Temperature range for a Velvet Drive

[dennisspain]

This is my first post, please bear with me as I describe my concern. I have a 1986 36' DC that was stored by the PO for 5+ years. One of my first tasks was to replace the engine heat exchanger and the oil and transmission coolers. The boat has a single FL 120 and a VD with a reduction gear. On an extended sea trial the first season,, the VD overheated (300+) and died before I discovered the situation. It may have failed due to the long period of disuse and associated internal seal failure.
Pulled and rebuilt the tranny, balanced the shaft and prop and replaced the cutless bearing (whew). I also replaced the cooling hoses with 3/8" ones and plumbed the ATF to flow against the water flow thru the heat exchanger.
Needless to say, I'm hyper sensitive about that rebuilt VD and heat. I've searched the Internet and the manual, but I can't seem to find information other than that the ATF should not exceed 180 degrees.
Now at 1100 RPMs after 4 hours, using my infrared pyrometer; the transmission is pushing 200, the reduction end 170, the line from the tranny to the H E is 157 and the return is 94. I am concerned that if I press towards 1500 RPMs or God forbid WOT that the transmission is going to continue to heat up.
So finally I get to my question! What is the consensus as to the high temp limit of a VD? Does the temp of the housing even matter? Or is the temp of the ATF (<180) a sufficient metric? If you consider this to be overheating, what else should I check?
Thanks in advance for your thoughts. I'll try to not be so long winded next time.

[jleonard]

I have an old Velvet Drive manual and it says 190 F as a max.
I will be happy to send you that manual, it has a temperature trouble shooting section.
Send me an e mail and I'll reply with the manual.

jleonard@globalsteering.com

jleonard at globalsteering dot com

By the way you can also use regular engine oil in that tranny as long as the rpm is kept under 2600 which is easy if you have a Ford Lehman at 2500 rpm max. Engine oil can take a little higher temp and lubricates much better than ATF.
As an FYI, I use synthetic 5-30 in mine. When I shoot the temp at the inlet and return of the cooler I get in the 100 to 110 range at around 1700 rpm with sea water temps in the mid 60s. I never took a temp reading on the housing anywhere.
IF you rotate the cooler so that the oil inlets are at the TOP (you may have to add some plumbing to do this) you will be able to add additional fluid (about 1/2 qt) to your tranny. This will help keep temps cooler. An old timer who worked on BW trannys for 40 years told me told me this when I went to him to ask for tips about rebuilding mine.
Hope all this helps
Jay

[marinegears]

I see that this is an older post so you may have figured this all out by now. 190 deg F is the max you want a Velvet Drive or any transmission using ATF as its fluid to hit. Above that temperature the fluid starts to break down and does not lubricate properly. Velvet Drive sells a simple high temperature alarm switch, part number 1000-140-004 that can be added to you transmissions test port. Add this switch to an alarm or buzzer and you will have high temp warning system. You should be able to get one at Harbor Marine in Everett, WA. You seem to have a good temperature reduction across the cooler so it sounds like its doing its job. Can the boat reach WOT if needed? This is a good test to make sure you have the right prop, right transmission reduction and a good running engine. If you can not reach WOT you may be overloading the engine and transmission which would cause the gear to overheat at higher RPM's.

[dennisspain]

Update...
After consultation with Mike at Habor Marine (who had rebuilt the transmission), I went through all the possible causes for over heating:
1. Plumbing, the flow of transmission fluid had to be against the flow of the water through the cooler. Check
2. Linkage, the shift lever needed to fully engage the the transmission . Check
3. Correct prop, at wot achieve hull speed or slightly above, Check
Finally Mike tells me to switch to engine oil (thank you Jay) and the problem was solved! It seems that although the transmission was recently expertly rebuilt at HM, the wear on the shafts and other parts still allowed the ATF to slowly heat and allow the plates to slip adding to the temp. The engine oil has more viscosity and maintains sufficient pressure to hold the plates in place. Problem solved.
I added a temp gauge and now run happily at 140 indefinitely.
Thanks for o all the responses and assistance at HM and the replies here.

[WillieC]

This is why I love AOG and its membership. What a gift you all have provided. Problem. Questions. Here's what I have done. Here's an outdated manual. Oh, btw, here's what I learned. Put it all together, problem solved. Priceless. And some measure of peace of mind, til the next problem arises.
Way to go, members.