Allison Gearbox repair

After my last deep sea fishing trip, I lost thrust to the port side fwd engine. Reverse was still good.
After checking various causes, including re-building the Hydreco oil pressure pump, my mechanic said it was most likely the seals in the gearbox and the flywheel assembly.
So, yesterday we started the work in getting the gearbox off the motor and getting access to the flywheel at the rear of the motor. Lucky we have good access thanks to a well re-designed engine room. Thanks Merritts!

Unfortunately, it has turned into a lot more work than expected (doesn’t it ALWAYS!)

When we pulled the flywheel off, the clutch plate was almost worn back to bare metal and clutch material was all over the area. No wonder I found so little clutch material in the screen/filter in the early diagnosis time, there was not much left!
Also, the worn clutch plate meant metal to metal wear onto the piston, which is so badly gouged that we will have to get a replacement. Hopefully I can find one locally.
Looking for a cause we think we found it. The seals have a metal backing (brass?), and parts of this was all over the area. Explains why there was no oil pressure.
What amazes and even angers me, is that the previous owner had both engines replaced with fully overhauled 12V71n’s.
BUT left the original gearboxes. The starboard seems good. The oil stays fresh, while the port went black almost immediately.
Lesson learnt for next time: check that the gearbox was rebuilt when the engine was.
I will post more as we progress.

Gearbox Repair

Preparing the gearbox for removal from the engine. Then removing the Flywheel.

Thanks, I noe have the web site noted. I will email them early next week if we have no success finding parts locally. Considering how many Detroits and Allisons are in Australia, I am told we may find the right parts in good time. But there are a lot of calls to be made.
Cheers.

Yeah, thanks James. Hoping to get it done without too many surprises.
Learning as I go and have a good mechanic.
Have a good weekend.
George

I wouldn't want it more tight! One of the reasons I settled on this 53, in spite of the lack of "toys" was the engine room. Hate the idea of poking around an old ER not knowing what has been done by various owners over the years.
Good luck RT46

More images will be posted as I progress, it won't be a clean ER for a while.
We have had to order a new piston from the US. I was hoping to get one here, even a second hand one that had been reconditioned, but no luck. Hope to get it via FedEx shortly.

Gearbox Repair

Next stage of repairing the port gearbox, an Allison, finally is complete.

With the help of a very knowledgeable Detroit mechanic, I have learnt a lot about my engines and the gearbox.
We needed a new piston as the old one was so badly scoured due to the failed clutch.
I could not get one in Australia and ordered one from Dieselpro.com in the U.S. Within 6 days it arrived in Brisbane, Australia. Great service.

Next we removed the old rear main engine seal, then re assembled the flywheel, piston etc. and replaced the gearbox.

I had the sea trial yesterday and all seems good. Although the first 5 minutes were heart stopping when I found there was little thrust from the engine and the revs were going way past the normal W.O.T.
After going back to idle speed for a few minutes, then going to full throttle again and the prop now had “bite” and was running normal.
I think it was due to the Hydreco pump needing to prime itself.

Image 1: Flywheel.
image 2 and 3: New Piston.

Attached Images:
New Clutch.
Rear Main Engine Seal.
Removing the old engine seal.

Removing the rear main engine seal was a bit of work. First we tried with a screwdriver, but finally had to drill the outer metal part of the seal to break it and then pull it out.

Finally re-installing the gearbox

Not sure on that one, I wil ask the question!