Need help selecting a new transmission.

[ben2go]

Through research, I have narrowed my transmission choices down to two that will work the Beta 38 engine going in my boat. The two units are the PRM Newage PRM125 and the Technodrive/Twin-disc TMC-60-A. Both of these units are very similar in design and operate the same. Both are cone clutch style transmissions.



Let's start with the PRM unit. The PRM125 is an updated and upgraded version of the PRM120. I will have to cut down and angle my engine beds along with angling the engine up at 7 to 8 degrees or add a V-drive and reverse mount the engine. It will barely fit under the hatch. I may be forced to use solid engine mounts to get the engine low enough in the hull to use the PRM trans. I found this transmission has a 1500 hr rating between refreshes. It's rated for 5000 rpm input. It will take everything my engine has at 38hp and 3600 rpm. I also have a full shop service manual for this transmission. The UK canal cruisers love them. They brag about how much abuse and neglect they can take.


The Technodive/Twin-disc unit on the surface seems to be a perfect choice. It specs out just a little under the PRM125 but more than capable of handling my engine and boat. The one major plus is the TMC-60-A has a built-in 7 degree down angle. I couldn't find a recommended refresh time frame. Only a service guideline. I found a few naysayers on the TMC trans but no mention of a specific model number. This transmission would greatly simplify my driveline install, not that it would add much complexity to install the other set up. I would just have to spend more time measuring twice and cutting once to get the angle correct on the engine beds.


What do you guys think? Any experience with either of these transmissions? I'm leaning toward the Techno/T-D because of ease of installation, but it's hard to ignore the PRM's reputation of being drug through the mud in the UK canal system in narrow boats.

 

[FF]

I love Twin Disc

I have found the commercial grade equipment is frequently a better choice.

Purchase the repair manual first,and look carefully for any surprises.

 

[twistedtree]

To me, the prospect of rigid engine mounts would be a show stopper right there.


And the 1500 hour refresh is a red flag. That's barely broken in, and it's time for a "refresh"? I would expect something more like 10,000 to 20,000 hrs.


And 7-8 deg engine angle would be a yellow flag. Check what Kubota allows in a stationary application. 10-12 deg seems to be a common absolute limit.



And last, if you are operating principally in the US, I think you will find support for the TD gear more readily available.


I think the only question I would have is to vet out the mumblings you have heard about the TMC.

 

[O C Diver]

I agree with TT about not hard mounting the engine. Without looking, I'm guessing the engine is a 4 cylinder without counter rotating balance shafts. The vibration would be miserable at low RPMs and still present at mid range and higher.

ZF doesn't offer anything in that range with a down angle? Went and looked at Beta's site. It's unclear but it appears that if you run the TM-60 in reverse for forward propulsion, they want you to use a gear oil cooler. Does that mean no gear oil cooler normally? Didn't see oil cooler hoses in the engine drawing. Can't imagine a boat transmission without an oil cooler. If the oil cooler is an option, I would want it added.

Ted

 

[Ski in NC]

Not a fan of mechanical shift transmissions as they tend to "bang" into gear, rattle at low rpm and also tend to wear faster than a hydraulic gear. Problem is, at this low hp mechanical may be all that is available. Unless you spec a hydraulic gear much larger than needed for the hp.

I'd look for the smallest hydraulic gear on the market and see what you can find.

Most marine engines sold in this hp range are for sailboats, and they tend to tolerate noisy gears as the engine is (should be) used only rarely.

And yes, no way do you want solid mounts. It will rattle the crap out of your boat.

 

[TDunn]

What gear ratio do you want? The has the most options. I would choose by a combination of dimensions and desired gear ratio noting that gear ratio will effect you choice of prop. The Beta web site lists the standard options as: TMC 60 (standard = lowest cost), TMC 60A (down angle), PRM 120 and ZF 15IV (V-drive). All of those are mated to the engine by Beta. Their web site has dimensional drawings and lists available gear ratios .

 

[ben2go]

I love Twin Disc

I have found the commercial grade equipment is frequently a better choice.

Purchase the repair manual first,and look carefully for any surprises.

I haven't seen anything commercial that would work plus commercial usually means a premium price tag.


I've been trying to locate a service manual but no luck. I may have to do something outrageous like make a phone call or send an email. LOL

To me, the prospect of rigid engine mounts would be a show stopper right there.
I agree. I used to work on ski boats with hard mounted inboard gas engines. Felt like standing on a paint shaker at certain RPMs.



And the 1500 hour refresh is a red flag. That's barely broken in, and it's time for a "refresh"? I would expect something more like 10,000 to 20,000 hrs.
I may have red that wrong. I'm trying to find where I read the 1500hr interval.



