1971 50hp Evinrude - Overheating Saga

[71erude]

I have done the following things to this engine:

- Waterpump Kit
- Carb Rebuild
- Lower Unit Change
- Remove water jacket cover, clean passages
- Remove cylinder head, clean passages
- Remove exhaust cover (inner and outer), clean passages
- Replaced Thermostat
- Added Tell Tale (as per forum retrofit instructions)

Verified water at following locations:

- Pee hole (strong flow)
- Thermostat
- Exhaust cover water flow entry

Initially the boat would overheat just at idle. Now will idle all day (seems to get slightly hotter than should) I can touch cylinder head for 2 count.

Did a water test today. Overheated after two minutes at 3/4 throttle.

I've scoured other forum posts, but I'm just not sure what I should do now. Are there any other passages I could be missing, anything i'm not considering?

These forums are great. I'm learning so much, i'm just stuck for now.

 

[EN2]

Re: 1971 50hp Evinrude - Overheating Saga

Is there a large rubber grommet on top of the w/p housing? [around drive shaft]

 

[71erude]

Re: 1971 50hp Evinrude - Overheating Saga

Yes, that grommet is in place, as well as the one connecting the water tube to the top of the water pump assembly.

I should also note that i've done a compression test andd have roughly 150psi on both cylinders.

 

[71erude]

Re: 1971 50hp Evinrude - Overheating Saga

Okay -- I have some more information, hopefully helpful.

I pulled the lower unit again. I connected a garden hose with a hose clamp to the bottom of the water tube going up to the power head. When I turn on the water the only place that water comes out is the pee hole. None through the exhaust. This shouldn't happen, right? So a passage must be blocked. I don't fully understand the water path through the engine and I don't have a diagram. Does anyone have information for this motor.

Should my next step be to remove the powerhead? I honestly don't know exactly how to do that and the manual I have doesn't explain it in any detail. How many bolts, where are they?

-Chris

 

[71erude]

Re: 1971 50hp Evinrude - Overheating Saga

Here is looking up into the leg. When I hook a garden hose to the water tube water only comes out the pee hole. Shouldn't it be coming out of A and B in the photo?

 

[tashasdaddy]

Re: 1971 50hp Evinrude - Overheating Saga

hate to say it but pull the water jacket, and see if it is getting there. and tstat. the tstat has to open to get water out the exhaust.

 

[71erude]

Re: 1971 50hp Evinrude - Overheating Saga

gotcha, i'll try that tonight. thanks.

 

[bigpoppakdog]

Re: 1971 50hp Evinrude - Overheating Saga

I would bet you don't have those two sleeves in place. When I changed my impellor last year, those were the most frustrating part of the whole process. You have to be patient and work them into place...kinda hard considering you are holding the lower unit with one hand and trying to keep those in place with the other hand.

 

[71erude]

Re: 1971 50hp Evinrude - Overheating - Update!

Re: 1971 50hp Evinrude - Overheating - Update!

Okay, so I removed the water cover and pulled the thermostat and poppit. 4 Replaced the cover (14 dang bolts) Sure enough water flows through the engine fine. Up the water tube and out the exhaust. So that's a relief.

But the thermostat was brand new and opens in a pot of water on the stove. Is it possible it's defective?

Also ... I noticed that about 1/2 way up the water tube (i shined a flashlight up there) there is a hole in the side of the water tube, shooting an approx. 1/8" stream of water. I'm assuming this is not by design, right? Could that leak be causing the WOT overheating?

 

[mattblack]

Re: 1971 50hp Evinrude - Overheating Saga

i am having the exact same problem i changed the impeller and thermostat but it is still overheating. i will look at my boat tomorrow to see if mine shoots out water 1/2 way up the water tube. also do you know the best way to flush out the system?

 

[a70eliminator]

Re: 1971 50hp Evinrude - Overheating Saga

How are you guys determining an actual overheating condition? The only thing you can acurately measure by laying your hand on the head is your theashold for pain. The watertube in my evenrude also has 2 tiny holes about 6" up the tube, i though they were air bleeds but someone else says they squirt onto the exhaust housing to cool it, but there is a wall of water inside there anyhow.

 

[mattblack]

Re: 1971 50hp Evinrude - Overheating Saga

the hot horn going off is how i am determining the overheating.

 

[71erude]

Re: 1971 50hp Evinrude - Overheating Saga

When mine overheats water will boil on the head.

 

[UZLMIAMI]

Re: 1971 50hp Evinrude - Overheating Saga

Dont know if you still have the problem but here you go anyway. Hope this helps.


<a href="http://s17.photobucket.com/albums/b93/Uzl/?action=view&current=water_passage.jpg" target="_blank"><img src="http://i17.photobucket.com/albums/b93/Uzl/water_passage.jpg" border="0" alt="Photobucket"></a>

 

[pmpiper]

Re: 1971 50hp Evinrude - Overheating Saga

This diagram is for a 9.9 to a 15 HP, the problem is with a 40HP
Phil