Author Topic: Velvet Drive C71 overheating  (Read 105 times)


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Velvet Drive C71 overheating
« on: July 14, 2021, 06:00:55 PM »
My C71 is overheating and apparently causing ATF loss at front seal. What is normal operating temp range. Manual indicates 190⁰ F max., 140⁰ to check ATF level. I use a 4108 double oil cooler for engine and transmission oil on the coolant circuit. Engine temp 165⁰ to 170⁰. Tranny exceeded 200⁰ on the case. 183⁰ internal measured with an infra red temp gun down the fill port. Engine running at 1700 rpm in forward gear while tied to dock.
David E. Nelson

Dale Tanski

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Re: Velvet Drive C71 overheating
« Reply #1 on: July 27, 2021, 09:35:41 AM »

Let me ask some questions...
1) How is it the transmission case temperature is hotter than the internal temperature? If that was the case the housing is adding temp to the internals and transmission oil.
2) On the 4108 double cooler, each of the oil sections is separate for each other.  So, the acceptable engine temp is only an indication that the cooling water flow is sufficient.  Is the cooling water side of the tranny oil cooler plugged or restricted? Could be an object blocking the intake of the water side of the tranny cooler.
3) When is the last time the tranny oil was changed? Oil that has lost its lubrication properties (age, abuse) will run hotter. Could be that simple.
4) I believe that Velvet Drive, on that 71C, indicates the normal operating temp is between 140F to 190F.  Due to the weird temp readings at the transmission, what is the oil temp on the way to the heat exchanger?  On the way back?

Pearson 365 Cutter Ketch
1976 Hull #40
Buffalo, N.Y.