And 7-8 deg engine angle would be a yellow flag. Check what Kubota allows in a stationary application. 10-12 deg seems to be a common absolute limit.

15 degrees is the max limit using a standard automotive style sump. The shallow sump is less but I forget how much, I think 9 degrees. I only need enough for a 7 degree shaft angle. I still prefer a straight mounted engine. Let the transmission do the work.





And last, if you are operating principally in the US, I think you will find support for the TD gear more readily available.
I was surprised to find that the PRM is easy to get parts for in the US. There is even a kit that isn't much money that can be purchased and cared as a spares kit.



I think the only question I would have is to vet out the mumblings you have heard about the TMC.

I would have to sign up for even more forums to grill the TMC naysayers.

I agree with TT about not hard mounting the engine. Without looking, I'm guessing the engine is a 4 cylinder without counter rotating balance shafts. The vibration would be miserable at low RPMs and still present at mid range and higher.

ZF doesn't offer anything in that range with a down angle? Went and looked at Beta's site. It's unclear but it appears that if you run the TM-60 in reverse for forward propulsion, they want you to use a gear oil cooler. Does that mean no gear oil cooler normally? Didn't see oil cooler hoses in the engine drawing. Can't imagine a boat transmission without an oil cooler. If the oil cooler is an option, I would want it added.

Ted

The engine is a V1505 Kubota four-cylinder without a turbo and 35-38hp depending on who you ask, Kubota or Beta. I'm not sure if it has balance shafts. As smooth as they run, they either have balance shaft or Kubota took the time to balance everything internally and use a harmonic balancer on the crankshaft. Also, that big flywheel helps hold down some vibrations.



Neither of the transmissions I am considering use an oil cooler when runing standard rotation, and I will. I'll have a temp guage for the transmission though. If I see high temps, I'll add a cooler.

Not a fan of mechanical shift transmissions as they tend to "bang" into gear, rattle at low rpm and also tend to wear faster than a hydraulic gear. Problem is, at this low hp mechanical may be all that is available. Unless you spec a hydraulic gear much larger than needed for the hp.

I'd look for the smallest hydraulic gear on the market and see what you can find.

Most marine engines sold in this hp range are for sailboats, and they tend to tolerate noisy gears as the engine is (should be) used only rarely.

And yes, no way do you want solid mounts. It will rattle the crap out of your boat.

I am aware of the noises from a mechanical transmission. I'm not a fan but willing to live with some noise. It will be buried in the blige and behind the rear cabin wall. There will be bulk heads around the engine with sound deadening.



With 38hp and I think 16hp continuous at 1800rpm, wear shouldn't be to bad.

What gear ratio do you want? The has the most options. I would choose by a combination of dimensions and desired gear ratio noting that gear ratio will effect you choice of prop. The Beta web site lists the standard options as: TMC 60 (standard = lowest cost), TMC 60A (down angle), PRM 120 and ZF 15IV (V-drive). All of those are mated to the engine by Beta. Their web site has dimensional drawings and lists available gear ratios .

2.45 or 2.50 to 1 will allow me to run a 16 to 18-inch prop. I don't know exact prop size until I get the keel built and laid in. I could extend the keel a few inches aft to allow for a larger prop. I have looked at that on the plans. If I set up my shaft the way I want, I may be able to squeeze in an 18-inch prop with just enough hull clearance to prevent cavitation.



The PRM120 is no longer made and Beta hasn't updated their info on that. In 2016 the PRM 125 replaced the 120 and is supposed to be an upgrade. I didn't research the 120 enough to know what was upgraded.






A final note here. Many will think I'm a bit early with the transmission decision. When I lay the frames on the stong back and run my chine logs and coamings, I'll have to install the engine beds, then the keel, so the shaft tube can be cut in at the right place and angle.

 

[FF]

"I've been trying to locate a service manual but no luck. I may have to do something outrageous like make a phone call or send an email. LOL"

You might try the folks that are converting the engine , as the sale requires a happy buyer to part with some cash.
RPM is no big deal with these fine engines.

Might the 3 cylinder version with a deeper reduction gear create the 18 hp needed at cruise , and solve the 4 cylinder vibration hassle? Lighter too!

https://betamarineengines.com/files/8513/9717/3182/beta-30-graph.pdf

This graph shows 18 hp at under 1800 rpm so a tranny that would allow say 2200 rpm at normal cruise shaft rpm might be just the ticket?

