Alpha One Flywheel Coupling Failure?

[john j 80 viking]

Same boat different problem
26' Scorpion (2) 260hp Alpha Ones

Boat accelerates normally, but when full throttle is applied and boat is near top speed, the starboard engine over revs and the boat falls off to the right. The props are the newer Marage Plus w/ the removable plastic hub. I inspected the hub and did find cracks radiating outward from the 4 large splines from the bronze center part, but there is no obvious evidence of proppeller hub slip.

Does this point to the coupling?
Is this a common problem?
Is there any way to test the coupling before I yank out the motor?

Thanks, John

[flabum1017]

pull the drive, it will be obvious it it's the splines. Also, if you let it keep revving for 30 seconds or more, if it's the rubber part of the coupler, you will smell burning rubber in the engine room and some smoke.

[john j 80 viking]

pull the drive, it will be obvious it it's the splines. Also, if you let it keep revving for 30 seconds or more, if it's the rubber part of the coupler, you will smell burning rubber in the engine room and some smoke.

I'll try that, thanks again

[Instigator]

If it is, check engine alignment. If severe, this will eat couplers.
When you go to re-intsall drive if the input shaft does not want to easily engage the coupler splines the motor is out of align.
If the splines were gone you'd be done.

[flabum1017]

If it is, check engine alignment. If severe, this will eat couplers.
When you go to re-intsall drive if the input shaft does not want to easily engage the coupler splines the motor is out of align.
If the splines were gone you'd be done.

If the splines went, the boat would not move any more, if the rubber part is slipping, it would "re-grip" adter it cooled some. Sometimes, if there is visual access, you can see melted rubber around the coupler socket where it's glued to the rubber. If you can get a visual from above in the engine compartment, you may see it , if you see aluminum dust, then it's the splines. If you run that motor only under a load (trying to get on plane) by itself (other motor off), it should break loose easier.... once it breaks loose, let it rev at 4500 for 30 seconds then go smell for burnt rubber in the engine compartment.if there's no smell, then the problem is probablt the prop hub.

[john j 80 viking]

If the splines were gone you'd be done.

Good point, also I've had this boat since 2005 and have had the drives off many times, they slip right back in.

I'm gonna try the smoke test before I pull the drives. Are those things expensive?

[bigblockdock]

I agree with FLABUM 1017, once your splines are gone, you do not go anywhere and if you have the earlier model drives with the water pumps in the outdrives, engine temp will rise when the driveshaft is no longer being turned by the motor.. I've never seen splines slip at high speed and work good at lower speeds. If the coupler rubber let loose at high speed you would most likely smell the burning rubber in seconds. It's a smell you won't forget. Alignment problems that cause coupling failure mostly occur after engine installation when an alignment tool is not used. I think you have a bad prop hub . switch hubs in the props, from one prop to the other and see what happens. The problem will switch to the opposite motor if its the hub. Eliminate the hub first. Maybe its a cavatation problem possibly from something that got hung up on the outdrive while underway and then dropped off.