Logo
FULL SITE MENU

Evinrude 70hp Overheat Alarm

K

Klink

Regular Contributor
1990 Evinrude 70hp I am fixing for free for a friend, it is overheating, alarm goes off. Here's what happened till now in brief:

- engine ran cold, 100 degrees and would not warm up. It idled very fast. I couldn't do a link and synch because it would not warn up.
- I checked the thermostat and it was the old style and the vernatherm was stuck open. I put in the updated OEM 0434137 thermostat, 140 degrees .
- I then did the synch & link
- I put in a new water pump kit complete, aftermarket from Ebay (see picture below)

Took the boat out for a test, took it at idle speed through the no wake zone at like 1500 RPM, then took off and planed beautifully, it ran for a minute then the alarm went off. Went back home, removed the cylinder head to clean it (typical overheat cause in Florida). It was not that bad, really didn't need a cleaning that bad. Cleaned it put it back together with new head gasket, and I installed the new style one piece thermostat seat for salt water.

Tested it today. It planed fine and ran at high speed for 300 yds, turned back and ran it back at high speed, it ran fine. Tried the run a second time and the alarm went off, I slowed down to idle and the alarm turned off in 30 seconds. I checked the temperature at the top of the head where the manual says to check it and it was 148, I checked it at the bottom cylinder of the head and it was 160, which is normal for this engine (or is it?).
When I checked the temperature, the alarm had already turned off, so it could have been hotter before. ​
When it overheated there was white smoke/steam coming out of the overboard 2 exhaust holes. I idled back to the dock and came home.

I'm going to take the gearcase off and check my water pump installation, and also for possible blockage in the tubes.

Anything I should look for?

Water pump kit 70hp.jpg
 
Last edited:
It includes 2 thermostat springs and a thermostat cover, except for the big spring all those parts do not fit my 70hp. I had bought the big spring separately before. It also looks like it has two peephole hose connectors and some other parts that do not apply to my model. The only part that was missing in the kit I bought was the O-ring that goes on the end of the drive shaft, and I bought that separate.
 
Last edited:
This engine also has the cooling system bulletin upgrade from 1992(?) where they moved the pee hose outlet to on top of the engine.​
 
I have not seen water come out the two overboard exhaust relief port holes when I ran it in the tank at up to 2000 rpm in neutral. Shouldn't I see water coming out of there? I should've checked that when running in the lake at high speed, but didn't think of it as I am not familiar with this engine yet.
 
Last edited:
Klink said:
I have not seen water come out the two overboard exhaust relief port holes when I ran it in the tank at up to 2000 rpm in neutral. Shouldn't I see water coming out of there? I should've checked that when running in the lake at high speed, but didn't think of it as I am not familiar with this engine yet.
Click to expand...
When running on muffs you might not see water out the relief ports. When the engine is submerged and the thermostat opens you should see water out the ports.
 
I tested it with muffs I looked at this video and tried the same method, muffs and quick acceleration bursts, but no bursts of water came out


I tested in a tank, a big rectangular plastic bin, the water level was above the intake and below the lower exhaust relief ports, six holes on both sides and on top of the cavitation plate. No water came out the two top exhaust relief ports. I put my hand to block the 6x2 lower relief holes and it made no difference.

I'm going to see if I can find a tank that goes deeper in, but so far it does not look good.

Any observations from the pros?
 
Tested it in a deeper tank that covers well above the 6x2 holes exhaust ports (see picture), and all that comes out of the two exhaust relief ports on top is some spit at idle from the Port hole only. When I give it bursts of revs to 3000, nothing but smoke comes out, no bursts of water like in the video above. I noticed that most of the exhaust comes out on the port sides of both the top (2 holes) and bottom (6holes x2) exhaust ports. When I cover the left 6 holes it comes out the starboard 6 holes, but when I cover the top port exhaust, it does not spit it out the starboard.

Evinrude 70hp sample - Copy.jpg
 

Attachments

  • Evinrude 70hp sample - Copy.jpg
    Evinrude 70hp sample - Copy.jpg
    44.7 KB · Views: 1,333
Last edited:
Took the gearcase off, and disassembled the water pump and everything seems in order. Will take off the thermostat and cover off and flush it out from the bottom intake tube with a hose and see what happens.
 
Last edited:
I installed the ebay pump kit on May 22, 2018. I sea trialed the engine on July 2, 2018 and it overheated within one minute of running her at planing speed 4000-5000 rpm On 11-2-2018 I put the head back, with new head gasket, and a new thermostat face rubber seal on the head. I sea trialed the engine again and it overheated again, this time I was able to run about 600 yds at 4000-5000 rpms before the alarm went off. I dissembled the the water pump and found the impeller has a permanent bend to it and creases in the rubber. The impeller has had about maybe 1 hour of running time all of it but 3 minutes at idle speed. The impeller has been in the engine from May 22 till today November 6, that's 6+ months.

