evinrude 40hp lark 1968 water pump trouble

redsmufc · #1 February 26th, 2008, 02:43 PM

Can anyone help me? I have recently rebuilt the lower unit on a 1968 evinrude 40hp lark.

I have put it all back together and i have no water being pumped out.

I have taken it apart again to check for blockages, if the 2 tubes are located properly, and if the impellor is the correct way round. all seem ok put still not working.

I have replaced all the seals in the lower unit, the grommets and the seal on the bottom of the inlet tube. and still have no joy.

It seems to be a pick up problem.... please HELP!!!!!

redsmufc · #2 February 26th, 2008, 04:11 PM

I have just been told that it could be the inlet tube seal not seated correctly, or the impellor plate not sealed.

Could this be the answer??????

R.Johnson · #3 February 26th, 2008, 04:21 PM

If you remove the thermostat cover while running, do you have any flow at all?

redsmufc · #4 February 26th, 2008, 04:26 PM

I have check that out and there is nothing reaching that point also check tubes for blockages and they seem ok. Thanks for reply

R.Johnson · #5 February 26th, 2008, 04:37 PM

Did you put in new pump parts? Have you checked the inlet screen? On top of the pump housing there is a thick o-ring, this must be in place, is that there?

redsmufc · #6 February 26th, 2008, 04:42 PM

the inlet screen seems clear i have fitted new seals to the pump housing and new seals on the tubes, and the oring is brand new aswell..

iwombat · #7 February 26th, 2008, 04:51 PM

remove the t-stat cover and hook a hose up to the inlet tube (w/ LU off). You should get a nice unrestricted water stream when you turn the hose on.

R.Johnson · #8 February 26th, 2008, 04:52 PM

Is that an all new water pump, including the housing?

redsmufc · #9 February 26th, 2008, 04:54 PM

have done that and there is a constant flow thanks

redsmufc · #10 February 26th, 2008, 04:57 PM

hi the pump housing is not brand new although it looks fairly new. i did re seal it though.

iwombat · #11 February 26th, 2008, 04:59 PM

Well, that removes a blockage from the list.

Maybe you should describe your set-up for testing this motor. Muffs or barrel. If barrel how high is the water on the midsection?

R.Johnson · #12 February 26th, 2008, 05:04 PM

If every thing is as you discribe, I am lost as to where the problem is. As the other post ask's how are you testing?

redsmufc · #13 February 26th, 2008, 05:06 PM

i have been testing this in a barrel i filled it to about 4" above the water pump housing level..

is there anyway of testing the pump is picking up without the lu being connected to the main unit??

also should i try re sealing the impellor plate??

or is there a special way of installing the seal on the lower part of the inlet tube???

R.Johnson · #14 February 26th, 2008, 05:30 PM

Not only seal the plate down, look at the walls' of the cavity under the plate, and see if there are any cracks', or breaks'.

redsmufc · #15 February 26th, 2008, 05:41 PM

i don't think its cracked but i'll double check tomorrow to make sure. Its starting to baffle me

many thanks for your help!!!!!!

Evinrude Boater · #16 February 26th, 2008, 05:57 PM

Mine is cracked. I hope that isn't a problem for pumping water. As I understand it can allow exhaust gases into the water and heat things up.

redsmufc · #17 February 26th, 2008, 06:02 PM

im hoping its something i've done maybe not sealed properly i hope lol

Evinrude Boater · #18 February 26th, 2008, 06:04 PM

The drive shaft is 5/8" diameter so if you have a 3/4" chuck you can spin it in a barrel and see what happens.

redsmufc · #19 February 26th, 2008, 06:09 PM

many thanks ill give it a go

HighTrim · #20 February 26th, 2008, 07:00 PM

I assume you remembered the impeller key right?

R.Johnson · #21 February 26th, 2008, 07:13 PM

Evinrude Boater: There was a OMC service bulletin on this in the early years of these type engine's. The cracks' can cause the condition you discribe. Did,nt we discuss your engine in an earlier post, with some idea's on how to fix it?

K.B · #22 February 26th, 2008, 07:58 PM

Just now read the post. I have a 71 40 hp ev. that I had trouble w/a couple of yrs. ago when it was new to me. May not have a bearing on yours but sounds familiar to me. My head gasket was blown and would NOT pump water. Wrench told me to check the compression and see if the gasket was the problem and sure 'nuff. Replaced and been @ 110 on both cyls. ever since.

Just for the fun of it all, check.

K.B · #23 February 26th, 2008, 08:02 PM

Oh yeah, mine has no thermostat so I know nothing about that kind of problem. "Flathead" so to speak!

R.Johnson · #24 February 26th, 2008, 08:14 PM

K.B That certainly is not out of the question, it certainly seem's to be a puzzle.

Evinrude Boater · #25 February 26th, 2008, 10:49 PM

Quote:

Originally Posted by R.Johnson

Evinrude Boater: There was a OMC service bulletin on this in the early years of these type engine's. The cracks' can cause the condition you discribe. Did,nt we discuss your engine in an earlier post, with some idea's on how to fix it?

You're right R.Johnson, mine has a few cracks and I think I will JB Weld them.