Spun Prop???

MaddyDean

MaddyDean

New Member
Nov 25, 2009
545
Great South Bay, Long Island N.Y.
Boat Info
280 Sundancer, 1991
Engines
Twin 5.7 Mercruisers w/alpha drives
Hi All

I will try to be brief and to the point: The Issue
  • Went out on Saturday and in the middle of the bay we stopped to watch the sailboat race--While idling, I heard a very faint clunk, clunk clunk coming from the port side out-drive.
    • I shifted the throttle back and forth--seemed to be having a hard time finding neutral--and clunking went away.
  • We than proceeded and powered up both engines--Heard the noise louder this time and the boat was just about on plain when I backed off.
  • I then powered up the starboard side and did not hear the noise
  • I then powered up the port side and heard the noise and immediately backed off.
  • I did notice a noticeable difference in the prop wash--starboard side looked normal, but the port side seemed aerated and had no thrust.
  • I came back to home on one engine
  • At home-port I raised the out-drives (Trailer switch) and looked for barnacle, there were one or two small growths on each prop and nothing on the drives themselves.
  • I put the Port side in gear (counter rotation) and could not turn it by hand forward but could go backward
  • I did the same with the starboard side and had the same experience.
  • I did not try to forcefully turn the drives.
I am thinking perhaps hoping for a simple spun prop however, if it wasn't for bad luck I would have no luck so I wanted to reach out to you all to see other things I could check.

Before you do, full disclosure, at the beginning of the season before splash-down, I had DE-winterized with the rabbit ears and at that time I noticed that even though I was able to start the port engine, the prop was spinning very slowly. After moving the throttle back and fourth it stopped. I had called my marina mechanic to check and make adjustments--they did and all seemed fine until this weekend.

They never made any adjustments in the water, only on dry. I am being told by others that the only real way to adjust is in the water.

Could this be a, fingers crossed, simple adjustment?

Many thanks for any insight.

http://clubsearay.com/showthread.php/44405-drive-slips-out-of-gear-at-high-RPM?highlight=spun+prop
 
From what you wrote, it does not sound like a spun prop. It is easy to check. Just pull of the prop and check the hub assembly. If it is spun, the corner of the plastic hub will be rounded off. It sounds like a gear problem to me. How the drive oil? Is is low, or discolored?
 
Alpha 1 Gen-2's, the only way to check the drive oil is to haul the boat drain and replace.

The drives were both serviced at the end of last season by the marina. I would have to assume, for the time being, that they did the service and that the oil was replaced.

That written, i am making an appointment for a mechanic to look at it--while I am waiting, I wanted to see what I could check. Checking the gear oil would have to wait until they get to the boat unless I find the cause before then.

Thanks,
 
That doesn't sound like a spun hub to me either. When I spun a hub I never heard any clunking. I just lost thrust above 1200 rpm's and then the rpm's would shoot up. If I idled it would operate normally and I usually limped back to port like that.
 
"When I spun a hub I never heard any clunking. I just lost thrust above 1200 rpm's and then the rpm's would shoot up. If I idled it would operate normally and I usually limped back to port like that. "

Ditto......exactly just like that for me too last month. But mine first let go at 4000 RPM and scared hell out of me.
 
Sounds like a shift adjustment problem... the clutch dog bouncing off the gear due to partial enagement.
 
Just came back from the boat-- lifted up the hatch and Started her up and clearly heard the noise without putting her in gear.

I thought it was the engine, took her on one engine just around the bend to my mechanic. As soon as he had me turn her on he seemed to know what was wrong.

He said the engine sounds fine and that the noise was from the out-drive--probably the lower unit but won't know for sure till he hauls her tomorrow. He mentioned the Dog prior to me starting her up but after starting her, said it wasn't.

regardless, he said it should be ready by Thursday--no estimates on cost but he has been good to me the last 5 years on this on my first boat. Lent me tools and demonstrated things in the past to let me do things myself so I am comfortable with him.
 
If you have a boat, you have problems to solve... Having a mechanic you can trust is priceless... I hope you are back in business by this weekend...
 
rcknecht said:
If you have a boat, you have problems to solve... Having a mechanic you can trust is priceless... I hope you are back in business by this weekend...
Click to expand...

Thanks, I appreciate the well wishes. I happened to catch him at a lull. He has one boat he is splashing today and will be on my boat by noon--quote by 1:00.

He said he can squeeze me in if it is what he thinks it is but i had to promise that if he fixes it, I have to have it out of his basin this Thursday because he has other boats coming in.

I told him no problem as you could imagine.:grin:
 
:smt021:smt021:smt101

Just heard from my Mechanic--good news/bad news.

Good news is, the problem is in fact the lower unit on the port side. The bad news--it is a counter rotation drive and there are none around.

He located one direct from Merc but, you guessed it, it is very expensive and has a long lead time for delivery--would not be completed till next weekend--not the worst thing but still...

he proposed another solution, change the lower unit out with a standard rotation, new prop and switch the linkage and the forward controller lever.

I asked if I would notice the ride was different and he replied, "Yes" he said mainly when docking and in no wake I may be correcting more then I am now.

Question to you all, any experience with two standard rotation drives?
 
had counter twin outboards on my old LoneStar
had to change one out and from that point on had to run at idle with one tab down to hold a straight line.
and had extreme torque steer on heavy acceleration.
experience given for what it is worth.
 
I would look around and find one from a suppler online... There is got to be one out there in stock. I would want the counter rotating prop, and would not want to do a workaround...
 
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