'89 mercruiser 3.7l impeller direction

knehdn

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Motor began overheating. Checked for water from exhaust - none. Dropped bottom end to access impeller. Old impeller
completely void of fins. Got a new kit, so a couple of questions.
Do I need to use any kind of gasket glue on the new gaskets?
And when looking down into the impeller housing, which way should the fins point? Clockwise? Counter clockwise?
Please and thank you.
 

stonyloam

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OK the impeller turns clockwise, so the tips of the fins would point counterclockwise. Turn the shaft clockwise when you install the impeller and you will be OK. In any case once installed the fins should orient themselves correctly when you start the engine. You waited WAY too long to change the impeller, for a 470 the impeller should be changed every other year, 3 years max. Now you need to find the fin pieces. Remove the front end cover from the exchanger, any large pieces should have been trapped by the front starboard set of tubes, but it would not hurt to remove the rear cover just to make sure.
 

Bt Doctur

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To be clear, if your looking DOWN at the water pump housing the direction is clockwise per stony.
 

Bondo

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And when looking down into the impeller housing, which way should the fins point? Clockwise? Counter clockwise?
To be clear, if your looking DOWN at the water pump housing the direction is clockwise per stony.

Ayuh,.... 'n because the shaft turns clockwise, the tips of the impeller point counter clockwise,....

Now you need to find the fin pieces.

A very important point,....
Also back-flush the hose from the H/E, back to the raw water pump, before ya put the lower unit back on,....
 

savetexomabeaches

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Waterpump will correct itself no matter which direction you put it on, but the main thing is finding the fins from the old one. Check exhaust bellows, check hose before ps/oil cooler, back-flush, back-flush, back-flush. === As for a sealer, I wipe just a tiny tiny tiny tiny bit of Perfect Seal on the housing. And I do mean tiny tiny bit.
 

stonyloam

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Yeah Bondo is correct, take the forward hose off the exchanger, put in a garden hose and backflush. Pieces may have gotten caught where the hose fits on the tubes of the water cooled voltage regulator.
 

Bt Doctur

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there are no cooling tubes, its just a section of hollow pipe. the broken pieces are likely lodged in the HX tubes
 

stonyloam

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there are no cooling tubes, its just a section of hollow pipe. the broken pieces are likely lodged in the HX tubes

Yes it is just a copper pipe but It does does reduce the diameter at that point, and there is a chance a large piece could get caught there. Like you say any other large pieces are likely in the forward part of the exchanger.
 

Watermann

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Put the gaskets on dry, no need for any goop. Don't over tighten the water pump housing bolts. How does the wear plate and cup look, if grooved up they should be replaced as well.
 

knehdn

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I haven't any overheating problems till I started the winterizing process. The old impeller was a pain to get off. Brass bushing took some working to get it loose enough to remove. I'll take the covers off the heat exchanger and remove the fresh water hoses and flush them out. I'll let you know what I find tomorrow.
 

knehdn

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Well, I removed the fresh water hoses and started flushing. Found many pieces of the old impeller at in-feed of the heat exchanger once I removed the forward cover. I flushed the in-feed hose from the outdrive to the voltage regulator and heat exchanger. That section of hoses was free of debris. Then reverse flushed the tube from the outdrive towards the outdrive. Some debris did become dislodged. Wonder if I need to remove the exhaust elbow assembly with all the hose clamps? I can't see much getting caught up in there.
 

stonyloam

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Nope, anything that got through the exchanger tubes will be pretty small and will have been flushed through the tube into the exhaust and are long gone. If you take the aft-most (raw water) hose off of the exchanger and stick a hose in it, water should flow freely out of the outdrive.
 

knehdn

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Thanks Terry. I'll be doing that today, considering it'll be 20 with a humidex of 26. Go figure for the 1st. of November.
 
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