Question: Dual Water Intake for 4.3 Merc Alpha One Outdrive

ModernRifle

Cadet
Joined
Jul 16, 2013
Messages
6
Overview: Questions regarding a dual intake water system that was modified.

Facts:
2006 4.3 Carb Mercruiser with closed water heat exchanger
Alpha One (Gen 2 ) outdrive
Manufacturer Trophy Bayliner with Dual Water Intake Sticker.
2008 or so... Overheating.. Dealer couldn't fix. Their Party made operable*
(* It appears it is now a single intake using the original through hull to engine pump)
Alpha One hose appears to be cut.. not apparent water intake through the lower unit to engine...
or any other use of Alpha One lower unit intake....

Questions:
1. Does an alpha one outdrive require water cooling or is it sufficient to be immersed and lubricated?
2. Is there a way to reconnect the Alpha Impeller Water Pump system to be useful.

I find very little information on this "Dual intake system" which appears to have been both a through hull to a Bravo system and an Alpha Outdrive Intake that joined the main system.

Glenn
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
49,585
first, is this a converted heat-exchanger installation?

If yes, then is this a full system or half system?. if half system, you only need the raw water pump in the leg. if full, you need to add a thru-hull, run the bravo pump, and the alpha pump just keeps the drive cool (you cut the hose)

if no heat exchanger, then you only need the raw water pump in the leg
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
1. Does an alpha one outdrive require water cooling or is it sufficient to be immersed and lubricated?

What SHOULD have happened (on closed cooling installation) is the water hose inside the bell housing is cut. That allows the pump in the drive to still operate and pump water through the drive (some cooling to the drive is required). A blank off plate should be installed where the water hose comes through the gimbal housing. If they went 'cheap' (as most installers do :facepalm:) they will have just plugged the hose in the inside of the transom.

2. Is there a way to reconnect the Alpha Impeller Water Pump system to be useful....

If you have the genuine Merc closed cooling kit (which also cools the exhaust manifolds), then you need the engine driven pump (and through hull pick-up). The pump in the drive is insufficient to provide the flow the closed cooling system needs.

Chris.....
 

ModernRifle

Cadet
Joined
Jul 16, 2013
Messages
6
Thank you Scott and Chris.
.
My Trophy is stock and I do have the bravo style through hull inlet for the engines full closed system heat exchanger.
.
It looks and works good...
.
My Alpha outdrive does have the hose cut... and am still checking that the impeller is working..
.
When I run it in the yard, I use the plumber plunger style water supply to the through hull and the ear muff style on the outdrive... Forced water always seems to run through it, but I'll have to get on the water to see if the impeller is still working... (or maybe a livestock tank full of water???)

Thank you.. I did find that some lower units are described as dual intake, but what you both described is what I see to have... I'm less alarmed now with the 'cut' hose...

Thanks
 
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