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Radiator up high or below under motor?


Active member
Im doing a few upgrades.

The radiator is one of them. Right now I have the radiator up high above the motor. No cooling issues but since Im replacing to a new aluminum radiator I might consider puting the new one under the the motor attached to the engine stand while Im at it.

Is worth it. Is is better? Ive seen both on all types of boats.

I have a 12x8 3/4 deck aluminum boat with a 500DD. Its hunting boat. I ride in tall grass a lot. My opinion is its still better to leave up high?...

Thanks in advance!


Well-known member
I can tell you this, don't let words such as "HEAVY DUTY" or "RACING" guide your purchase for the replacement aluminum radiator. Focus on the size, number of rows and tube diameter. If you relocate it or refabricate keep this in mind. Moving the radiator 4 inches further away from the prop created a 10 to 15 degree temperature increase to a boat we built with a very large and efficient Griffin radiator. The Cadillac does not like to be hot so heed that advice.

Recently I have seen a boat with a radiator marketed as "heavy duty" and it is a rock solid radiator. One problem is the tubes are so thick they don't shed the heat so well. As such I would suggest you really shop the specifictions and keep the radiator close to the props airflow.

pontoon outlaw

Well-known member
I got mine under the motor, close to the prop, plenty of airflow for the Cad 507 and yes Swamp is spot on with the core of the radiator mine is a 4 core, cools very nice runs 160 to 180 during the Heat of the day even in tight Trails or mowing down the Grass along the Tree line :thumbleft:

happy harold

Well-known member
the transfer of weight will be a big help in handling. be sure to add a GOOD expansion tank. you will be glad you made the switch when you look over your shoulder.

Olf Art

Silent Prop
R. I. P.
Here's something to consider. Because airboats are a 'pusher prop' setup it's real important to protect air in-flow to the prop. Riggin, seats, radiators, oil coolers .... all of that stuff tends to mask off the available air to the prop, and that means less push. I'd personally want my radiator down under the engine, with only an expansion tank above it. JMO