Evinrude v4 overheating

[linmag]

Hi all,

First I could mention that I'm new at this forum, which I found when searching solutions for my overheating problem. Great site!

My problem is that when I run my 1988 Evinrude 90hp VRO at low or medium rpm's everything is fine, but when I go WOT the overheating alarm goes off.

So I searched the site and found three possible causes: 1) bad water pump, 2) malfunctioning thermostats, and 3) swollen/misplaced water deflectors.

I have checked the water pump and it is fine. This weekend I'm planning to check the thermostats, and if that does not help, I'll go for the water deflectors. Good plan?

But my question really ends up at the third statement, regarding the water deflectors. From what I understand the deflectors are rubber hoses of outer dimension 3/8".
My question is: Are the hoses connected to cranccase and the heads? Are there water passing in the hoses?
Or is it only a "thing" inside the water channels in the cylinders to prevent the water to pass in between the cylinders? Would any other "thing" with the same outer dimensions do the same trick? Perhaps a material that do not get swollen with age or when overheated?

Thanks in advance
/ Magnus from Sweden

 

[freddyray21]

Re: Evinrude v4 overheating

what do you mean by water pump is okay. Hard to tell just looking at one. The impellers on those change from low to high speed. At high speed they are very touchy on air leaks. If the water pump housing is worn enough or the gasket is leaking at high speed they will suck air and not water.

 

[emdsapmgr]

Re: Evinrude v4 overheating

That engine has two thermostats, each controls one half of the block. It would be interesting to know if the whole engine is overheating, or just one side of the block. Check this with a laser heat gun to know for sure. When at planing speeds, there are a pair of pressure valves in the thermostat housing that open to provide the block with additional cooling water (esp. at high speed). If these are deformed or plugged with debris, they may not be opening as designed. I'd have a look inside the thermostat housing before checking on the water diverters in the block.

 

[cdoliver]

Re: Evinrude v4 overheating

does the alarm go off when you back down on the throttle? or stay on for a while? If it goes off immediately it's a fuel restriction alarm not overheat.

 

[ezeke]

Re: Evinrude v4 overheating

That motor does not have a vacuum switch for a fuel restriction alarm, so if you have a constant alarm you are looking in the right places (for overheating).

As others have indicated, if the overheat is only one side, it's the thermostat or the water deflectors.

You can rebuild the whole thermostat system with Sierra kit # 18-3673: http://www.iboats.com/mall/partfind...gd_poid=111072&gd_row=34&**********=646655378

 

[linmag]

Re: Evinrude v4 overheating

Thanks for good insights, I'll check if only one of the cylinder banks is overheating or both next time I put the boat in the water.

But today I removed the thermostats and found a lot of "stuff" in there. I cleaned up everything. But I'll need to order new thermostats since the old ones were not operating at all. They were however stuck in open position, so perhaps I need to go for the water deflectors after all.
The pressure valves seem OK despite of all the "stuff" in there.

But before that I'll install new thermostats and go for a test run.

I hope htis will solve the problem!

/ Magnus in Sweden

 

[Dhadley]

Re: Evinrude v4 overheating

If you don't have a water pressure gauge it's kinda hard to "check" a water pump. When in doubt, change it out. The complete kit, not just the impeller. Again, if you have doubts about the deflectors, change them. Period. They should be changed every year, they need to be changed every 2 years.

 

[linmag]

Re: Evinrude v4 overheating

Okay... now I'm puzzled.

I have installed a new thermostat kit and went for a test run yesterday.

I put the bout inte the water, warmed up the engine and then opened up about 1/2 throttle. Everything works fine, so after a while I go WOT. I run it in WOT and no alarm. I feel good!

Then I back off to about 2/3 of throttle for a while and then finally I go for idle but with gear in. And what happends - the alarm goes off!

I turn the engine off and measure the temperature between the cylinder banks with my finger (not the most exact, I know, but thats what I had at hand). They feel as if they have the same temperature. And I could keep the finger at the engine about a couple of seconds.

After I let the engine cool down I tried to reproduce the settings to get the alarm to go off again (ot learn more about the problem). I run it for quite some time in different throttle setting, from idle to WOT, but the alarm did not go off again.

So it seems that I get the overheating alarm sporadically, and in different throttle settings (idle this time and WOT bofore the thermostat change).

Does anyone have a good idea what could be my problem?
I guess that since the cylinder banks had approx. the same temperature the problem could be the water pump. Anything else?

And as some have indicated to me earlier in this thread, that it is not possible to view the state of the water pump - I guess that will be my next step.
But is there anything else I could do?

Thanks,
/ Magnus in Sweden

 

[emdsapmgr]

Re: Evinrude v4 overheating

If you found a lot of "stuff" in the thermostat housing, you may also have that same "stuff" in the head cooling passages-as the debris would have had to come through the heads to lodge in the thermostat housing. I'd consider pulling one of the two head covers (not the heads themselves) and see if it has any debris in it. This is not a bad job and cheap-you only need to replace the cylinder head cover gasket. If it had debris, you can clean it out and then do the other head cover. If you do find debris in the heads, also may want to consider pulling the heads and checking the water passages around each cylinder.

 

[ezeke]

Re: Evinrude v4 overheating

If the water deflectors are in good shape and in place, I would consider starting with the intake screens on the gearcase; if they are not whole, the system will not function properly and particles large enough to block the thermostat passages will continue to accumulate.

Then backflush the cooling system after you recheck the waterpump and before reinstalling.

Recheck the fuel system completely for any leaks, remembering that if gas can get out, air can get in and run the engine lean; that will overheat the pistons and destroy the engine.

 

[linmag]

Re: Evinrude v4 overheating

Hi everyone, and thanks for your help.

Yesterday I changed the water pump and put the boat into the water,and I got no more alarms. Today I went for a longer run and still no alarms so I am quite confident that the problem is solved.

Thansk you all!

/ Magnus in Sweden

 

[kenmyfam]

Re: Evinrude v4 overheating

Glad all is apparently well.