Is the Water Pump in the Outdrive Necessary?
 

My Checkmate has a unique cooling system, it has a closed loop system fed by a bravo style water pump. The alpha outdrive also has a pump, but it just dumps right against the transom, right at the gimbal. When I run it on the trailer I use 2 hoses, one to the bravo pump, and one to earmuffs on the outdrive. When I winterized it, I accidentally ran it for about 45 seconds without water going to the outdrive, burning up the impeller in the drive. I don't want to replace it becuase I don't like all that high pressure water shooting against the transom and bellows. I do run a Simrek drive shower. Do I need the pump in the drive?

Where is the pickup for the Bravo pump at? Is it a thru-hull fitting?

That is a unique setup indeed...

Correct, it uses a thru hull fitting with a brass cup. I have neither seen nor heard of a similar setup.

You need to run water through the drive to help cool it, but I think the pressure going into the intake holes at speed will take care of it. I had an external p/u for my bravo and it spit out a good amount of water out the dump from just the pressure.

I would get the pieces of the old impeller out though.

Griff,
Are you saying a new housing without an impeller might be enough?

Hey Pete,

This is just a guess here, I have never seen a set up like yours before. But, I would think that your drive needs an impeller to move enough water to keep the drive cool. Griff said the forward motion of you hull should be enough, but I tend to dissagree. My basis is that your Alpha has side water pick ups. I dont know how much water can get pushed through those, as compared to forward facing pick ups.

Where should I route that stupid hose? I am not sure where I can route the hose so it isn't shooting against the transom. I don't think there is enough room to route it between the little space near the gimbal, I think it would get pinched by the drive swinging through its range of motion. I was thinking about maybe drilling some holes in the plastic pump housing to relieve some water pressure, and maybe even trimming off some of the impeller blades as well. I don't know if doing the latter would make it no longer function.

Do you know you burnt up the drive impeller or are you just assuming from the dry start? You could always try running it and hang off the back at speed to see if you are getting less water dumping from the drive pickup before you replace it. But then again if you pull the lower to pull the burnt one out, why not just go ahead and throw a new one in there?

We had an old Checkmate with a Merc One drive, or whatever the Alpha was before they called it the Alpha, that needed a lower pump for years, the engine would get hot until we got up on plane, then it would cool down once we cruised for a little bit. It was like this from the time I was 15 until I was 20 when I could finally afford to pay to get it fixed. Granted we only used the boat 3-4 times a year but still wasn't very smart. The dumb **** you do when you're young...

When the pump was good, I could see water splashing out from that little hose when it was idling on the trailer. I know no longer see water splashing out, but that is only at idle, I don't know what it is doing at speed or rpm's. I think I will try doing a little recon when it is up on plane, becuase if it is pumping some water at speed that would be great, and hopefully it wouldn't be flowing like a fire hose, but just enough to cool the drive...

I would not run it for any extended time cruising or at WOT w/o an impeller in the Alpha. The upper case is designed to be internally cooled by the water going thru it. The side pickups are not gong to let enough water in and your drive shower is only spraying the top cap. I believe doing that and running it hard could result in drive failure. Your best bet is to throw in a new water pump kit or at least an impeller. IF you ran it for 45 secs with no water on a stock impeller it's gone or at least compromised. I've seen them run dry for 15 secs and they were smoked. Imagine dry rubber rubbing a metal insert for 45 secs. Alot of friction there.