive is seized?
i'll try turning the prop by hand once i get the boat home, in and out of gear.

thanks again for your time!!

 

[Joeshow]

Re: 1971 or 72 grew omc (gm) 120hp no forward-reverse!!

well the prop spins freely out of gear.... in forward, the prop only turns in the direction of forward, doesnt turn in the direction of reverse. in reverse, the prop only turns in the direction of reverse, doesnt turn in the direction of forward.
i tried to turn the ball joint thing, where the out drive meets the transom, i could only turn it a tinny bit back and fourth.
started the engine and tried forward and reverse, still getting the same responces. no clunks or nothing...

Please help!! i am stumped!!

 

[Joeshow]

Re: 1971 or 72 grew omc (gm) 120hp no forward-reverse!!

Well, it turns out that it was the upper vertical drive shaft seized, no oil in the upper :/.... never believe when you buy, and the guy says its been changed! Lol