Perkins 4-154 and the Mystery Transmission

[brian and clare]

Hi Folks, I have had some help identifying this Transmission as a Hurth, but now I want to zone in. The photo I was given my the marina guy was a bit dark but through the majic of photoshop I lightened it up for better identification. My Best guess is that this is a Hurth ZF25M transmission, which I deduced from looking online

TAD for ZF 25 M Marine Transmissions, ZF Marine Transmissions, ZF Marine Transmissions, ZF Hurth Transmissions

at pictures of transmissions. The photo of the one in the boat is attached. My uncertainty comes because of the attachment to the back of the engine. I think it has the round attachment, but some of the boxes are shown without the round attachment? Anyone an expert on the hurths?

Thanks folks

[never monday]

the square (ish) trans bolts to a round bell housing adapter. I'd guess an SAE #3

[beetle]

What Pat said.

I'm no expert on Hurth's, but I've pulled and reinstalled them for servicing at a mechanics shop.

The transmission uses an adapter plate to connect the transmission to the back of the motor - that's the large round attachment plate you describe. Behind that plate is a damper plate attached to the motor, and the damper accepts a splined shaft coming out of the Hurth - all power transfers through the damper. If you're planning to pull the transmission is usually not difficult provided you have clearance to get the tools in place. Plan on unbolting the adapter plate from the motor, slide the transmission spline out of the damper plate, and then you can set the unit on a bench and unbolt the adapter plate from the transmission. Hopefully the prop shaft can be slide aft to provide clearance.

While the transmission's off replace the damper plate at the same time - it's a bummer to have to pull the transmission a second time just to replace the damper.

The transmissions are suprisingly heavy and it is much easier to do the pull/install with two people than on your own. One person holds the transmission and the other works the bolts. If you are replacing a transmission retain the adapter plate - it is not part of the transmission.

- beetle

[S/V Antares]

Yup, Thats a Hurth (Now ZF) You are lucky that it is attached with the adapter. It makes it easy to get off. The Trans is attached to the adapter with (6) 8mm or 10mm bolts from the inside. You will see them when you take the adapter plate and trans out. My access to the back of the engine is poor. My wife replaced my trans last month. She fits!

[Alan Wheeler]

What Brian is trying to determin is which model is this box. We have determined it is a Hurth of the ZF range, but is it a 15, 25 or what. I am assuming it is a 25. Only by the engine power on the front end of it. Here is the reason why we are trying to find as much information as possible.
The boat is not in NZ. It has been left up in the Islands because the box ceased working. Brain needs to either, take parts over and fix the box, or better yet, take a whole new working box over and replace the current one. He has no way of getting the parts or replacement box once over there. He will also have limited time to do the job once there. I think the replacement box is the best approach, if one can be found. But this brings another question if anyone can help. Does the input shaft and spline change between models of box. As in the 15 or 25 or what have you? He doesn't want to take over another box only to find it doesn't slip in.

[beetle]

Originally Posted by Alan Wheeler

What Brian is trying to determin is which model is this box. We have determined it is a Hurth of the ZF range, but is it a 15, 25 or what. I am assuming it is a 25. Only by the engine power on the front end of it. Here is the reason why we are trying to find as much information as possible.
The boat is not in NZ. It has been left up in the Islands because the box ceased working. Brain needs to either, take parts over and fix the box, or better yet, take a whole new working box over and replace the current one. He has no way of getting the parts or replacement box once over there. He will also have limited time to do the job once there. I think the replacement box is the best approach, if one can be found. But this brings another question if anyone can help. Does the input shaft and spline change between models of box. As in the 15 or 25 or what have you? He doesn't want to take over another box only to find it doesn't slip in.

Is it possible to have the transmission removed from the boat and shipped to Brian? This would allow Brian all opportunity to repair/rebuild/replace the transmission and then he can take the new, working, guaranteed-correct unit with him to the Islands and it will fit.

- beetle

[donradcliffe]

Go to Simplicity Marine Drives - Hurth/ZF Transmissions & Prices and download the dimensions for the various Hurth models, then go measure.

[Alan Wheeler]

Maybe, only Brian can answer that one. I don't know if the island has a mechanical yard. I think that may be part of the problem.

Don, we can't go measure, that's the problem.

[brian and clare]

Hi,

I tried asking them to pull it off and repair. They wont have any part of pulling it off for me. It is apparently too rusty and they dont want to break anything they say. I am thinking that if I get a new one ZF should be able to get me the right spline for a perkins (Standard for each brand of engine I hope?). The 25 M Model in the link provided looks like the one I am dealing with. I suppose if it does not line up correctly with the shaft I could just adjust with the engine mount height?

