1973 Evinrude 115: Overheated today, what next?

[fatboyntn]

I knew I should have replaced the impeller before taking her out this morning, but I did it anyway. Bad mistake. So she overheated about 1000 ft after leaving the no-wake zone. (30 seconds or so) I immediately shut the motor off, removed the cowling and inspected the motor. It was making a sizzling sound. Flicked drops of water on both power heads and they were both above the boiling point of water. After rowing back to the doc (and boy was that fun), 45 minutes later, the horn would still sound when the ignition was placed in the "run" position. After bringing it home and allowing it to cool, I verified that it had not seized. I could still crank and briefly allowed the motor to start. The paint on the power heads is now discolored and has "peeled" from some of the head bolts. Not a good sign.

Here is my plan.

* Do a compression check.

* Remove the heads and inspect the pistons, cylinder walls, water jackets and water restrictiors.

* If no damage is found, replaced the head gaskets and install the heads.

* Perform another compression check.

* Replace the waterpump, impeller and housing.

* Inspect and rebuild the thermostat.

Does anyone have any other advice to offer? This is the first time the motor has ever over heated. I inherited the motor from my late father. As far as I can recall, the horn has never sounded in the controlbox.

Thanks in advance,
Terry

 

[tashasdaddy]

Re: 1973 Evinrude 115: Overheated today, what next?

if compression check is good, just do the impeller and tstat. then try it.

 

[fatboyntn]

Re: 1973 Evinrude 115: Overheated today, what next?

Well I replaced the impeller last week. It was completely destroyed. The housing looked good, so I just replaced the impeller and gaskets. After getting the motor back together, I put it on the muffs and fired it up. Uh oh. I should have checked the compression. It started and ran just fine, but there was water leaking around both heads after it warmed up. Once I noticed this I shut the motor off. I suspect at the very least, it has warped heads and blown head gaskets.

I plan on purchasing new heads and head gaskets. When I remove the heads I will examine the cylinders and pistons for any damage.

Any more advice would be appreciated. I promise to follow it next time

Thanks!
--Terry

 

[tashasdaddy]

Re: 1973 Evinrude 115: Overheated today, what next?

heads can be dressed, no need for new ones unless cracked.

 

[ezeke]

Re: 1973 Evinrude 115: Overheated today, what next?

Water has surely gotten in to the cylinders, so keep them heavily lubricated until you have the heads back in place with new gaskets. Rotate the flywheel clockwise to distribute the oil.

 

[kenmyfam]

Re: 1973 Evinrude 115: Overheated today, what next?

Great advice above. Heads can be re-surfaced and dressed if slightly warped. Only issue is taking too much off to get a good surface again depending on how bad they are.

 

[fatboyntn]

Re: 1973 Evinrude 115: Overheated today, what next?

Thanks for all the advice guys! Where should I take the heads to have them resurfaced and dressed? A local machine shop?

Also I have removed the heads and have found some small remnants of the impeller in the water passages. Any advice on removing these? Compressed air maybe?

The pistons and cylinder walls appear to be in OK shape. Anything special I should be looking for?


Thanks!
--Terry

 

[tx1961whaler]

Re: 1973 Evinrude 115: Overheated today, what next?

You can dress the heads yourself with a piece of glass and a sheet of sandpaper. Put the glass on a very flat table, tape the sandpaper face up, put the head face down and sand it in a figure 8 to even it out.

 

[fatboyntn]

Re: 1973 Evinrude 115: Overheated today, what next?

I took the heads to a local machine shop that specialize in small motors. They were cleaned and milled. They look great. I am expecting my gasket set to be here soon.

I am thinking of either doing the telltale modification to this motor or installing a water PSI gauge in the dash. Do you guys have any opinions about which I should do?

I don't want to have to go through this again and I think the gauge would get more attention than the telltale once out on the lake.

Thanks!
Terry

 

[F_R]

Re: 1973 Evinrude 115: Overheated today, what next?

Sounds like your impeller disintegrated. In many cases, they came unglued from the rubber. You wouldn't believe how many of those I've seen do that. Either way, when it happens, it is so quick that chances of you looking at a guage or tell tale at the moment are slim to none. In fact in most cases it is so quick that the horn doesn't even have a chance to go off. You got lucky.

Did it melt the sender unit for the horn? Usually does, and that needs to be replaced as well.

In most cases, the pistons are damaged. To check them, remove the exhasut cover plate from between the cylinders. You need to do that anyway to replace the gaskets which are most surely cooked and leaking from the heat. They are the hottest part of the engine, hotter than the heads. Even if they are not leaking to the outside, they may be leaking to the inside, which is even worse. Internal leaks risk squirting water into the cylinders through the exhaust ports. When that happens, it is all over for sure.

