53MY transmission removal question

[MikeP]

Does anyone know from previous experience if the prop shaft on a 53MY/M20/8V71TI can be disconnected/moved rearward far enough to provide sufficient clearance for the transmission to be removed from the engine without removing the rudder?

My starboard tranny has always been slow to engage forward gear during it's first use of the season - 10 second delay - but from that point on has engaged immediately even if the boat sits for a couple of weeks before operating again. However, this season it has been slow to engage , 4-5 seconds, at the day's first start, even when operating the day before. All subsequent shifts are immediate.

The fact that this characteristic has changed rather suddenly leads me to the conclusion that it's time to pull/open up the tranny and do a rebuild. I want to do this with the boat in the water since we live on the boat and have nowhere to live if the boat is pulled but that may not be possible depending on the clearance available.

 

[Pascal]

Pardon the simplistic suggestion but have you checked for an air leak near the screen? Is it possible that the issue is a seal which leaks when cold but seals properly when hot? What does the pressure gauge show before the first shift vs later

 

[saltshaker]

I'd also look for a suction leak first. I believe you can pull the gear without too much trouble. I've never done it on a 53 MY but we did it on my 46C and I know of at least two 53 owners who did theirs while in the water.

 

[MikeP]

Thanks for the suggestion! The pressure comes up immediately upon engine start whether cold or hot to around 120PSI at idle - reading via mechanical gauge in the engine room.

I talked to Acadian a few years back re the delay at first startup of season and they advised that "some of them do that." So it was never an issue to me at all since it only occurred at that first start-up of the season. But clearly, something has changed...

I checked the strainer a few years back when I was first investigating the delay/talking to Acadian and there was no leakage. If it was leaking, I would expect the pressure to be low. Both port and star tranny pressures are within spec per the Allison tranny service manual - I checked them again yesterday when cruising.

 

[dsharp]

If you can't get the shaft back far enough you can loosen the mounts and raise the back of the engine enough to go over the top of the coupling. The hull is strong enough to block the engine up at the bell housing.

 

[saltshaker]

If you can't get the shaft back far enough you can loosen the mounts and raise the back of the engine enough to go over the top of the coupling. The hull is strong enough to block the engine up at the bell housing.

You have to do this anyway as the rear engine mounts are on the gear housing.

 

[SeaEric]

Here is a photo of the prop/shaft/rudder clearance on Cinderella. As always, your clearance may vary.

 

[Glory]

I think the space issue is in the ER, between the coupling and the stuffing box. I'm going to guess there is.

JM

 

[SEVEN]

You might want to install a remote pressure gauge in the engine room to verify the PSI is correct. My gauges read 200 to 225. The remote gauge reads 145. You may find there is not enough PSI and might need to be adjusted.

 

[Cricket]

Having been through a few Allison failures on different boats I always found they were fine until they failed. This seems like more of some type of adjustment issue with the pressures, pump, selector valve, cables, etc. Have you had anyone come take a look at it that know's what they're doing? If it was me I wouldn't be rushing into exploratory surgery just yet. Btw, a few weeks ago I had Twin Disc come out for what was thought to be a leaky output seal and ended up rebuilding the gear. My initial thought was to put it on a pallet and ship to Acadian for the rebuild, I didn't and now I'm really pissed at myself.

 

[MikeP]

Thanks for the suggestions. I installed mechanical gauges in the ER many years ago so all temp/pressure readings are from those gauges. The only thing I use the helm gauges for is to observe relative changes.

I agree that the issue could be an adjustment BUT, the pressures are correct per the gauge so it's not a hydraulic pump problem (both of which I rebuilt a few years ago). IOW, there is nothing incorrect about the pressure and therefore nothing to be adjusted in that regard. I ran into an interesting comment in the service manual a few minutes ago that I'm going to check. The manual states that if water temps are low, the 40 wt oil might cause the problem and further states that in that case, warm up the engines for 20 minutes with tranny in neutral before engaging. I'm going to try that in a couple of hours when we head south to St Michaels. Of course, even if that makes a difference, the port tranny does not exhibit the same behavior so something is different between the two...

I checked the linkage and at full deflection forward, the tranny linkage is full forward as well.

 

[saltshaker]

Having been through a few Allison failures on different boats I always found they were fine until they failed. This seems like more of some type of adjustment issue with the pressures, pump, selector valve, cables, etc. Have you had anyone come take a look at it that know's what they're doing? If it was me I wouldn't be rushing into exploratory surgery just yet. Btw, a few weeks ago I had Twin Disc come out for what was thought to be a leaky output seal and ended up rebuilding the gear. My initial thought was to put on a pallet and ship to Acadian for the rebuild, I didn't and now I'm really pissed at myself.

It's been a long time since I had my Allisons but back then Acadian only worked on Allisons. Do they now do other gears?

 

[saltshaker]

Mike I had a pump that seemed to be fine with no indication of low pressure. Symptoms were the same as yours. Pump was a rebuilt unit I bought from Acadian. I called Brian and he sent me another pump. Problem solved. My mechanic and I where skeptical but it worked

 

[bobk]

Mike, When my shaft was pulled back for this purpose, it required a very good cleaning to allow it to move. A diver tried and that was a waste. Probably speaks to the quality of the diver but once cleaned properly, the shaft on the 48MY moved back plenty far.

