Transmission Won't Move Boat

[lively]

well if the clutch pack is locked solid in velvet drive it might cause that problem .. but i would check fluid and stick you nose around the trans ... maybe a bearing locked up on trans ?

[Century63]

If the clutch pack is locked solid in the velvet drive, why would it run the prop both forward and reverse while sitting on the trailer. The fluid is fine. The back bearing where the shaft comes out the back (hub) again, is not locked up when boat on the trailer, runs then. Only does this when the trans needs to push the weight of the boat through the water.

[mr.jrc]

A couple of things... first, if you engaged the prop when out of the water, you have already damaged the cutlass bearing in the prop shaft support, this is just a rubber bushing encased in brass that supports the prop shaft. It relies on water flow to keep the rubber from melting.

Sounds like excessive slippage since you can engage fwd and reverse and get the prop to spin. You can verify this by using a strobe tachometer when running to see what the difference in RPM's is from the transmission output to the harmonic balancer on the front on the crank.

[csuggs]

Mr. jrc is right about the bearing - you'll need to replace that when this is all done. A couple of things . . . .

You DO have water running to the motor when you are running it on the trailer, right? Just checking.

Check to see if the prop shaft turns easily by hand when in neutral and boat on the trailer. Then check the same thing when in the water . . . it might be a stretch, but I know that the alignment of the shaft can change when the boat is floating, as opposed to being supported by the trailer, especially if there are structural issues. If the shaft is difficult to turn when the boat is floating, then that could be causing the motor to "load-up".

It doesn't sound like a transmission slipping problem to me if I'm understanding the symptoms correctly.

Clint

[DKJBama92Mariah]

Mr. jrc is right about the bearing - you'll need to replace that when this is all done. A couple of things . . . .

You DO have water running to the motor when you are running it on the trailer, right? Just checking.

Check to see if the prop shaft turns easily by hand when in neutral and boat on the trailer. Then check the same thing when in the water . . . it might be a stretch, but I know that the alignment of the shaft can change when the boat is floating, as opposed to being supported by the trailer, especially if there are structural issues. If the shaft is difficult to turn when the boat is floating, then that could be causing the motor to "load-up".

It doesn't sound like a transmission slipping problem to me if I'm understanding the symptoms correctly.

Clint

I agree 100%. with JRC and Clint's posts. When a transmission slips, the engine revs up, it doesn't lug down. I think it's either an alignment/binding issue as Clint suggests or an engine issue.

Exactly how long did you run the boat in gear on the trailer?

How fast did you rev it in gear when on the trailer?

When the boat is in the water, how many RPMs is it turning when it is straining as you say?

[csuggs]

Here's another angle I just thought about. When you are running the boat on the trailer I imagine you have the engine cover raised. Is the cover closed when in the water? If so, could it be that your fresh air intakes are somehow blocked, allowing just enough air to let the engine idle but not rev - thus choking the engine?

[Century63]

Hey guys, thanks for all the ideas. When I have run the engine with the boat on the trailer I have water running through the engine. Also, I have water running on the shaft and where it goes through the strut under the boat to make sure it is lubricated. The is a 63 Century Resorter and the motor cover has a lid on the top of it which is open when I put the boat in the lake to see how everything is running. The load on the engine is significant with the throttle pulled out and the rpm attempting to climb but rpm does not get out of the teens. With the boat now wanting to move I throttle it down and take out of gear. When the boat is on the trailer and the throttle is pulled (or in neutral when in the water) the rpm will jump to 5000. I do not hold it there for any length of time. Just wanting to see if it is smooth (no miss or anything like that). I probably ran the boat in forward for maybe 5 seconds and then the same in reverse to see if it shifted and moved in those directions. For those of you who think this is an engine issue, what would be your ideas on that issue. Remember, it has been totally tuned and the heads have been completely gone through. Also, it ran great when put away, never moved when put in the next year, even though it ran on the trailer without issue. Again, thanks for the help. I am in AZ right now and the boat is in IA. Will start looking into some of the ideas when i get back home. Thank goodness for the old Supra Pirata to keep the vacation going.

[mr.jrc]

So no problem getting high rpms (5000) with no load, but peaks out in the teens (say 1800 rpm) in the water in motion. Is that right?
Like Clint said, you might be absorbing the energy by a bound up prop/alignment, that would create alot of friction and quickly cause problems in bearing surfaces or the shaft log. (Be careful running the engine at high rpm unloaded)

The way i look at it you have one of two issues, you either are or are not producing the right amount of energy. The engine power is is being absorbed before reaching the prop or you are just not producing the power. I would look into the power producing side.. you could have a fuel or air flow restriction, allowing enough energy to run the engine at full rpm, no load, but peak out and a lower rpm at full load. (your case when in the water).

[Century63]

Thanks for all of the ideas. I will be checking these issues you have mentioned this summer. Will let you all know what I find out. Again, thanks for all the input from everyone.

[DAFF]

I would make sure the prop is free to move in neutral, reverse and forward. From what you are describing it sounds almost like a dead head fluid restriction.