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4.01 Liter Over Heating

snielsen

snielsen

Well-known member
I am new to air boats and have recently acquired a small boat (make unknown) with a 4.1 liter GM V8 I am running a 68X36 Florida Air Prop. I am having a problem with over heating, It will run fine for a couple of hours then blow of water from the upper cap vent and than its down hill from there. I have replaced the radiator and the water pump. There is no thermostats in the system. The radiator is mounted low and in front of the motor stand. What do you guys think?
 
On the prop side of the engine stand? It needs to be with in a few in. of the prop. Or you may want to run a thermostat with the guts tore out of it or a morso restricter kit to slow the flow of water so you cool better. (better heat transfer)
 
How is your cooling system setup? Do you have a radiator cap at the system hi point? Do you have a radiator overflow/expansion tank on your cooling system?
 
It's a matter of trial and error, everyone here has pointed out very good things to take into consideration, I run a direct drive boat 350 chev , no thermosthat, the radiator is mounted within two inches of the prop, a radiator overflow/expansion tank is a must, I have a radiator cap up top at the fill point and also on the radiator itself.
 
I do have a radiator cap a the top, I have jury rigged a expansion tank for now out of a 1 gal. jug. I haven't run it yet with the expansion tank. I'll try moving the radiator.
 
What Cad. motor is a 4.1? What did it come out of? If You pick up on everything in this post. You will have a hard time getting it hot. Don't want you to wast a good motor over a cooling issue!
 
I agree there are a lot of knowledgeable people on this site, more so than me, don't waste a good motor over a cooling issue,
 
I had a cooling problem with my dd 350, put a 1" restrictor in and solved problem. Its just a flat piece of aluminum that has a 1" hole in it and goes where the thermostat went.
 
It was called the 4100 motor, a 250ci. all aluminum Cadillac motor. I haven't seen one of those on a boat in a long time. I remember one of those on an 11ft aluminum deckover that could be picked up by 3 people(2 in back 1 in front) that was a real good running boat and another that i saw out to my camp about 20 years ago. Both of those boats were running the speed props that were out at the time. They were short, below 60" and were designed to spin up around 4400-4500rpm. i have always wanted to do something with one of those motors, might be a good lightweight reducted motor.

Larry
 
It came out of a 83 deville or ceville. It is the aluminum block.

I'm going to try the gutted thermostat. When I check the temp drop across the radiator its only a couple of degrees.
 
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