Merc Alpha cooling

I'm repowering my houseboat with a Merc 4.3 EFI. The new motor I bought is a Bravo set up. I'm going with an Alpha Outdrive. I have switched the throttle plate and figured out the control module and wiring. Now I need to adapt the cooling. The Bravo motor has a seawater pump, the Alpha outdrive uses it's impeller to pump water to the motor. What I'm wondering is if I can bypass the the Alpha outdrive intake and use the Bravo seawater pump to suck fresh water through the hull direct to the motor and exhaust back through the outdrive. This would be very handy to be able to service the bravo pump inside the engine pod and not have to mess with the outdrive impeller since the boat has to be hauled out to work on the outdrive, about $700.00 for the haul out.
Thank You for your replies,
Darrell

jeez thats alot for a haul out they charge 200 here. What you have a gen 2?

Best approach is to use a thru-hull and a strainer to feed water to the bravo pump. You'll have to 'dump' the alpha pump output, probably back thru the exhaust...I'll let others (with the Tee shirt) provide those details.

All though I have not seen or done this before,

I would suggest that you remove the outdrive impeller, if you have the thru transom hose from the outdrive put a plug in it and hose clamp it so no water can make its way into engine bay.

Good luck.

Allthough the alpha gen II water pump would be good for several years if run in fresh water...

if he pulls the outdrive impeller, doesn't he lose the cooling of the upper drive, whne up on plane?

Well if he is not using the water from the outdrive, what is he going to do with it?

He would need to put a TEE or something into the exhaust to allow water flow.

Also he would still be facing the same issue of maintenance down the road so why not just use it as intended????.

This is why the alpha and bravo systems do not mix well. It takes some careful thought and set up and if done some good plumbing to keep everything cool.

makomark said:

if he pulls the outdrive impeller, doesn't he lose the cooling of the upper drive, whne up on plane?

Click to expand...

Yes, that is correct! Since there is no exchange of gear oil between the Alpha lower unit and upper unit, the sea water is what provides the upper unit cooling.
Bottom line, you can't simply eliminate this pump..... nor can you defer maintenance on the Alpha impeller in this scenario!

You also have the issue of the Bravo engine set-up regarding it not having the linkage for the Dog Clutch Alpha drive Shift Interrupt system..... of which is absolutely necessary for Dog Clutch shifting back to neutral!

Back to the Alpha pump:
This supply can be ported over-board, or it can be "T'd" into the Bravo engine mounted pump inlet.
Do not dump this into the exhaust flow directly! Bring it in through the engine mounted sea water pump! IMO.

I've done this to an Alpha drive engine whereby the Closed Cooling system was a Full System and used an engine mounted sea water pump also.

Your simplest solution may be to use the Alpha pump only, and abandon the engine mounted pump.... of which seems counter intuitive to me!

I would send the alpha pump discharge to the suction of the bravo pump. Degradation of either pump would not result in a total loss of cooling to either the engine or the sterndrive, and you would have some indication (by increase in engine running temp) when either of the pumps starts to wear.

Ayuh,... Just cut the transom Hose on the Alpha,+ Plug the boat side...

It'll spray all over the upper for cooling...
And, Yes, the alpha pump will Still need to be serviced,...
The pump body holds the oil in the lower...

The impellers last along time with proper use and care, i let mine go 4 or so years, just replaced em (they were fine).

the key i think it frequent use, don't let them dry out, what your temps closely for change from normal.

Any find yard with a smaller CLUB to do your haulout!!!