Alpha 1 help...
 

Saturday was nice and pretty and from here weather looks good. So I went and got the Wellcraft Nova out changed engine oils and gave it a good cleaning and stuff like that. Fired it up on the hose at home zero issues all seemed great! Decided to go drop her in the lake for a shake down run.... Welllllll I barely get out of the no wake zone get the boat up and out on plane everything seemed perfect. Suddenly drive just completely quit pulling. And I had to ease back in on one. Here are a couple of things I have investigated on to narrow it down.

Quit pumping water.
Shift cables all seem to be fine.
You put in in either forward or reverse it locks up like it should while on the trailer but you can spin the prop still if you give it some force (unlike the other side that is still good ) if you try to turn it while in gear you cannot at all.
No rubber smell or anything like that for it to be the rubber coupler?
Engine runs just fine still.
I think something broke.
Gonna try to take lower off this week maybe investigate a little more.
Possible spun prop?
Any suggestions would be great
Alpha one Gen 1 1.5 gears (260 mercruiser)

when in gear is the prop with the propshaft spinning or just the prop spinning ???

easy to check whats spinning - mark your spots with nail polish - mark the end of the propshaft continue over the hub then on to the prop itself. After turning the prop with the drive in gear - see if your marks line up - if not a spun hub.

Most likely you need the complete water pump kit, Replace all that - hence not pumping water.

Just doing the impeller only is a waste of time. Wear plate grooved and I bet the small plastic housing is melted someplace.

If it quit pulling and quit pumping at the same time ,sounds like coupler...It could be stripped splines, which you won't smell. If you can see behind the motor the input shaft ..Have someone turn the drive while in gear and see if the shaft going into coupler turns....

You have to ask then as no mentioned - when out on the water did the engine overheat right after the drive problem ? I would agree then about the coupler if both happened at almost sametime - the drive problem first and then within 30 sec later the engine temp sky rocketed.

Agree watch the driveshaft while someone turns the prop in gear. Those are the 2 test I would do first as in the replies here.

Honestly I do not know in which order they happened it almost seems like both things happend at exactly the same time ... No go and hot

When it's in forward gear and on the trailer I can spin the prop ccw (where it should be locked) but I isn't necessarily easy to turn it. But it does turn. And the other side does as it should.

If it wasn' for the heat I would say spun prop...but no go and hot points to the coupler. If it's original it's way over due.

Pull it out of the garage and fire it up on the hose then put it in gear... if it sounds like the garbage disposal, its probably yhr drive...if it doesnt, its probably the coupler.. To check the prop just pull it off and look

It's the gimbal bearing locking up.

The vertical shaft could have broke resulting in loss of propulsion and water pump. The older vertical shafts had an o-ring groove in them and were known to break under heavy load (planing off)