I need some info on the cooling circuit, 1960 40hp Evinrude

[Grandpa Mike]

My son and I are resurrecting and oldie and I have some concerns about the engine cooling. I was browsing the forum and came upon reply from HighTrim re: another cooling system issue about water output.

He suggested to the OP that his motor may have blown an impeller and blowing out the cooling circuit would be a good idea. Sounds like good advice to me but I have a few questions.

In my other threads and postings, I've explained how my son and I are going through this engine thoroughly. More or less, new everything. Complete ignition system, carb overhaul, lower unit and w/pump housing & impeller. We're coming to the home stretch now and nearly ready to reassemble and fire it up. (it ran in the first place, badly...but it ran).

I could really use a diagram or detailed description of the cooling system circuit. When we first started it before the overhaul, we got fairly good output from the w/pump but the choke would not unload and the engine got too hot IMO. Water would sizzle on the head and was really too hot to hold my hand in the stream.

Yesterday when I removed and disassembled the carburetor, I noticed that the water jacket on the choke was bone dry on the inside and there was no water, or trace, present in any of the engine water water hoses.

Yeah, more than likely there are either chunks of an old impeller, barnacles, chicken bones or some other lake debris clogging a water passage somewhere. We also included a new thermostat in the rebuild goodie box. Marine engines are not my forte and I could really use some info on the routing of the cooling circuit.

Thanks everyone.
Mike.

 

[HighTrim]

Re: I need some info on the cooling circuit, 1960 40hp Evinrude

I have a good diagram somewhere, let me look through my pics on my computer, they are not all that organized.

Whenever I drop a gearcase, I always at least hit the water line with compressed air to ensure that cooling circuit is clear. Only takes a second, and saves you from dropping the gearcase twice. On your motor, remove the t stat and flush/backflush from the suspended water line and ensure it exits the t stat housing, then from the t stat housing back down to the water line.

This is also the time to inspect the water intake area and ensure it is free from debris. The rubber grommets on either end of the water line also play an important part in water flow. If they are swollen, or if the water line is jammed into them, water flow will be restricted.

Always run that motor with the t stat installed, and I like to put sealer beneath the impeller plate to ensure a good seal. That pump works better with no air introduced. Ensure the vent hole on top of the impeller housing is not plugged. Also, ensure the motor is submerged deep enough into the water. The pump is not self priming, and needs to be submerged.

Hope this helps.

 

[Grandpa Mike]

Re: I need some info on the cooling circuit, 1960 40hp Evinrude

Thanks a bunch. Any info you could find would be really helpful. I'm a whiz at auto but Marine's are new to me. Water heated chokes are not. We're getting a pretty good discharge volume. (all I have to compare it to though are online video's usually YouTube). BTW, we did start it initially submerged in a drum of water, plenty deep enough. We had already done the lower drive unit and water pump housing & impeller. My thought's were that since we have it apart, and a couple hundred dollars into it, it would be nonsense not to do anything else it may need. The flywheel, carb and a lot of other hardware is off the engine at the moment. I'd like to be able to follow the cooling circuit from inlet, though the engine & stat and to the discharge. My son has an air-compressor and blow gun and though we intend to replace all the hoses, water and fuel, any internal passages ought to be attended to now that it's accessible.

Again thanks!!
Mike

 

[Willyclay]

Re: I need some info on the cooling circuit, 1960 40hp Evinrude

My thought's were that since we have it apart, and a couple hundred dollars into it, it would be nonsense not to do anything else it may need.

You are getting great advice from one of the forum's experts so my input is based solely on limited experience with an RDSL-21 which is almost identical to your motor. First, you probably will not be able to reliably use the hot-water choke. Most people manually choke them to start and then override (OFF position) the choke after the motor warms up. Also, if you do not already have the cylinder head off and the cylinder head cover (water jacket to us old guys) removed, I suggest you do so. There is a chance of corrosion accumulating in the water passages and restricting the flow. Finally, you should test the T-stat to verify proper operation. Good luck with that great old motor!

