Stern driven water pump conversion to engine driven water pump

[BRANDON43]

I own a 2004 Searay 280 Dancer. In a couple months I will be putting her on the dry dock for maintenance. During this time, I will be removing both Mercruiser outdrives and have them repainted, replace both u-joints, oil seals and check for bent shafts. I was also thinking about adding an engine driven water pump. Presently the cooling water comes from the outdrives. Can the impellers be removed in the outdrives? and install allow the new engine driven water pump to pull water from the outdrive. The boat does not have an extra seacock.



Has anyone had any luck with this?

 

[Ididntdoit]

you could do it with Mercruiser parts.....but I would use crank mounted pumps - you get a better designed pump and easier access for impeller changes......I would also add seacocks - never have to worry about drive cooling restrictions and get a way to shut off the water coming into your boat....just be sure to cut the feed hose on the drive so it still gets the flow through cooling......if this sounds like too much work, its not a problem drawing from the outdrive....

 

[NorCal Boater]

Mercruiser actually has the parts available to do this. My 1985 Cobalt has the engine mounted in the middle of the boat, not the stern, and has a drive shaft back to the Alpha drive. Merc called this a Jackshaft model. I have an engine-driven water pump through the bottom of the hull like an inboard. All of the plugs and special parts to block off the stern drive pump water supply are there. However, I was always told to keep the pump in the stern drive as it pushes cooling water to the upper gear case so I've always maintained that pump. Seems like a drive shower would do the same thing. I do not have the hose that goes through the upper unit through to gimbal housing and to the motor. There is a special block-off part that replaces the copper tube that goes through the gimbal housing.

Go to one of the Mercruiser parts suppliers on line and do a search for "Jackshaft Model"

 

[Stee6043]

Would this change cause you to be less likely to maintain your outdrives overall? If so...don't do it!

I've been deeply scarred by an Alpha drive in a past life. It was a horribly abusive relationship.

 

[BillK2632]

I would question the economics of doing this - unless you have something else going on, those pumps are in the $300-$400 range plus any other stuff to covert it - belts hoses etc.. The Merc engine mounted pumps are not really known to have the service interval of an Alpha I Gen II pump (the old Alpha I pump is a different story). The engine mounted pumps use a small impeller and run at the engine RPM, the Alpha I Gen II pump runs at the drive speed which is slower than the engine - depending on the drive ratio. The Alpha I impeller is much larger than the Bravo / Engine pump and they tend to last longer. I usually get 3yrs out of mine and they still look good - never had one fail. I have heard of people going much longer. Having the pump in the outdrive is a bad design from a service standpoint, but otherwise the Alpha I Gen II pump, and drive for that matter is solid. Even the engine mounted pumps can be a real chore depending on the boat and installation. I personally would not do it.

 

[dpmulvey]

Agree with NorCal. Thru hull, strainer, crank pump and drive shower. Technically, I don't know about the water cooling the gears from the inside. However, a friend had a pair of mercs on the back of his go fast and prior to drive showers, you could have fried an egg on the upper unit after even a mild run of say 40 knots.

 

[BRANDON43]

Thanks for all the input guys. The upgrade was for the ease of maintenance on the impeller.

 

[mnm99]

I personally wouldn't bypass the drive. It's used to cool it also. They get HOT. I built a drive shower for my BIII but never got to use it before I sold it.

 

[BRANDON43]

I totally agree. I would not bypass the outdrive, I was thinking of pulling the water from the outdrive in lieu of installing a seacock.

thanks,