Running engine without stern drive attached?

[Fishermark]

I am installing a new 5.7 liter Mercruiser engine in my boat. It has a 1988 first gen Alpha 1 outdrive. I am bypassing the water pump in the outdrive with an 1.25" thru hull fitting and engine mounted raw water pump. I have the engine installed now, but not the stern drive yet. It is okay to run the engine without the stern drive attached?<br /><br />On a related note, I am surprized at the difference of opinions on whether the water pump in the outdrive is needed now or not. Some say yes, it is needed to cool the outdrive. Just cut the hose in the bell housing and plug the hole in the transom and you are good to go. (This is what I have decided to do). Others say, (and these are Mercruiser mechanics), that the water pump is not needed at all. Simply take out the impeller. The outdrive will stay cool simply being in the water. Thoughts either way?

 

[crazy charlie]

Re: Running engine without stern drive attached?

You will still need to run water to the new pump you installed in order to run the motor.The impeller in the o/d runs water to the engine.If you are getting the water from somewhere else as you are ,then you dont need the pump in the o/d.Personally,I would leave it functioning and have it enter the usual way and exit through a thru hull.Put a switchable valve in line and you will have emergency cooling if the pump you installed fails.Charlie

 

[Bondo]

Re: Running engine without stern drive attached?

" It is okay to run the engine without the stern drive attached?" <br /><br />Sure... Why Not.....<br />Just make sure you're Feeding All the proper Fluids, in the Right Places.....<br /><br />If you're running the Bravo style raw water pump, there's No Reason What So Ever to leave the impeller in the Alpha1......<br />Nothing in the outdrive is cooled by Pumped Water... The water flows from the impeller up through a copper pipe Inside the Exhaust passage to the Gimbal.... No Cooling There.....<br />Listen to the fella's with their fingers inside them....<br /> (and these are Mercruiser mechanics),

 

[Fishermark]

Re: Running engine without stern drive attached?

Listen to the fella's with their fingers inside them....<br />I should note that the ones who mentioned needing the impeller and the water flowing through the outdrive are Mercruiser mechanics as well. What's funny is that both sides are pretty adamant that they are right. I figure it is not a problem to leave the impeller in and splash some water against the back of the boat.

 

[loadnet]

Re: Running engine without stern drive attached?

I would think that would make one heck of a water wash down system, thus I'd do like Wacky Charlie said...<br /><br />Put a shut off valve on the hose coming in from the outdrive and out the other side of the valve I'd put a nice little wash down hose and garden hose nozel, for when the fishies leak blood all over the floor next to the beer spills.

 

[johnkc]

Re: Running engine without stern drive attached?

the water pump impeller does need to be in working condition ,pumping water thru the upper drive to keep the upper cool.{sorry bondo} the reason that a bravo can go thru hull pickup is that the lower gearset actually acts as a oil pump and circulates the gear lube thru the drive.an alpha doesn't get the oil pump effect from the gear set .yes it is ok to run engine as long as you have water supplied to engine.but don't let full garden hose pressure build up when engine is off it may blow the sea water pump hsg.