It is running 100 degrees hotter than the other two. I will change the filter next and if that does not do it try acid washing the cooler.

we just had a triple 525 fountain in the shop w/ the same problem,found the problem in the oil t-stat housing

This is also on a triple 47 Fountain.(center motor) So the t-stat housing fixed the problem. Thanks for the info, I figured someone else has had this problem and could point me in the right direction. Thanks MIke

we found the oil t-stat piston binding in the housing,not allowing the oil t-stat to open all the way

I'd go with dollerparts, I don't think scale would cause 100 degree differences. Thermostat is a good bet at that temp (no oil flow through cooler at all).

Thanks Art. We just changed it out and put in new oil and filter and the problem is fixed. I noticed that the new one has a extra washer in there that will keep the hole open about a 1/4 of an inch. The one that came off the motor did not have this washer. I am assuming this is so if the piston gets stuck it will still let some oil go to the cooler. Also the mercury filter I got is white? But this is the correct part number according to the local dealer. Does the black one only come on the motor from the factory or do you sell black mercury racing filters? Thanks Mike

mike,they come in both colors 16595q is white and 16595t1 for black same $ for either art

So was it the thermostat or the oil filter?

Those center engines on triples from the discussions I have seen here are always finiky with water feeding, prop wash and so forth. Check the pick up and try to sdjust that if your not feeding from the drive.

Combo of both. Before the middle engine was pinning the 340 temp gauge. Changed the t-stat and ran it. It went to 260 and the PSI was down 20 from the other two motors. So we figured the oil must have boiled and separated. Changed the oil and filter and they all now run around 220 degrees and the same PSI at all rpms.