confusing problem from today...

[tmo]

here's my problem from today's run. I have a '06 merc 5.0 MPI and recently replaced my prop, put on a solas with supposedly the same pitch , adn specs as my orig merc prop. today I couldnt get the boat (Glastron GXL 205) to get any speed beyond about 5-10 mph. when I throttled down the engine would rev up but no torque from the props, it was as if they were not spinning? It would kind of buck but no sustained accelleration. Im a new boater and am at a bit of a loss. any suggestions?

 

[Phantom_II]

Re: confusing problem from today...

I suspect ya got the wrong hub for your drive and the propshaft is just spinning in the hub.

 

[tmo]

Re: confusing problem from today...

Thanks much.

is it possible that it would be fine at lower speeds event with the incorrect hub?

 

[bhammer]

Re: confusing problem from today...

Put a witness mark on the prop hub and line it up to a witness mark on the prop shaft. A chalk line will work fine. Put it into gear and see if you can rotate the prob by hand. This could be a spun hub or not the right one or an engine coupler or drive problem... If you can rotate the prop, and the witenss marks don't align, it will be the wrong hub.

What hub kit did you order with the prop?

 

[tmo]

Re: confusing problem from today...

I will try that, should there be any play at all in the prop, shaft?

I gave the prop shop the model number for the OEM prop that I had and they sent me a prop with the "proper" hub for my drive, I didnt know enough to specify a hub...

 

[tmo]

Re: confusing problem from today...

had a chance to look a little closer at my problem today and heres what \i have found.

with the boat in gear I could turn the prop by hand and there was a constant "slippage" every quarter turn or so. This was not in the hub though, but in the whole shaft? in reversre the same thing except the sound of the sippage was different, more like a clicking sound?

I havent really seen a spinning hub before so I wanted to try somehting else, I replace the prop with the old OEM one with its original hub and tried the same test. the results were exactly the same...

am I correct in assuming this is not a hub/prop problem? could someone explain better what a spun hub is for me? is the hub spinning free of the shaft or of the prop?


Im not sure who moved this thread to the prop section but if this is a drive problem I'd appreciate it if they move it to the proper forum...

Thanks

 

[Silvertip]

Re: confusing problem from today...

You didn't do the test that was suggested or you would know what the problem is. On a standard rubber hub prop, the propeller shaft has splines on it matches those in the hub of the prop. As the prop shaft turns, the hub turns, the rubber bushing between the hub and the blade are of the prop are bonded together so the rotary motion is transfered to the blades. If the bond in the rubber breaks, the hub can spin freely inside the blade are of the prop. In car terms, the wheel is spinning inside the tire so you go nowhere. If you bought a prop with an exchangeable hub system, you buy a separate hub that matches the splines on your engine. You can then use any prop that is designed for that hub system. So if you damage one of those props you simply replace the prop and keep the hub. The clicking you hear when turning the prop is the ratcheting of the clutch dogs. Perfectly normal. You should not be able to turn the prop by hand in the opposite direction. I suspect you are installing the props incorrectly or have the wrong props.

 

[bhammer]

Re: confusing problem from today...

tmo, Please perfrom the test as I laid out. Silvertip gave a great explination as to what sounds like is going on. If you feel it slip every 1/4 turn, you are probably feeling the hub slip as most I have seen are 4 sided.

Did you use the change hubs when you changed back to the other prop?

Make a mark on the prop shaft, the part that the bolt screws onto and a mark onto the prop. On most, you can make a mark across the hub and prop. You can use nail polish as well. Give it a try. If the lines don't line up, you have a hub problem. If the lines still line up, there are more problems but I don't think that is the issue.

I could be totally off base, but I want to fully eliminate the simplest before we move on to the next steps.

 

[tmo]

Re: confusing problem from today...

thanks very much for your patience and the detailed replies. I did try the witness mark test with a sharpie mark on the prop hub and the shaft and after turning them together (in gear) they remained lined up. is it still possibly a spun hub that only affects higher speeds? as I said the problem only came up when I tried to get up to speed?