 

[Grandpa Mike]

Re: I need some info on the cooling circuit, 1960 40hp Evinrude

You are getting great advice from one of the forum's experts

Oh yeah, I don't doubt that at all. On a ford trucks forum I'm sort of a "go-to-guy" here, I don't know squat. I've already gotten a ton of great advice that without...I'd just be taking shots in the dark. When it comes to marine engines, I'm gonna assume I know nothing. (and in truth, not much)

We do have a t/stat and I really didn't want to pull the head off unless it was warranted. It has good and even compression. If that is what is necessary to ensure a good volume of water and proper cooling, I'll do it. For all I know the thermostat is jammed or a water passage is full of debris. I just thought that with an air-compressor and garden hose, I could flush things but good. I just don't know where to connect to, and from what direction since I have no idea of what the cooling circuit of a marine engine looks like.

Oh and Willy...love the signature...as a fellow old geezer, there's a lot to be said about that!

Cheers
Mike

 

[F_R]

Re: I need some info on the cooling circuit, 1960 40hp Evinrude

You indicated you are getting good water discharge, but head is sizzleing hot. That doesn't sound just right, but I'll take your word for it. Here is how the system works:

The water pump sends water up to and through the powerhead. Then the water is presented to the thermostat for inspection. If the 'stat says it is less than its opening temperature, the water is sent back to the pump for recirculation. Then it is sent back for another trip through the cooling system. Once the thermostat is satisfied that it is warm enough, it opens and the water is discharged and replaced with fresh cool water from the lake and the whole process starts all over again.

However, the above explanation is over simplified. Even while in the recirculation mode, some water bypasses the thermostat and is discharged and replaced with cool lake water. That is necessary in order to keep the exhaust housing cool. Also, it provides you with that visual spray so you can see that it is working.

So, the thermostat is constantly sampling the water temperature and opening and closing as necessary to maintain proper operating temperature. It is not a matter of taking x number of minutes to open, and then stay open. At idle speed it may never open, especially in cold lake water, because enough cold water is being added to the mix to replace that which was discharged through the bypass.

Summing up, there should ALWAYS be SOME water being discharged. The AMOUNT of discharge spray constantly varies according to whether the thermostat is open or closed at the moment.

If you think about it, this is exactly how all cars work. The thermostat is constantly sampling the temperature and either sending the water to the lake (radiator) or recirculating it back through the engine till it is warm enough. The only difference is cars don't have to discharge some to cool the exhaust. And you sure as hang don't want to touch the exhaust pipes either.

 

[HighTrim]

Re: I need some info on the cooling circuit, 1960 40hp Evinrude

Very kind but even a blind squirrel will find a nut now and then right??

Sometimes we get lucky, and when we make a mistake we have Mr Frank Robb to set us straight.

Frank do you have a water flow diagram? I believe you have posted it before, I cannot seem to locate it.

Not much to it though Mike as F-R explained. Just flush/backflush from the copper water line and the t stat housing. If you get flow in both directions, you should be ok.

I agree with WIlly on the choke as well, do it manually.

 

[Willyclay]

Re: I need some info on the cooling circuit, 1960 40hp Evinrude

Oh and Willy...love the signature...as a fellow old geezer, there's a lot to be said about that!

I just could not resist posting in a thread started by a Grandpa. With F_R posting also, you are in the best of hands and I am out of here!

 

[Grandpa Mike]

Re: I need some info on the cooling circuit, 1960 40hp Evinrude

Outstanding fella's. I do believe I'll take it from here. With this kind of info and advice...if I can't handle it, then I'll need to weld the cover shut on my top-box and submit my man-card for review.

Thanks for all the help.
Mike.

**I know this is boating forum, all things marine but I actually am a US Marine. I just noticed I made Seaman Apprentice. I couldn't just be a PFC, Lance Corporal or something?

 

[TregoMark]

Re: I need some info on the cooling circuit, 1960 40hp Evinrude

I'd like to stress one thing regarding the water discharge. As mentioned above the discharge will vary. It will not be a solid stream at first or at idle. It will look more like a spit and spatter. When the engine is at operating temp (t stat open) and throttled up, the discharge stream will be strong.

Good luck and test the compression before anything else.