lower unit not pushing enough water?

my boat was overheating so i bypassed the lower unit, put a hose into the t stat housing and the boat ran cool.
i replaced the lowerunit impellar. the impellar wasnt in bad shape but the lower housing that the impellar sits in looked liek it was leaking and the copper tube was all dented up.

after replacing the impellar housings and tubei got everything bakc together and ran the boat on ear muffs and its overheating again? Can i run the boat on ear muffs? it ran for 2 or 3 mins then the temp. climbed up to 220. i bypassed the lowerunit again and the engine ran cool. i dont wnat to put the boat in the water again and have it over heat.

i took the hose off the transome where the water comes into the boat and im getting water but its sputtering out not a solid stream from the lower unit?

any ideas? maybe water pump on engine no good? it is brand new. i just installed a jasper remanufactured engine in the boat.

its a 1982 searay sundancer mercruser 260 pre alpha out drive.

 

It's likely the drive impeller, but you should have it looked at by someone a little more familiar with these types of systems.

 

Hi tony45,

The fact that the tube from the water pump was dented up is rather suspicious. There shouldn't be any loose parts in there that could damage it, and any mechanic worth his wrenches knows better than to bang up parts like that. Damage to the water lines will definitely restrict the flow somewhat. It's also possible that something is partly blocking the passages- perhaps a small chunk of broken impeller vane.

The raw-water hose coming from the drive into the boat should definitely be pumping a solid, steady stream of water. Any sputtering is definitely a sign of either blocked water tubes in the drive, or a busted lower unit water pump.

Running an outdrive on earmuffs should work just as well as running it in the water. However- if you run it on shore with a garden hose straight into the motor, you still need the earmuffs on! Running the rubber impeller dry will tear it to shreds in a matter of minutes.

 

27 years is a long time in which a lot has happened. There are tell-tale signs that maintenance wasn't always done by the right people. The dented tube is the result of someone putting the drive together without properly aligning the tube with the rubber grommet on the pump. When that happens, the tube exerts more force on the top of the pump housing than is can handle. It may have cracked but is certainly warped.

Replace the pump housing and the gasket under it with the proper type. Mercruiser changed the design several times: they used plastic and stainless steel housings and combinations of these.

Also check the short hose between the upper housing and the gimbal assy. Where it makes the 180 degrees turn it may show cracks.

 

i took everything apart again. the ose from the inside of boat to outside the transome is clear. I blew out the inside of the outdirve, everything is clear. i replaced the copper tube. I put white lithium grease on the impellar is that ok?

im gonna try my buddy outdrive today to see if his works.

 

The impeller is a consumable piece, just like an air filter. It's intended to be replaced every year. That particular impeller is about 10 bucks, replace it and it would also be good advise to R&R the whole pump assembly, as has been suggested. You can Mickey Mouse with this thing all day, making guess after guess, or bite the bullet and take it to someone who is familiar with these things.

 

i changed the outdrive and now its running cool, so its deff. something with the water pump. i have a friend gonna look at it, but i changed the impellar every year, what could have gone different this time.