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boatn4fun

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"I have a 198 degree thermosta

"I have a 198 degree thermostat in my AQ151A and the gauge runs right on the edge of red (where the themostat opens). This dosen't seem right to me that Volvo Penta would send out new boats with the gauge running right on the edge of red. I was going through my shop manual and it shows the 198 degree thermostat for this motor but, it also reads 181 thermostat for a closed cooling system. I have a fresh water cooler and I am thinking of putting in the 181 thermostat to give me a little more time if the boat decides to overheat. What do all of you think?. Can this cause any harm?"
 
"The right thermostat for your

"The right thermostat for your engine starts opening at 180ºF and is fully open at 197ºF, so it seems that you have the right one installed. Going to a 181ºF thermostat may clear (temporarily) the symptoms but will not solve the problem.

You should check your raw water hose connector in the outdrive, they tend to corrode and then the pump sucks air instead of water and the engine overheats. This is a very common problem in Volvo AQs."
 
I have checked the complete ra

I have checked the complete raw water system from the outdrive hose connector all the way through to the end of the exhaust manifold. All hoses and ports are clear and flowing freely. When I read my manual it looked as if it had two listings for the thermostat on this motor but I wasn't sure. With my gauge always hovering so close to the red I thought that maybe I had the wrong thermostat. Is it normal for this motor to run between 185 and 200?
 
"Yes, it is normal with the 19

"Yes, it is normal with the 197ºF thermostat, which is installed for higher fuel efficiency. However, when you are running close to the higher limit, two factors to consider are the cleanliness of the hull and whether you have the right propeller installed for your boat size and weight. A fouled hull and/or a propeller with too much pitch/diameter could be overloading the engine. How many RPM does your engine achieve at WOT? It should be between 4800 and 5500."
 
You may want to try a prop wit

You may want to try a prop with 2" or 3" less pitch and see if the temperature goes down.
 
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