[brian and clare]

FYI-

I just sent an e-mail to the hurth Guy in the link asking about the splines. From my reading online and other peoples advice, I understand it this way:

The splined shaft goes into the damper plate and the damper plate bolts onto the flywheel right? So does the spline have to match the damper plate? Does the damper plate have enough holes in it to match any engine flywheel? I read on another site that it is best to replace teh damper plate with the transmission.

OK My next question (driven my my desire to not buy a new transmission) is what happens if the damper plate breaks? Can it break? Could that possibly be the reason my transmission does not work?

Thanks
Brian

[beetle]

Originally Posted by brian and clare

Hi,

I tried asking them to pull it off and repair. They wont have any part of pulling it off for me. It is apparently too rusty and they dont want to break anything they say. I am thinking that if I get a new one ZF should be able to get me the right spline for a perkins (Standard for each brand of engine I hope?). The 25 M Model in the link provided looks like the one I am dealing with. I suppose if it does not line up correctly with the shaft I could just adjust with the engine mount height?

Given that the local yard won't pull the transmission, I would start from the other direction: which Perkins is attached to the transmission and what is the diameter of the prop shaft, the prop dimensions, displacement and LWL of boat? Perhaps what the transmission *ought* to be can be determined from that information, regardless of model the current transmission is. If this is an original engine, is the builder available to talk to?

There are several items to consider: the reduction gearing in the transmission (most Hurth's have various reductions to choose from), the offset of the shaft through the transmission (even a straight-through transmission has a vertical offset), and the adapter plate - the adapter plates are intended to fit between a specific transmission and a specific motor. If you appear with the incorrect transmission the plate won't fit the transmission, the splined shaft won't mate with the damper, and you're out of luck.

If there's a ton of money available simply purchasing several different transmissions might allow decisions to be made on the spot, but most of us (me included) don't have that option

- beetle

[beetle]

Originally Posted by brian and clare

The splined shaft goes into the damper plate and the damper plate bolts onto the flywheel right?

Yes.

Originally Posted by brian and clare

So does the spline have to match the damper plate?

Yes.

Originally Posted by brian and clare

Does the damper plate have enough holes in it to match any engine flywheel?

No. The damper plate is mated to a specific motor.

Originally Posted by brian and clare

OK My next question (driven my my desire to not buy a new transmission) is what happens if the damper plate breaks? Can it break? Could that possibly be the reason my transmission does not work?

Possibly, depending upon what your transmission is doing. Can you describe precisely what the failure mode was?

If what you note is that NOTHING happens when you force the transmission into gear (e.g., the prop shaft does not rotate even though the engine is running and the transmission is turning), it could be the clutch plates in the transmission have worn smooth and are slipping - this will be noticeable by the transmission turning steaming hot - the slipping plates generate an enormous amount of heat and you won't be able to touch the transmission even briefly when the motor has been running at normal RPMs for a couple of minutes. Note that Hurth's run hot but not so hot that they will burn you.

Usually the forward and reverse clutch plates do not fail simultaneously as most folks don't motor around backwards half the time. If the transmission won't rotate the shaft in forward, try putting it into reverse; if the prop magically starts turning and transmission cools off a bit then you've lost the forward clutch plates - time for a transmission rebuild (or at the very least replace the forward clutch plates).

Damper plate failure is usually accompanied by exotic sounds of rattling metal and other nasty bits.

- beetle

[brian and clare]

Hi again,

Failure mode was as below:

Originally shift into gear and there is a slow hesitation before clunking into engagement.

Move on to really long hesistation, and having to goose throttle resulting in it clucking into gear at half power which is nerve wracking and voilent.

Then having to shift a few times to get it to work at all, and any tap of the throttle would make it fall out of gear.

Eventually shifting produced nothing. Shifted by hand without the cable taken off , and still nada. Reverse worked still though. No clanging and banging ever happened.

Ended up with absolutely no response to foreword shift.

Lets just say that tons of money is not really in the cards. If our life didnt depend on it I would put on a backward prop and use reverse instead. This will likey be a 20% interest Visa purchase paid off over the next 20 years.

[Alan Wheeler]

It is certainly not the dampner plate Brian. As Bettle stated, you woudl lose all drive compleatly and instantly. It is certainly internal of the box.

Bettle, can you absolutley confirm that there are both a seperate fwd and rev clutch??? If yes, then I am certain it will be the fwd clutch that has failed. But from a parts brakedown, I did not see a clutch itemized on the diagram, let alone two of them. Maybe there is another page to that parts breakdown.

[Alan Wheeler]

Oh here is an important part to the discussion. From the picture Brian has given, this box looks most likely the 25M. The M being the important part. This is the Mechanical box not the hydraulic box. The hydraulic box has clutch packs, but I don't believe the mechanical one does, unless anyone can say otherwise.