1971 Lightwin overheating issue?

Hello,
This is my first post so i am a little long winded. Sorry.
I just got my hands on a 1971 Lightwin. The motor is in good shape but i know nothing about it's history. I need a little help in figuring out if i have a heat issue or not. First i ran the motor in my test tank. I shut the motor down after about 3 minutes. i touched the power head and felt it was hot. it was not hot enough you would have got burned. This is a noticeable difference in comparison between my lightwin and a 1954 evinrude 15hp I have that is cold to the touch. When running i did notice that water was spitting out of the 8 little ports. For some reason i thought there should be more and not knowing the history of the motor i checked the water pump condition. I peeked into the housing and everything seemed good.

Today i took it out on the lake. Same thing. The motor seems a little hot in comparison to my other. I ran it this way for a while stopping from time to time to check the motor. If you flicked water at the head you could get it to sizzle (a little) if you hit directly on the head. You could get nothing on the sides of the motor. Water did spit out of the ports. Nothing was blocking the intake. No loss or change in performance. No issue stopping and the restarting. There is no previous signs of heat. ie:discolored paint on the head.

Re: 1971 Lightwin overheating issue?

You could possibly have a little bit of corrosion build up in the water passages to constrict the water flow. I have a 1970 model here and I didn't see a thermostat on it, so that wouldn't be the case. So, I would take a check through all the passages and see if it has any corrosion build up. I have picked up motors in the past that have been through salt water and not flushed out properly. Unfortunately, the water passages were completely closed off and had to be scraped out completely.

Re: 1971 Lightwin overheating issue?

You don't mention the last impeller change. If you don't know when it was done, change it. You should be able to hold your hand on the top of the head for a three count. It sounds to me like it is O.K. but if you have any doubt, change the impeller. Your 15 should be running a lot hotter than it is so don't use it's temperature to compare. Best of luck, Rick.

Re: 1971 Lightwin overheating issue?

Update:
I pulled the head and removed the exhaust cover. I noticed the inside had a brown clay like mush on the walls of the water jacket. Not completely blocked but like a coat of paint. Poking around one of the holes by the exhaust cover that is 1/8 inch had been half closed. I sprayed some CLR in the water jacket and blew some chunks out. I plan on doing some more cleaning and then call it quits and put it back together for a test in the tank. The inside of the water jacket was wet when i opened it which shows me it was cooling a little. I am hopping there is no damage. I would not think there would be and on the other side it most likely had been run that way before.
Thanks for all the help