74 40HP Norseman puking gas

[vh2q]

Sierra makes an impeller for about $30 but maybe not good quality? When I put impeller in I greased it good per the manual. Then when I was messing with carb I had it in a garbage pail can't say for sure exactly how deep but certainly covering the two flanges (it's a long shaft) and it spat out some of the grease. Water inlet is way down low with some aux holes on the side cover. Both inlets were under water. On a long shaft the pump sits between the two flanges so I believe it was submerged. But after I had the lower off for testing I put in in the garbage pail as deep as it would go without water flooding into the lower unit itself, so I could observe the pump outlet (up to the lip of the lower flange and maybe that was not enough). But by then I think it was toast anyway. For the future I will heed your advice about priming ... next time the boat will be in the water when I run it, forget garbage cans.

 

[hardwater fisherman]

If I run in a barrel I put it as deep as possible. Up past the clam shells just under the exhaust relief. Just curious to know what is the part number for that Sierra impeller? I have been looking for one but the OEM one is NLA and I have not seen a Sierra one. BRP is offering an upgraded water pump kit with a plastic housing, and stainless cup. And has an impeller with stubby vanes and appears to be thicker. It was used on commercial 40hps from 1981 until 1986. I finely have mine running well again so maybe next year I will go for the new kit.

 

[oldboat1]

When you flush with a hose as you did, you should see water coming back down and out the leg -- in quantity. I'm not aware that the '74 has a pee-hole, but pushing water up through a tell-tale would not necessarily mean it has gone through the cooling passages in the powerhead.

Here's a diagram of a '74 40hp gearcase, also showing the extension: http://www.iboats.com/Gearcase/dm/cart_id.370596591--session_id.644137645--view_id.1550132 . The plate above the propeller is the anti ventilation plate (sometimes called the cavitation plate), and the main water intake is below that on the in front of the prop. It's on the prop side of the exhaust -- with that intake screen (#15). The water pump is a few inches above the intake, and the water level has to be 5 or 6 inches above the pump -- on your longshaft, at about the top of the housing extension (#62). As you see mentioned often here, these pumps are not self-priming.

When flushing look for blockages in the screen as well.

 

[vh2q]

I checked the screen when I had it apart the first time and again after the disaster and it seems clear. Will check all that again including the passageway up into the pump housing.

Had a piece of clear fuel hose hooked up to water pipe, nice tight fit. Then hooked that to garden hose also tight. Water poured down the leg as well as came out the port on the back of the leg. There was no doubt all the water went up the water pipe. Why it appeared to come back down two different ways is a mystery to me. Maybe there is a break in the water pipe???

In the diagram, what is part 58 and 59? I don't recognize these. My water pipe comes all the way down and goes into the grommet on top of the water pump.

Sierra are good guys. They are sending me foc a new impeller and some head gaskets as well. The impeller part no. is 18-3006 impeller

 

[oldboat1]

Think that's an extension when adding a conversion kit to a short shaft motor. Factory long shafts might have come from the factory with the longer tube (guessing). Your water circulation sounds right -- some diverted out the port. Doesn't sound like there are any blockages (specialized wasps apparently -- carb only).

 

[hardwater fisherman]

That impeller 18-3006 is listed for a 1971-1973 motor. And is equal to OMC part number 378891. But the OMC part number listed for 1974-1976 is 0386165 and no Sierra part is listed for 1974-1976. I do not know what the difference is but it appears to me that that is the wrong impeller. And the reason you have water coming out in two places is most of the water goes out with exhaust just above the main water intake. And some is sprayed out through the exhaust relief ports.

 

[vh2q]

Good catch hardwater .. mine is a 73 not a 74 and I gave the sierra guys the model, serial and that's the impeller they are sending. Model 40355D. My BMW 2002 is a 74 I sometimes get confused!

 

[hardwater fisherman]

As a 1973 you have a better ignition system than if it was a 1974. And your impeller is much cheaper. They can be found for 16 dollars right here at IBOATS. I think the drive shaft for the 74-76 models is a larger diameter. And that is why the impellers are different.

 

[vh2q]

Happy to say impeller is impelling and motor is running cool. Thanks all.