Thermostat bad or weak stator fouling plugs?

[V153]

Re: Thermostat bad or weak stator fouling plugs?

Not tryin to be an ahole, but what exactly did your mechanic rebuild? 100 psi in one hole, 120 in another. Thermostat/overcooling problem, etc. Don't think I'd wait 15 months to get worried?

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

He had to re-sleeve one cylinder and re-honed the other three. The re-hone only roughens up the surface. It doesn't re-bore and square off any really small iregularities. He told me that it's too soon to check the compression because the rings haven't settled in yet. He also told me that the ring gaps were all right at .015. I have a 3" bore so .015 ring gap is what I needed.

As for the cooling issue, we think we have eliminated that as the cause. I haven't checked the temps yet. I have to get a laser temp gauge first and then take it out on the water to get a real world reading.

Weather is going to be rough tomorrow. Looks like I'll have to wait till next weekend to get the temp readings.

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

I will say this about my mechanic........he's a good guy. He told me that he wants to get to the bottom of the cold start issue as much as I do and to not worry. If I blow up the motor, he'll fix it or rebuild it free of charge whether it's 15 months or 15 years. He wants to stand behind his work and he knows he has a new lifetime customer. He's a great guy and a good friend.

We'll get it figured out and I'll report the issue here to follow-up.

 

[trendsetter240]

Re: Thermostat bad or weak stator fouling plugs?

The mechanic is correct it is too early to get accurate compression readings. However, 100psi is very low for new rings. It should be closer to 120psi now then rise to 130+ after the rings are set. Take the motor out and run it hard to set the rings.

 

[trendsetter240]

Re: Thermostat bad or weak stator fouling plugs?

Did he put new rings in all cylinders? Your compression numbers kind of lead one to believe he only replaced the one piston and rings that show 120psi.

 

[emdsapmgr]

Re: Thermostat bad or weak stator fouling plugs?

Due to the way the crossflow blocks were machined at the factory, it is considered normal to have compression variances between heads. Does not always happen, but you could see a variance of between 5 to maybe 8 lbs between heads. This really does not explain the wide compression variance between the heads on your engine. Any chance you are running non-matching heads? If a ring ever let go and damaged an original head, a prior owner could have mixed heads on the block. 324528/529 are the head part numbers that should be cast onto original heads for a 79 85 hp. Those heads were standard on the 85/100 and 115 that year. 125 lbs compression is a good number after the rings seat on a fresh rebuild.

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

Update.

Motor is running about 115 degrees on all 4 cylinders. Definately not 140 per spec.


Initial start was fine (like always). After running on hose, 115. Took the boat to the lake and 30mins after initial start, doesn't want to run. Acts as if its starving for fuel or not running right air to fuel ratio. Bulb is a bit soft when truing to start so I pump bulb while its running rough. Motor dies after 10-15 seconds.

Trim motor down and pump bulb motor dies. No pump bulb, motor starts and runs rough due to fouled plug. Change plugs, motor starts.

Plugs are fouling due to motor running cold. Once motor is running, plug unfouls and I'm off and running great. No problems.
Sounds like a Carb issue to me. Mechanic swears Carb was good at rebuild bit never got a chance to test drive. I think it may need a different needle or float adjustment. That would fix the temp issue I think. Right?

Also, original heads on motor. Has never been cracked open until now. I'll wait to see what the compression is.

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

I should add that the water temp was 47 degrees which will affect the motor temp.

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

Any further thought on this?

 

[trendsetter240]

Re: Thermostat bad or weak stator fouling plugs?

Any further thought on this?

It's clear the motor is not running right. You have a 15 month warranty, bring the motor back to the mechanic and get it fixed. Your compression results are poor, your engine is running too cool, etc.

Your mechanic may be a good friend but this is not what you expect from a properly rebuilt engine.

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

So what causes a motor to run cool?

Also, does 47degree not lower the engine temp? Granted it shouldn't make a 25 degree difference.

I want to say its bad plugs but once the motor is warm and running, it runs fine and will restart really fast. So that tells me its something else.

 

[trendsetter240]

Re: Thermostat bad or weak stator fouling plugs?

So what causes a motor to run cool?

Thermostats stuck open.

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

Oh yeah. We talked about that already.

