Tip- Air Lock in an Alpha Gen 2

[JoLin]

This was a new one on me, and might help someone else. Had water pump service (along with some other stuff) done on my Alphas a few weeeks back, while I was replacing ALL the old cooling hoses on one engine. When I fianlly got around to starting it, the temp shot up to 200 deg. I shut it down and went back over all the work I'd done but couldn't find anything wrong.

Pulled the water intake hose off the t-stat housing, started the engine, and there was no water coming up from the drive. I called a mechanic friend who told me that an Alpha could occasionally develop an air lock and not be able to pump water. The fix (rightly or wrongly) involved pulling the lower unit again.

Another friend who was with me at the time suggested backflushing the hose in case there was a 'blockage or something' causing the issue. He went down next to the drive while I stuffed a garden hose into the cooling hose. Soon as we turned on the water, he called up 'I hear air coming out' and a couple seconds later 'here comes the water'. I put the muffs back on, fired up the engine and it was pumping water like a champ. Reconnected the cooling hose and temp slowly rose to 140 and stayed there.

 

[Grub54891]

Hmmm.. Never had one airlock on me. I think I'd check to make sure the impeller key is in place,it will work on the hose but not on the lake if the key is not there.

 

[JoLin]

The key is there. I saw both drives being reassembled. And, the water pump DIDN'T work on the hose until I forced the air out with a blast from the garden hose. It was probably an anomoly having to do with replacing all the hoses at the same time. The hose run from the outdrive pickup runs goes down to the PS cooler, then back up to the t-stat housing. I can conceptually picture an air bubble somewhere in that run. The mechanic I called told me that the air lock situation is unusual, and it's one of those things that can drive you nuts trying to figure out and fix.

Just throwing it out there as a possible fix for anyone with a similar issue.

 

[JustJason]

That's usually a sign that either the base plate gasket is torn. Or there is scratches on the base plate or pump housing. Basically whats going on is the impeller didn't "prime" when it was dry and had the muffs on the water pickups, when it should have.

 

[airshot]

I have seen that on autos many times, but on an I/O would be hard to believe due to the fact that pressure from the hose (muffs) or pressure from being submerged in water from the lake would force the air above the water pump. I have to agree here I would open it up and do some checking before you venture to far.

 

[Bondo]

Ayuh,.... I'm wonderin' whether there's an ole impeller fin bouncin' 'round in there somewhere,...

Coulda be pushed into a blockin' position the 1st time, 'n knocked outa the way with the back-flush,....

More believable than an air-lock in an open system,.....

 

[JoLin]

Okay, you guys are right, and I was wrong. It overheated again this morning. I just left a message for the mechanic who serviced the drives. I'll let you know what I find out.

 

[JoLin]

I promised I'd report back after the mechanic came. Though the answer sounds nutty, I did what he suggested and I've been running the motor for 2 days without any issues whatsoever.

He looked over my setup, and said he doubted there was an issue with the drive (he put in all new parts), but the water supply to the drive was suspect. I was using one of those super-stretch hoses they advertise on TV, with a pair of rectangular muffs. First, he told me the round muffs seal better, and second, the hose appeared to be putting a lot of pressure on the muff and pulling it slightly away from the drive. The reason I wasn't suffering the same on the port drive was that it's just a little closer to the house, and the hose wasn't exerting the same pressure on it.

We did a couple of test runs with his muffs and everything was fine. I went out and bought round muffs and screwed a regular hose extension to the super hose. Haven't had a bit of trouble since.

If anything changes I'll post again, but it seems to be the answer.

 

[Grub54891]

I have one of them type of hoses,they shrink/collapse when they free flow. I'd suspect it caused a restriction.
I've never had a problem with round or square muffs,it's just that some work better on different drives,that's why I have both anyway.