omc stern drive raw water pump

[danthern]

I have a 1977 23 ft. cruiser with an OMC 235 hp 351W I/O, was a gift from my father in law. The block was cracked, replaced it. One and only time I put it in the water it ran extremely hot. (I had been running it in the yard on the hose). Had water in the oil afterward. I took loose the raw water supply hose from the outdrive. With the drive submersed in a horse trough, no water was being pumped up.Bad impeller, right? Figured I had blown a head gasket or worse, so I tore it down to the head (didn't see a blown gasket), carefully inspected the block, had the heads magnafluxed. Got new gaskets for the heads, exhaust and intake, put it back together and it runs like a charm. Tore the outdrive down to replace the impeller, and it's brand new looking, definitley not my pumping problem. What else can it be? Bad seal, etc? Any input is greatly appreciated.

 

[Bhamil]

Re: omc stern drive raw water pump

Sounds like you've had a time of it! The only way for water to get into the crankcase is to get there past the rings; even a blown head gasket won't allow water into the crankcase. So, I believe you still have a problem, even if it appears to run good. I would do a compression test and check each cylinders PSI against one another to verify good compression, then if you do find a problem, you can eliminate that. The water pump can cavitate and not pump water. So, a good pump can have a bad seal and no water will pass to the engine, at least not enough to cool a V8. A stuck thermostat will cause it to overheat, too, so I would replace that out of hand. It's fairly easy to get to and inexpensive.

 

[danthern]

Re: omc stern drive raw water pump

Thanks for the advice Ben. I did replace the thermostat, a compression check is next on my list. I'll keep you posted.<br />Thanks

 

[rodbolt]

Re: omc stern drive raw water pump

hello<br /> if some one put the hinge caps on and put the port side on the stbd and the stbd on the port it blocks the water passages and the seawater pump will not supply water to the engine. usually happens when someone has the drive off, the caps will physically fit both ways but only work one way. have you tested the manifolds and elbows? if the block froze and cracked its possible the manifolds and elbows and intake manifold cracked as well.<br />good luck and keep posting

 

[danthern]

Re: omc stern drive raw water pump

Thanks for the tips. The exhaust manifolds, risers and elbows are all nearly new and crack free. I'm reasonably sure that the intake is o.k. I was able to get to the raw water pump without taking the stern drive out so it was not removed by me, anyway. The hinge caps that you mentioned, are they the rubber things on either side near the top of the upper unit? If so, I believe that I have had them off in the past, I think to lubricate something...??? The quest continues....keep that advice comin!!

 

[tie_one_on]

Re: omc stern drive raw water pump

Had a learning experience with type of set up myself. First thing, replace the hose from the intermediate housing to the thermostat housing with a clear piece of hose. Check the hose while the boat is running in the lake. The hose should be filled with a solid flow of water, no air bubbles. If you have air bubbles, this will cause the engine to over heat.<br />First check while idling:<br />If you have air bubbles, most likely the impellar. Since you may not know the age of the impellar that's in there, replace with new one. Get a whole water pump kit. Probably $40-$60.<br />Second check while under motion:<br />Again, the clear hose should be filled with solid flow of water. If you have bubbles in this test, possible problems:<br />Loose water pick up tube in the cavitation plate (that's what my problem was)<br />Some type of restriction caused by corrosion along the water flow route (follow your manual)<br />Good luck.<br /><br />Oh by the way, I ultimately ended up reapowing with Vovle Penta. Love the boat, just needed reliability.

 

[Boomyal]

Re: omc stern drive raw water pump

WFB, it's the caps behind the rubber pads that rodbolt is speaking of. The caps have the zerk fittings on them and are held on by the two bolts that the rubber pads hook over.

 

[danthern]

Re: omc stern drive raw water pump

Thanks for the suggestions, my puters been down and just got a new one today. Found the problem!! There is a thin metal plate between the impeller housing and the swivel housing that wasn't sealing and was not allowing the pump to work. Pumps nicely now. Gonna be in the 70s here this weekend, may give it a test run. I'll keep ya'll posted. This site is great!!