 

[fatboyntn]

Re: 1973 Evinrude 115: Overheated today, what next?

The overtemp sending unit appears to be in excellent shape. It seats firmly between the head cover and the head. The little rubber stopper does not appear to be deformed and the spring is still good and stiff.

I don't quite understand your last paragraph. I thought the reed valves would close on the intake stoke. I don't see how water could make its way into the cylinder unless there was a reed failure.

Also, I was not aware there is a waterjacket under the exhaust cover. Learn something new everyday!

Thanks!
--Terry

 

[fatboyntn]

Re: 1973 Evinrude 115: Overheated today, what next?

I got the heads on last night. Ran a compression check this afternoon. Looks good to me. #1-110 #3-110 #2-105 #4-110 psi

I also drilled and tapped the block for a water pressure sensor.

Maybe tomorrow I will start it up!

 

[kenmyfam]

Re: 1973 Evinrude 115: Overheated today, what next?

So far so good then.
Please keep us all posted.

 

[fatboyntn]

Re: 1973 Evinrude 115: Overheated today, what next?

I started it up this afternoon after installing the pressure and temp gauge. I had a couple of small issues.

I had water leaks where the hoses connect to the heads. I suspect that the original claps may have lost some of their ability to clamp after I removed them. I placed some gasket sealer around the connection point on the heads and used an aftermarket hose clamp. Problem solved.

I also had a small water leak around where I drilled and tapped the block. I wrapped the sender's threads with Teflon tape and reinstalled it. That problem was solved.

The last problem was a small drip of water under the port head. I suspected that I didn't get it tight enough. I was not able to get the torque wrench in that area and properly tighten the fastener when I installed the heads. I tightened it by guess after the engine cooled. The drip stopped the next time I started the motor. So I think that issue is solved.

The water pressure gauge takes a couple of seconds to start indicating pressure. It shows about 5 PSI at idle.

The temp gauge never got much over 100 degrees Fahrenheit after several minutes of running.

There are literally a couple of drops of water that seep out from around the center fasteners of the exhaust cover housing as the motor warms up. Is this something to be concerned about? should I replace that gasket too? I know it was mentioned earlier.

Thanks for everyone's help!

--Terry

 

[ezeke]

Re: 1973 Evinrude 115: Overheated today, what next?

The thermostat (vernatherm) on your motor opens and closes at +/- 105? F. so 100? is good to go.

The leak in the exhaust cover ought to be repaired with two new gaskets and sealer. Is your exhaust cover a bubbleback or flat?

This is what F_R was referring to earlier. The surface water is not the problem, but if the water leaks behind into the exhaust manifold, the water can flow back into the engine through the exhaust ports and do significant damage.

 

[fatboyntn]

Re: 1973 Evinrude 115: Overheated today, what next?

Hey Ezeke,
Thanks for the reply! I have ordered OEM#317914 gaskets. I am not sure if it is a bubble back or not. The outer exhaust cover does have a "hump" in the bottom right corner. I don't know if it is a "bubbleback" or "flat" cover.

Anything special I should know about removing the outer and inner cover?

Does the water flow between these covers?

Thanks guys!

--Terry

 

[fatboyntn]

Re: 1973 Evinrude 115: Overheated today, what next?

Hey guys,
Good news! I replaced the gaskets on the inner and outer covers. It is no longer dripping water when it warms up. I also found a couple of large chunks of the impeller in between the covers, so it is a good thing this was checked.

The bad news is that I found fuel spraying out of the back of my fuel pump. I opened it up there was a small tear in the bladder allowing fuel to get to the back side of it. I have ordered an OMC P/N 438559 to replace it with. I understand that to be a direct replacement for an OMC P/N 385784.

Hopefully I will be out on the water later this week!

THANKS GUYS!

--Terry

 

[kenmyfam]

Re: 1973 Evinrude 115: Overheated today, what next?

Keep us posted and good luck.

 

[fatboyntn]

Re: 1973 Evinrude 115: Overheated today, what next?

Well I took her out after installing the fuel pump this afternoon. Fired right up and idled great. Had a small issue @ WOT on my first pass. It would kinda lunge at 3/4 throttle with no increase in power @ WOT. I stopped and noticed an oil slick around the stern of the boat. I removed the cowling and found fuel was leaking around the fuel pump's output terminal. I took a pair of pliers and moved the factory hose clamp to create a more snug fitting. Took er for a 2nd run. MUCH better. 42MPH (gps speed) @ 5100 RPM WOT. Felt strong and responsive! Time to replace those old hoses and awful factory hose clamps.

Thank you guys for all the advice and help! I have said it before, and I want to say it again. This is one of the finest bulletin boards on the Internet!

Regards,
Terry