I've always been told to replace the impeller when it has a permanent bend. This is what the impeller looks like (Am I wrong ?):

Ebay impeller.jpg ​
 
Last edited:
Personally I'd replace that impeller... and if that's one you replaced just recently and it has that curvature... I'd suggest that you replace it with a factory one (Bombardier).

In looking at your graphic with the yellow line. It's a little hard to tell exactly where the water level would be but obviously it's above the joint line. However... you know where the water pump is and the height of it... have the water pump completely submerged less the pump will draw air.

On a flushette, the water needs to be turned on Full Blast!

On the boat, unless you're into racing heavily and know exactly what you're doing... that cavitation plate should be parallel with the bottom of the boat and approximately 1/2" - 3/4" (no further) below the bottom of the boat/keel. Yes I know that engines that are PTT equipped, that won't be a permanent setting BUT it is a rigging setup.
 
racerone said:
Impellers just like tires are all BLACK, but they are not all the same !!
Click to expand...
Agreed. 99% of the time I go with OEM parts only. I’ve always used Evinrude OEM water pump kits....the entire kit, not just the impeller....and have always had good results.
 
kevinj said:
Agreed. 99% of the time I go with OEM parts only. I’ve always used Evinrude OEM water pump kits....the entire kit, not just the impeller....and have always had good results.
Click to expand...

I learned my lesson on this one. This 70hp has had a lot of upgrades regarding the cooling system. I'm going to go back to square one and get the whole BRP OEM pump kit. All the other Johnson/Evinrude engines I've had (all from the 1990's) 6hp, (2) 25hp, 115hp, and even a Yamaha 115, all registered about 138 at the cylinder head on the surface on each cylinder, when I tested them with a flusher. This 70hp is at 168-170 on the bottom cylinder, and the cooling passages in the cylinders and head are spotless.
 
I had a similar problem on a 1983 Evinrude 70hp. Turned out the rubber exhaust gasket between the upper and lower unit was misplaced when reassembled. Exhaust pressure would displace the water in the cavity above the water pump and force exhaust gas into the water pump causing the overheat because it wasn't getting water.

Just a thought.
 
capnlazy said:
I had a similar problem on a 1983 Evinrude 70hp. Turned out the rubber exhaust gasket between the upper and lower unit was misplaced when reassembled. Exhaust pressure would displace the water in the cavity above the water pump and force exhaust gas into the water pump causing the overheat because it wasn't getting water..
Click to expand...

Good to know that gasket was so crucial. I didn't think much about that gasket, and some of them were beat up on engines I worked on. The one on this one is Ok, but changing it with the new BRP water pump kit would not hurt. Thanks.
 
Klink said:
I learned my lesson on this one. This 70hp has had a lot of upgrades regarding the cooling system. I'm going to go back to square one and get the whole BRP OEM pump kit.
Click to expand...

Two days ago I ordered the complete BRP water pump kit
432955 — WATER PUMP REPAIR KIT, (INCLUDES IMPELLER HOUSING) ​
from marinenegines, it should arrive tomorrow.
 
Last edited:
Klink said:
Tested it in a deeper tank that covers well above the 6x2 holes exhaust ports (see picture), and all that comes out of the two exhaust relief ports on top is some spit at idle from the Port hole only. When I give it bursts of revs to 3000, nothing but smoke comes out, no bursts of water like in the video above. I noticed that most of the exhaust comes out on the port sides of both the top (2 holes) and bottom (6holes x2) exhaust ports. When I cover the left 6 holes it comes out the starboard 6 holes, but when I cover the top port exhaust, it does not spit it out the starboard.
Click to expand...

OK, I removed the $34 aftermarket Ebay water pump kit (which had like 1/2 hour of running time) and installed the new BRP kit 432955. I tested it in the big tank, now when you give it burst of 3000, it shoots water out of the two exhaust relief holes just like in the video above, and the engine runs cooler. Before, at 1800-2000 rpm, the bottom cylinder was at 170F. Now it is at 148F. If you leave it at idle speed for a while , the bottom cylinder will get up to 170, but the slightest increase in RPMs, brings the temperature down to 140's. The problem was the aftermarket $34 kit.

After testing it, I installed the telltale upgrade included in the kit, removing the old restrictor at the end of the pee hose and putting in a piece that basically allows the hose to hang out through the engine cowling. The telltale outlet from the engine block had previously been upgraded to the location at the top of the engine. Although the telltale hose is 3/16" ID, the new restriction comes from the 90 degree elbow at the top of the engine to where the hose connects, the ID of the elbow barb is about .140". The original restrictor was about .100. Apparently the new pump kit puts out too much water, so they increased the restriction size to release the water pressure on the thermostat.

Will try to sea trial it in the next few days to give it the final test.


​
 
Last edited:
Sea trialed it today, ran around in it continuously for about 45 minutes at 4200-4500 rpm, and about 1 hour at 1500 rpm. It cools fine now. Everything points to the problem having been the aftermarket water pump kit. Lesson to be learned, buy only OEM pump kits.

The End
 
Back
Top