new thunderbolt 900 owner question

[win231]

Hi

I have a question about the normal cooling operation. I have a Mercury thunder bolt 900 think 1978 it is a 6 cyl. At idle no pee stream if you increase the speed it seems to pee strong. Looked at manual it shows a thermostat will open at a certain temp. Does that mean no pee until the thermostat opens our should you see water peeing all the time. I may order a water pump rebuild kit to be safe. Any other ideas would be welcome or other issues I should be on the lookout for with this motor. All other outboards I have owned no pee replace impeller.
thanks win231

 

[redfury]

Re: new thunderbolt 900 owner question

waterpump is probably getting weak. The thermostat will open and you will see water sputter out of the back of the motor. The tell tale is there to let you know that you are actually pumping water. Considering the cost of an impeller, it's cheap insurance that the boat won't overheat due to a weak pump.

 

[Chris1956]

Re: new thunderbolt 900 owner question

Win231, Merc inline six motors do not have thermostats. They relay on the increase/decrease of the pumping volume of the waterpump at different RPMs to provide the correct amount of cooling. They also run dead cold at idle.

It is wise to change the impeller, wear plate and gaskets, prior to use, since you do not know when it was done last. Also, change them every couple of years after that, to keep the water pump efficient.
Make sure the carbs are clean and inspect the idle pickup and max timing for adherence to spec.