1986 43MY - Lost forward and reverse when docking

[Messi]

671s, allisons trans


Was running subject boat for a sea trial today. She ran great...until docking. Spinning round in the fairway, i lost forward and reverse. Linkage is fine. Fluid level seems Ok, with engine idling.

I would have figured if it was internal, I would have lost either forward or reverse...not both.

Where would you look next? Could the shift selector valve cause this?


Thanks!

 

[SEVEN]

Hopefully the prop didn’t spin off.

 

[rwaldrop13]

I had a similar experience with Pau Hana with the port engine. The diagnosis based on the conversations with my fellow old Coastie engineers that worked on the Detroits was an internal leak from the transmission into the engine oil thru the intercooler. They said the remedy was to drain oil and antifreeze, pull the intercooler and have a machine shop pressure test it and close off any leaking capillary tubes. I never got to test that theory but I did have low transmission oil (it happened while docking) in that engine, and it was full when I checked it the day before but was low when I reached the marina.

 

[Boatsb]

What about the pump? Is it making pressure? And what about the hours on the transmission? Ge5 an oil sample and pull the pump.

But remember she's not yours to troubleshoot and never think its worth enough discount to make it your problem.

We just replaced a twin disk for a customer. 5075sc with all the fixings (damper and cooler) was over $16k plus labor.

 

[Captain Ralph]

Seal blown on the selector valve.
Seal blown on oil pump.
Lost prop? Possible. Was the shaft turning?

These are all guesses.

A proper tech will help.

 

[Messi]

Seal blown on the selector valve.
Seal blown on oil pump.
Lost prop? Possible. Was the shaft turning?

These are all guesses.

A proper tech will help.

Full back story....I moved the boat in sepetember, about 20 miles, to try and sell for the owner who is not local. She shifted perfectly.

Started and shifted afew times for some lookers. Once is got cold, say nights below 45, the startboard trans would try and pull the dock away in neutral. Block heater reduced this, and a brief warm up, and it was gone. I had seen this on a number of boats in the past when cold, though not pulling this strongly. THEN one day instead of forward, it was pulling very softly in reverse. Ran it for survey haul, and sea trial. Spinning her around in the marina, I lost foward and reverse.

I was focused on getting her in the slip...the wind was blowing. I had a very green buyer, and a surveyor who 'wont help with docking'

It honestly feels like i lost a prop. I'm going to check pressures, and shaft rotation. I know twin discs, and velvet drives well....not allisons.


Thanks

 

[madhatter1]

Like everything else on a boat the tranny pump will work until it doesn't. Hauled for work last year for about 6 weeks. Splashed and no tranny pressure on STB. Mechanic forced the prime and got it home. Next day tried and no pressure. Got lucky, Dave had given me a spare with the boat.

 

[Messi]

So update......

Went to the boat this am to see is shaft was spinning. Have forward and reverse pretty much as normal. Fluid on that side is darker that other trans. Slightly low. 2/3s between Safe and full (while running in neutral) Will change fluid and try to run her again. I'm still wondering of selector valve is wonky. What invoved in rebuilding?

 

[neildeb2]

Any update on this?