I am hoping to get out on the water tomorrow with my old OEM prop with its own hub and see if that works?


again thanks, any other suggested investigations will be welcomed.

 

[Silvertip]

Re: confusing problem from today...

You need to perform that witness mark test in water under power.

 

[tmo]

Re: confusing problem from today...

right thanks.

hopefully will be able to get out tomorrow night to test it.

 

[MikDee]

Re: confusing problem from today...

IMO, it could be a bad, or worn out, engine coupler.

 

[QC]

Re: confusing problem from today...

I am not sure what he did wrong. Reread please, he said, "I did try the witness mark test with a sharpie mark on the prop hub and the shaft and after turning them together (in gear) they remained lined up". He has also said that he can spin the propeller by hand, in gear. Seems that he has elimintaed the hub to me Why would he need to redo this testing in the water?

I agree with MikDee, sounds like a possible coupler failure . . . Needs to be moved to the I/O section . . .

 

[tmo]

Re: confusing problem from today...

AS far as coupler failure, could someone educate me on the best way to diagnose it? The boat was working until I cnaged the prop, one thing I have not mentioned that I changed the prop after an incident with a rock where there was not a severe but nevertheless an impact with lower unit...

 

[bhammer]

Re: confusing problem from today...

Run the witness test in water. When you are doing it, stick your nose in the bilge real good too and see if you smell any burnt rubber. This is usually the sign of a failing / failed coupler.

My next guess would be the coupler, but now that you saw you had an impact, that changes the odds on what could be wrong.

 

[QC]

Re: confusing problem from today...

I have the same question I have above. If he can spin the prop by hand IN GEAR both directions and the prop and propshaft stay aligned why does he need to retest this in the water? Because we said so? Or because he will gain some valuable information when he is only going 5 MPH and his engine is humming along? Yes, burnt rubber will help confirm a coupler, but it sounds to me like this drive already has to come off . . .

tmo, there is a round donut type thing deal that attaches to your engine at the flywheel. The input shaft for the drive goes into that donut which is very similar to the splines on your output shaft (propshaft). This round thing also has a rubber "hub" that helps isolate the engine from the drive if there is some major problem. It also "cushions" (dampens) any shocks between the two. It is THE connection between the drive and the engine . . . Exactly the same as a rubber prop hub, but 100% completely different

 

[tmo]

Re: confusing problem from today...

thanks, I will visually insepect the engine compartment for shards of rubber or metal from the coupling before venturing out, is this reasonable?

 

[Bondo]

Re: confusing problem from today...

one thing I have not mentioned that I changed the prop after an incident with a rock where there was not a severe but nevertheless an impact with lower unit...

Ayuh,.....

Before you go Anywhere,.....
Pull the Drain Plug out of the outdrive,......
I'm bettin' you'll find Shiney Metal in the oil......
It should take more than a few drops to know....

You shouldn't be able to turn the prop by Hand,....
And,...
Your boat is almost To New to have a Coupler Issue.....

 

[tmo]

Re: confusing problem from today...

hi guys,

I did get a chance to get out yesterday and test out few things. The results were great but confusing. I started out with the original OEM prop with its own hub and everything seemed fine, no problem accelerating to speed etc... I then installed the problem prop with the witness marks and went for a test, surprisingly the boat performed fine with that one as well, and marks line up...

Im at a bit of a loss as to what happened the other day, the only thing that I can tell you about that day was that some of the area I was in was very weedy, not sure if that could have caused a problem, I tried to remove the weeds each time I passed through them but it was difficult... the only other thing I canthink of is that I didnt tighten the prop nut enough?

in any case I really appreciate all the help from this forum, you guys are really doing a real service to us novice boat owners out there...

 

[MikDee]

Re: confusing problem from today...

AHA! Seaweed, I'm well familiar with it! and just how did you try to remove it?
You must slow down, shift into reverse, then gun it a bit, then slow down, & go back into forward, & gun it some, all in one smooth, swift, moment. That should unwind, & remove it.