Transmission Running Hot

[daviddodd]

I need a little assistance from the mechanic guys out there. 1999 Carver 350 Mariner. Port side transmission is running hot. The v-drive is cool. Engine is cool. Changed the trans fluid and motor oil last week on both 350 hp vortex engines. Also cleaned all water filters to assure no issues with water flow to the cooler. Typical service each year so included changing the impellers and checked the water flow at the lines. I have not checked fluid flow at the cooler which is Saturdays job. Any advance would be appreciated.

David

[tomschauer]

No specific answer but ….
Usually the raw water goes to the engine, then vdrive, then tranny. If you are low on water flow the vdrive or tranny will suffer first as the water is hotter when it gets to them. Is your impeller good? Then, is your trans heat exchanger fouled, then, not sure of your tranny, but is there a fluid filter and did you change that?

[mjk1040]

Short of pulling the tranny heat exchanger, you may want to try a descaling of the fresh water cooling system. Mix up a 5-6 gallon RydLyme mixture and let it set in the system for 6>12 hours or so. If you have any exhaust steam, descale them engines.

[daviddodd]

Tom, I puller the impeller to check for broken pieces that have come off and causing obstructions but the impeller was intact. Went ahead and installed new since I had it out. The fouled heat exchanger is interesting. We are checking water flow in the out flow side by pulling the water line. Removing and installing a new one is no big deal. Easy to get too.

Mike. I did notice exhaust steam from the engine. Can you provide steps for descaling? Our lake is closed so it appears I will have time to do alot of maintenance work.

So my task appears to be 1. Check outflow of water at exchanger, 2. descale, 3. and then of all fails replace exchanger.
Please let me know if you other ideas.
Thanks
David

[bud37]

You can back flush the lines to check for bits....look inside the heat exchanger for plastic and look thru the water tubes in the exchanger to check for corrosion and build up.

You can back flush your thru hull raw water intake....maybe some plastic or growth in there.

Question....you changed the trans fluid, what color was the old fluid...nice pink like fresh trans fluid or shades darker ?

[Viper]

All the above suggestions are valid ones. It would be good to know the make and model of the transmission we're talking about here. Does your application have the separate Walter V-Dives? What leads you to believe the transmission is overheating, do you have a gauge indicating such, or are you taking an external comparison to the other transmission?

Finding an intact impeller in the pump doesn't eliminate the possibility of impeller pieces in the cooler from a previous impeller failure, though that isn't applicable to some cooler designs. It would also help to know the make and model of engines you have as not all coolers are built the same, and looking through a particular design doesn't tell you anything. Are these engines fresh water or raw water cooled?

If the transmission is indeed overheating and is not due to restricted raw water flow/volume, there may be a transmission issue and the condition of the fluid is important to note as mentioned. When does it overheat, and how long does it take? Does it overheat in neutral if you run her at 1500-2K rpm (no higher), or only in gear, and at what rpm do you need to achieve for that to happen?

A few other checks:
- Check to ensure that when you shift into gear, the lever on the transmission is fully engaged and can't travel any further.
- Check to see if there is any shaft creep (spinning in neutral).
- If the model has an oil filter, change or clean it depending on type.
- Is the fluid at the correct level and how are you checking it?
- Are you using the recommended fluid type?
- After a run, and while removing the dipstick, do you hear a release of air pressure?

Mike, I think you mean descaling the raw water circuit, not the "fresh water cooling system"

[daviddodd]

Guys. Thanks for the advice. We will start working on the boat this week and I will report back a we complete each task you listed.