So the temp drops even cooler when I'm on plane and nit idling. I let it idle for 10-15mins and got 115 from the laser temp gauge. My gauge on the console went from cold to below cold as if it were not working when the boat was on plane.

Thermos are a real pain to get too and would need to remove the powerhead to get to them to test them.

Might explain why it acts so cold after it has sat for a while. Fast idle is non-existent when its cold. It has to run for a min before it will fast idle.

Guess I will be taking it back. He did have a good point. Its a rare circumstance that both thermos would be stuck open at the same time.

 

[trendsetter240]

Re: Thermostat bad or weak stator fouling plugs?

Oh yeah. We talked about that already.

So the temp drops even cooler when I'm on plane and nit idling. I let it idle for 10-15mins and got 115 from the laser temp gauge. My gauge on the console went from cold to below cold as if it were not working when the boat was on plane.

Thermos are a real pain to get too and would need to remove the powerhead to get to them to test them.

Might explain why it acts so cold after it has sat for a while. Fast idle is non-existent when its cold. It has to run for a min before it will fast idle.

Guess I will be taking it back. He did have a good point. Its a rare circumstance that both thermos would be stuck open at the same time.

Yeah, the thermostats should've been replaced during the rebuild as a matter of course. It's unfortunate but you shouldn't be having all these problems after paying someone to rebuild the motor for you. Hope it all works out. Would like to hear what the mechanic has to say about all your troubles.

Cheers

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

A few more questions to ease my mind...

- What are the chances of both thermostats failing or staying open at the same time? Is it due to scaling or 30yrs of muddy water usage? (because this boat has had 30yrs of dirty water run through it due to lake it was on)

- Also, there is no way to get to the thermos on this model without pulling the powerhead is there?

- If the thermos are stuck in the open position, water should come out of the exhaust overflow ports below the cowling when the motor is still cold correct? I should be able to start my motor on the hose cold and see water come out of the exhaust ports pretty quickly after starting (I'm predicting this will happen)


And finally, is it normal for the motor to "shimmy" while idling? I don't recall the motor doing this before. It's not bad, just barely noticable. While on plane, the motor is moving quite a bit more and I don't recall the motor moving at all before. It's almost as if the mount had slack in it.

Here is a video showing the motor at idle with the shimmy. I don't think you can see the motor shaking while on plane.

1979 Evinrude V4 85hp - Motor Break in Trials - YouTube

 

[trendsetter240]

Re: Thermostat bad or weak stator fouling plugs?

The thermostats probably failed over time, not necessarily both at the same time. They should be replaced every few seasons or anytime you have an over / under cooling issue.

I'm not sure where they are located on that motor; I would think they would be in the cylinder heads. Can you post some pics of the motor from the back side?

I watched your video, the engine sounds fine to me actually. A little rough at idle but that's probably just a very minor carb adjustment that is needed.

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

The thermostats are located below the exhaust plate. Due to the design of the cowling, it's next to impossible to get to the exhaust ports were the thermostats are located. You have to remove the power head from the motor so you can remove the lower shroud to access the thermostats. I was hoping someone knew of a shortcut for this particular model.

The motor sounds terrific when it's running. I think the cold motor is causing the fouled plugs and that is contributing to the hard start issue after the motor has run for a while because the motor cools down rapidly and has fouled plugs. I really think I'm getting to the cause of the issue. Due to the warranty, I'm not pulling the powerhead. My mechanic can do that.

 

[trendsetter240]

Re: Thermostat bad or weak stator fouling plugs?

That sucks about the location of the thermostats. I guess they hadn't quite got it all figured out by 1979.

 

[seahorse5]

Re: Thermostat bad or weak stator fouling plugs?

the V4 thermostats were always on the adapter plate like that in various configurations since 1958.

It if it not a saltwater engine, they are fairly easy to replace using a flex 1/4" drive socket - 7/16" hex

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

the V4 thermostats were always on the adapter plate like that in various configurations since 1958.

It if it not a saltwater engine, they are fairly easy to replace using a flex 1/4" drive socket - 7/16" hex

Thanks. I wondered if I could use a flex drive. I bet its a pain to get the bolts started when reinstalling.

Can I remove the lower cowl? I think you have to remove the powerhead to remove the lower cowl right?