Evinrude 4HP Lower Unit

[Xcusme]

I'm redoing the lower unit in this 'Rude 4hp,4636M,56008 . I have to replace the entire water pump housing, impeller etc, so I got the kit. I'm doing the gear case while I'm at it. <br /><br />Some rube had this apart and improperly installed the impeller and didn't fully engage the impeller pin. I suspect he ran it dry, the water pump housing melted!<br /><br />I have both the 76' OMC service manual and the parts list. Both of the lower unit seals, upper (under water pump) and lower (prop shaft ) are the same part 300599.<br /><br />I have 2 questions. First, I can't tell from the drawing which is up or down on the upper seal. Does the spring side of the seal go towards the gears or towards the water pump? . Since the seal I. D. is tapered, I'd guess the spring should go towards the gear housing so that the drive shaft won't snag on the lip upon re-assembly . Correct me if I'm wrong. The upper seal had the spring installed up when I took it apart and it didn't look right to me.<br /><br />Secondly, about the water pump assembly. The service manual shows what appears to be a nylon washer goes in the water pump cavity first, then a spacer with 2 bottom side projections, then the impeller housing cup.<br /><br />The parts manual does NOT show the nylon spacer, just the spacer with the bottom side projections and the impeller housing cup above that. The water pump kit I got didn't have this nylon washer either. Did Evinrude make a design change somewhere?? <br /><br />When I disassembled this puppy, the nylon washer was there but NO spacer with bottom side projections! That's probably why the impeller drive didn't engage the impeller. <br /><br />Should I re-use the old nylon washer or leave it out ( it's in good shape)<br /><br />Sorry for the long winded post, but I want to get this right. I just hate it when folks don't do the job right, leaving problems for the next guy.<br /><br />Thanks in advance for any words of wisdom and advise.

 

[ob]

Re: Evinrude 4HP Lower Unit

Xcusme,The spacer definately needs to be positioned under the impeller cup as it is what positions the height of the cup and impeller in relation to the driveshaft.As far as the nylon washer is concerned, I'm guessing that it was used as an oil deflector under the lip seal.Whether you replace it along with the spacer when reassembling will depend upon whether there is enough room for it (no interference)The primary function of the lip seal under the impeller cup is to seal water from entering the lower unit.For this reason it is necessary to position the seal so that the tapered side(spring side) of the lip faces toward the impeller (up).Hope this helps.

 

[Xcusme]

Re: Evinrude 4HP Lower Unit

That does make sense...Thanks for the info. I did use the existing nylon washer and it didn't raise the water pump housing too high, about a 1/10 of an inch was spec. and that's what I ended up with.<br />Pump works just fine.<br /><br />Thanks again.

 

[rikraknroll]

Re: Evinrude 4HP Lower Unit

I don't know if the 4 HP Evinrude mentioned here is the same as the one I have (I've got a Yachtwin 4 Evinrude, don't know the year) but I need to get the waterpump/impeller kit also. Any suggestions where to go/should I just go to the local marina and order the kit? This engine runs great but isn't pumping any water and the housing is completely frozen (won't budge after removing the two bolts/pouring boiling water on it: salt buildup). Any info would help.

 

[Xcusme]

Re: Evinrude 4HP Lower Unit

Rikraknroll,<br />Post the model number of your motor. Parts are readily available at your local dealer or on the web. It would be a good idea to fully disassemble the water pump to see what needs replacing. The least you'll need is the impeller and wear plate, the most you'll need is the entire pump. Either way, the parts are cheap. While you have the lower unit off, use a garden hose to force water up the water tube and flush the power head looking for good water flow. You could remove the head, inspect the cylinder walls and clean the water passages while you had it open. Remove the side exhaust cover plate and manually clean the exhaust port passages. Both the head and exhaust gaskets are cheap.