THUMP THUMP... Spun Coupler? Sterndrive Shot?

[myoldboat2]

1974 Mercruiser 140 I/O
GM Engine 140 HP 4-cyl 181 cu.in.

not sure if this is related to the problem i had with the starter
not disengaging... thread here.

Got the starter disengaged, backed out gently, then into forward and
a little throttle... thump thump... very little forward power, no reverse gear,
then no forward gear, then temp gauge goes up. I think the engine was
spinning on the coupler. Not sure if the prop hit something (it's bent at the
ends but not torn apart) or if the sterndrive gears locked up or both.
I'd like to fix this in the next 3 weeks or so... this vacation is shot but we
have more boating plans for the kids.

QUESTION 1:
Is there any way this could be related to the starter not disengaging?
I was thinking maybe an engine bearing was going or something, causing the
flywheel to rotate off center and mess up the starter, but none of it makes any
sense to me. When I got the starter disengaged, the engine sounded
absolutely normal. Is this just really bad luck?

QUESTION 2:
Once I get it home, how do I check the sterndrive? I guess I can try rotating
the prop if I can get the drive in gear, but I assume I'll probably have to pull the
sterndrive to check it?

thanks in advance.

 

[woosterken]

Re: THUMP THUMP... Spun Coupler? Sterndrive Shot?

could be a bad u joint,or maybe the center of the prop,put a line on thr prop shaft and the prop and start it on muffs,check to see if the line is still lined up if not the center rubber in the prop is bad.for the heating problem,if you hit mud or sand with the chewed up prop it could have put some in the impellor.

woosterken

 

[xltier]

Re: THUMP THUMP... Spun Coupler? Sterndrive Shot?

1974 Mercruiser 140 I/O
GM Engine 140 HP 4-cyl 181 cu.in.

not sure if this is related to the problem i had with the starter
not disengaging... thread here.

Got the starter disengaged, backed out gently, then into forward and
a little throttle... thump thump... very little forward power, no reverse gear,
then no forward gear, then temp gauge goes up. I think the engine was
spinning on the coupler. Not sure if the prop hit something (it's bent at the
ends but not torn apart) or if the sterndrive gears locked up or both.
I'd like to fix this in the next 3 weeks or so... this vacation is shot but we
have more boating plans for the kids.

QUESTION 1:
Is there any way this could be related to the starter not disengaging?
I was thinking maybe an engine bearing was going or something, causing the
flywheel to rotate off center and mess up the starter, but none of it makes any
sense to me. When I got the starter disengaged, the engine sounded
absolutely normal. Is this just really bad luck?

QUESTION 2:
Once I get it home, how do I check the sterndrive? I guess I can try rotating
the prop if I can get the drive in gear, but I assume I'll probably have to pull the
sterndrive to check it?

thanks in advance.

put the drive in gear and step on the prop blade ccw.thats forward.and check for spinning in the coupler.that would cause your overheating also cause the raw water pump isnt working.

 

[Wakesilver]

Re: THUMP THUMP... Spun Coupler? Sterndrive Shot?

When my coupler went, there was smoking rubber, bits in the bilge, and the motor rev'd without making the boat go at all. Mine did not overheat since I idled it home so the impeller kept sending water to the motor.

 

[myoldboat2]

Re: THUMP THUMP... Spun Coupler? Sterndrive Shot?

thanks, those are good replies. going to do the 4.5 hour drive home today. need to develop a plan of action to see what's wrong. at home, the boat will out of the water, and can be run on muffs. i've read this and other threads i could find on the subject. i guess this is what i'm thinking so far;

1. not running, try to put it in gear and rotate prop as xltier said.

2. check the sterndrive gear lube for metal.

3. paint the prop line per woosterken, try running on muffs to see if the problem is still there and if the prop stays lined up. look for coupler pieces per wakesilver. question: if the u joint went, do they usually separate, or does the coupler go with them? i can try to get some good light in there to see if the drive shaft behind the coupler is being turned.

4. i assume the next step would involve pulling the sterndrive or the lower unit. which would be next? pull the whole drive to check the u joint, or pull the lower unit and see if it turns correctly?

5. with the sterndrive off, i should be able to run the engine briefly to see if it is running correctly. i could run hose water into the cooling input if necessary, but i think the engine is ok, so a brief run without water should be ok?

i wanted to add that when the engine was running and the drive wouldn't shift, there was a scraping noise coming from the rear of the engine compartment. not sure if it was the coupler turning about the sterndrive driveshaft, or the u joint, or what.

any comments on what i should do in what order would be great. thanks.

 

[myoldboat2]

Re: THUMP THUMP... Spun Coupler? Sterndrive Shot?

got through #1 and the coupler has failed. i'll pull the sterndrive to confirm, then pull the engine.

damn.