Alpha I water pump conversion?

SCORPIO

SCORPIO

Well-Known Member
Apr 7, 2008
2,743
Delaware
Boat Info
1989 300 DA
Engines
Twin 5.7 Merc Alpha I
Is it possible to delete the water pump in the outdrive leg of an Alpha I gen I and install engine driven raw water pumps? Its time to do waterpumps again and I hate taking the drive all apart to do them. My neighbor has Bravos on his Scarab and I was looking at his setup, sweet, ram scoops to the strainers, then to the raw water pump and then he even eliminated his circulating pumps and has a 'cross over feed' that is just piping in place of the engine circulator. Seeing that got me thinking and wondering if I could do something similar, minus the cross over stuff, I'm not looking to free up two horsepower for more speed like he is.
I already have two thru hulls I could use as pickup points, one is for the macerator dishcarge, which I've never used and don't plan to, in front of the port engine and a blanked off one in front of the starboard engine that would be for the generator my boat doesn't have.

So what do the experts say, waste of time or a good idea or impossible?
 
Chris, I have a closed cooling system on mine, and run Jabsco raw water pumps. You still need to run the pumps in the drives however, due to the fact that they are needed to cool the drives. I have heard some say you dont need them, but my best friend....Merc cert. mechanic says I'll overheat the drives if I dont run them., Dave
 
Thats what I was afraid of Dave. So how is the water fed from the drive in your setup? If the pump is pumping water where is it going if not thru you heat exchanger? A pic or diagram of your setup would be great to help me figure this out. I'd love to find a set of Bravos cheap along with transom housings and then I could eliminate the outdrive pump completely. However short of winning the lottery I don't see that mod happening lol.
 
On the models with closed cooling, the hose from the transom bell, to the transom assy. is simply not installed, and there is a block off plate on the inner transom assy. where the white nylon elbow usually is, allowing the water to just pass through the drive and right back out. Cant get a photo as that area is non accessable and there is nothing to show.
SCORPIO said:
Thats what I was afraid of Dave. So how is the water fed from the drive in your setup? If the pump is pumping water where is it going if not thru you heat exchanger? A pic or diagram of your setup would be great to help me figure this out. I'd love to find a set of Bravos cheap along with transom housings and then I could eliminate the outdrive pump completely. However short of winning the lottery I don't see that mod happening lol.
Click to expand...
 
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That makes sense to me Dave thanks, don't need a pic. I would like to see a pic of your engine mounted water pumps, specifically how they are mounted.
Thanks
 
I'm in the boat today servicing the gennie so I'll shoot you some pics.
 
from what i know of the Alpha and Bravo systems

why couldn't you hook it up like a bravo?

pull the water through the drive to your new pump and back to the cooler where the hose from the transom tied in now.

pull the pump guts from the alpha drive and go.

scorpio;
i did the swap from alpha to bravo on our 230 a couple of yeas ago. if you get a chance, it really make a nice adaptation.
pretty straight forward and was able to us all merc parts so will be able to get parts and repairs if needed.
i did use a B lll but that was over kill on this boat. a B l would have worked as well. in for a peeny in for a pound......

good luck

will look and see if i have any pix on the hose placement i used on the bravo transom assembly
 
Subscribed! I wouldn't mind making my system like this as well!
 
hose from sea water pump to oil cooler. only change is new hose from sea water pump [the one that curls back and under the motor]. this a factory merc hose and pump ect. no matter how you get the pump installed you can tie in to system here with out changing any thing else past her


bravo transom assembly with water inlet just above gimbal bearing hole plastic ell not yet installed



alpha transom. water inlet is white nylon stub sticking out above gimble hole and under steering cable.

this could be the down fall in this swap as the bravo trans ass use 1 1/4" i d hose
 
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even if you cant pull fresh water through the drive, losing that bit of cooling, every thing else stays the same in the cooling system. i think drive shower would cover what cooling you would lose there. if that was a concern.

i think scoripo will ment he would run a separate pump for each motor?
 
I'm not knocking anyone's ambition - far from it... but why change? I mean, when you consider there's a decent amount of cost and time/effort put into this and that to change an Alpha impeller only takes an hour (and no contortionism is needed!), I don't really see the benefit. Besides, look at the cost difference down the road... both impeller pricing and housing pricing is higher with the Bravo setup.

It's an interesting thread - just wanted to ask a question that was weighing on me.

That being said, I would definitely go with the Jabsco unit over the Merc pump.
 
There are a couple reasons I wanted to do the conversion:
1 - It would allow boats left in the water with a way to flush the engines. I do not know of any way to do this with an ALpha that is sitting in the water.
2 - Alpha pumps are easy and fairly cheap to change, granted the boat is on a trailer. Not so easy when the pump gives out in the middle of the bay, or you have to pay for a haul out. Luckily I do have a trailer for my 280.
3 - Reliability - I actually had to change an impeller on the water in my Wellcraft with the volvo. It saved the trip.
Mike
 
Good points, Mike. Serviceability on the water is a key one.

You're right, it's pretty hard to get a flushette on the drive while the boat is in the water. On some boats it's not too hard (attach the flushette to a pole and/or tilt the drive up for better access), on others it's either very inconvenient or darned near impossible.
 
Lazy Daze said:
Good points, Mike. Serviceability on the water is a key one.

You're right, it's pretty hard to get a flushette on the drive while the boat is in the water. On some boats it's not too hard (attach the flushette to a pole and/or tilt the drive up for better access), on others it's either very inconvenient or darned near impossible.
Click to expand...

Not to steal the thread but I still find it hard to belive they haven't come up with a quick flushing system for the Alpha's. My previous boats were all outboards (impeller in the lower unit) and all I did was screw a hose in the back of the motor (near the power head) and turn on the water. Why is the Alpha system so different than an outboard? My boat is lift kept and I use the earmuffs but it's a PITA!
 
I keep my boat in a slip for the season and I don't have a trailer so serviceability is one consideration for me. I also hate pulling the drive apart everytime I need to change impellers, kind of like haveing to drop and oil pan to change and oil filter.
 
You can install a crank mounted raw water pump, and pull the water in from a strainer that has to be installed. You ythen cut the water inlet from the outdrive and allow the water pump to pump the sea water onto the transom. You then have to plug the inlet water hose so that you do not get water into the bildge. Now you have the frive being cooled, and the impeller is serviceable because it is in front of the engine. You then can cut a cut off into the feed to the engine so that you can attach a garden hose to fresh water flush the engine. I had a 280 Say with T5.7 in which I considered this approach. This is the pump http://www.amazon.com/Water-Pump-Pleasurecraft-Sierra-Inc/dp/B000XBHK90
 
Chris, I forgot to take those pics of the pumps for you today, but when you see where they are, you will want to do your impeller changes on the drives on the bench instead of pulling raw water pumps apart in the lowest part of the bilge in the front of the motors. I will get you those pics tomorrow. I have to do both drive impellers and both raw water pump impellers this year. (Jabsco)
 
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