Bobk

 

[Cricket]

Called Acadian and they gave me some rough numbers to rebuild our Twin Disc 5114a, so yes.

 

[SKYCHENEY]

I pulled the shaft back on my port engine and disconnected the trans from the engine to install clutches. It was tight, but there was enough clearance. But, I do not have OEM stuffing boxes. I have PSS Dripless. YMMV, but there should be room.

 

[rsmith]

Does anyone know from previous experience if the prop shaft on a 53MY/M20/8V71TI can be disconnected/moved rearward far enough to provide sufficient clearance for the transmission to be removed from the engine without removing the rudder?

My starboard tranny has always been slow to engage forward gear during it's first use of the season - 10 second delay - but from that point on has engaged immediately even if the boat sits for a couple of weeks before operating again. However, this season it has been slow to engage , 4-5 seconds, at the day's first start, even when operating the day before. All subsequent shifts are immediate.

The fact that this characteristic has changed rather suddenly leads me to the conclusion that it's time to pull/open up the tranny and do a rebuild. I want to do this with the boat in the water since we live on the boat and have nowhere to live if the boat is pulled but that may not be possible depending on the clearance available.

Did it change after you ran aground?

 

[MikeP]

Did it change after you ran aground?

No. there was no change re that. Only difference after running aground was the boat was faster! (might have been a tide/current/wind thing but we were going pretty much the same direction on the river and only about 20 minutes difference between previous full power run and subsequent one after doing the mud route!

Interestingly, as I said previously, yesterday morning I did the 20 minute warm-up as per the Allison service manual for low water temps/40 wt oil. Tranny shifted promptly when engaged on first start up of the day! So is THAT the actual issue? Could be, I suppose. I believe the water temps ARE lower than they have been when I have previously been here to re-comission but there is still the issue that the port tranny does not exhibit that same level of behavior.

Of course, it's possible that IF the water temp makes a difference, the internal clearance variations within each tranny makes a difference in how they react.

I checked pressure at the ER gauges again yesterday at the Allison spec RPM (1800 in forward) and the pressures are right at 130, as per the manual.

Again, the star tranny operates absolutely perfectly in all situations OTHER than the cold start/first engagement delay to forward and yesterday, after the cold start/20 minute warm up, there was no delay.

I think I will just "monitor" for now and see what happens as water temps rise.

 

[JonHupp]

My Allision M20 Horror Story...

As another Chesapeake Bay resident and new owner (9/15) of a 53MY I'll fill some of you in on my ongoing M20 problem.
As some of you may remember, I was having problems with my Starboard gearbox. It was slow to engage, not just 1st thing after starting, but all of the time.
On advice, I changed the oil, changed the filter, put an oil pressure gauge on the gearbox, had the hydraulic pump rebuilt...

My symptoms worsened such that, once my engine (and transmission) warmed up to operating temperature, I could NOT go into forward at all. We figured that the piston seals on the flywheel, which operate the forward clutch, were leaking so bad that when the oil warmed up and became thinner, it could not generate enough pressure to engage the forward clutch. Nice theory.

Well, you can remove the transmission (see pictures) but what we found was really bad. The clutch plate was shiny silver with metal shavings everywhere.





So the M20 is currently at Acadian and due back next week. Some facts to remember:

1) Check your input strainer for metal (easier than an oil analysis). If I would have been smarter I would have had this checked out before I purchased the boat since the starboard transmission always had a delay in engaging, even on the survey run.
2) These transmissions will run (at least when cold) when there are major problems.
3) Acadian is the place to go. The basic rebuild price is $1850 (just seals and normal parts). My price went up to $4325 because of having to rebuilt the clutch, plates, replace bearings...
4) If shipping to Acadian, let them arrange and pay for the shipping. They have better rates than you will get unless you are a big time shipper. I thought the $350 (each way) was very reasonable, given the weight and size of the pallet. The speed was also impressive. I called on Monday morning, they picked it up near Baltimore on Monday afternoon and it was at Acadian on Thursday afternoon.
5) Have a lot of extra money because the rebuild cost is only the start. You have to have your mechanic (and his friends) pull and reinstall the transmission.
6) Have even more extra money because, when disassembling the exhaust system and turbochargers you will find other things that need to be replaced. In my case, the PO had 'rebuilt' this engine about 7 years ago but it looks like they either reused the old turbos or had them rebuilt. They need to be replaced....


Hopefully I'll be back on the water soon.

Jon

 

[MikeP]

Hi Jon,

Sorry the tranny turned out to need all that work. The clutch disc reminds me of my drag-racing/engine building days!

I haven't checked the strainer recently but I'll do that when we get back to the marina (we're on the boat at St Michaels at the moment).

I just did a cold start/transmission engagement and, again, it was slow to engage, as opposed to yesterday's 20 minute engine warm up and subsequent immediate engagement. So, again, maybe the service manual's statement re cold water temps/40WT oil solves the "problem." Tomorrow, when we leave St Michaels, I'll do the 20 minute warm up again and see what happens. If the tranny engages promptly, I'll write the whole thing off as a non-issue.