 

[AusCan]

Hey Ben2go,

ZF make a few gearboxes that may suit your needs. The ZF-15MA and ZF-25MA are 8 degree downangle hydraulic gearboxes. I repowered my boat with a 42hp Vetus paired with the ZF-25MA. The Vetus dealer suggested the 15MA would do the job, but I decided to go a size up since I had the space and there wasn't much difference in price. The 8 degree downangle allowed me to get the engine within a couple degrees of being level.

Either one is available in a range of ratios, from about 1.875 to 2.632:1. The only disadvantage I can see with the downangle gearboxes is they tend to end up with a smaller capacity oil crankcase in comparison to the standard straight box.

As you are aware, there needs to be some good measurements and planning into your engine bed, so its definitely worth deciding on what transmission you'll be using. There are good drawings and manuals for ZF on line. I build a wooden mockup of my engine and transmission to ensure I had the engine mounts aligned properly to get a good shaft alignment. It sure made things work out nicely when I installed the real thing.

 

[Ski in NC]

The ZF 15MA and 25MA are mechanical shift, not hydraulic. Still good gears, but a bit harsh.

Edit: looks like the smallest hyd gear is the ZF 25. Might be a good fit.

 

[ben2go]

Thanks for the input guys. The Beta 38 was chosen due to wanting to run a large 120A+ alternator. I'm still working out the electrical design details. Also, to run 6kts would take 12hp using all the prop calculators I can find around the web.



The transmission comes as a package with the engine. I was wanting to stay with the offerings that Beta has for transmissions. I'm trying to avoid as many snafus as possible.



As far as service manuals. I have located and downloaded all that I can. The others I will have to pay for. No big deal as the $80 to $120 cost is well worth it to know what's going on inside and at least have an idea of what's involved in the event a repair needs to be made off the boat.

I have been in contact with or waiting for responses from the various transmission and engine companies. I didn't know that Kubota had a completely separate engine division in the US. I learn something new every day.

 

[AusCan]

The ZF 15MA and 25MA are mechanical shift, not hydraulic. Still good gears, but a bit harsh.

Edit: looks like the smallest hyd gear is the ZF 25. Might be a good fit.

Your right, Ski (as usual) The "M" designates mechanical shift. The "A" designates the 8 degree downangle.

THE ZF 15A is a bit smaller than the ZF 25A, and they both are available in the down angled version with the hydraulic shift.

 

[FF]

For any engine a great question to the seller is what power can be taken of the front of any engine.

Some lawn equipment runs hyd pumps off the front ,so the output is good.

Most marinizers offer a large number of packages.

I like a stock alt to charge the start batt , as most time it does almost nothing so will not wear out its bearing, so the stock water pump operation is at less risk.

A dual pulley bolt on, can operate a large alt and a water maker or hyd , or refrigeration pump with low loads if installed on either side of the engine.If any fail, the engine can keep operating.

 

[Ski in NC]

Ben- Talk to Beta, many engine packagers will put on the gear of your choice with no fuss.

I think the ZF offerings are such:

ZF 15 M, 15MA are mechanical

ZF 25 M, 25MA are also mechanical

ZF 25, 25A are hydraulic. Looks like their smallest hyd offering. Although their website gave me a headache.

 

[ben2go]

For any engine a great question to the seller is what power can be taken of the front of any engine.

Some lawn equipment runs hyd pumps off the front ,so the output is good.

Most marinizers offer a large number of packages.

I like a stock alt to charge the start batt , as most time it does almost nothing so will not wear out its bearing, so the stock water pump operation is at less risk.

A dual pulley bolt on, can operate a large alt and a water maker or hyd , or refrigeration pump with low loads if installed on either side of the engine.If any fail, the engine can keep operating.

Funny you should mention these points. When I was emailing with Mr. Spira about engine options, I never took into consideration my possible alternator size or prop size. Beta rep led me to water and I finally took a drink. Through research, I have been looking at horsepower versus alternators. I may be undersized with a 38hp engine. The engine alone will get me just over 6.5kts at 3/4 throttle add in a 120-130 amp alternator that may pull as much as 7hp and the continuous 16hp of the 38 drops to 9hp when the alternator is really working. I may end up going to the 50hp it's the same as the 43 and spins at 2800 rpm max where the 38 sings at 3600 rpm max. I believe I would rather hum along at 14-1600 rpm rather than 22-2400 rpm. With the 50hp I could run the ZF25A. My prop size choices expand from 16-18 inches with the 1.9:1 ratio or 18-20 inches with the 2.29:1 ratio. I'm hoping for a larger wheel with less pitch, 17x10.

Ben- Talk to Beta, many engine packagers will put on the gear of your choice with no fuss.

I been in contact with them and will be staying in contact.

 

[Ski in NC]

I too would favor a 50hp at 2800 vs. a 38 at 3600. Your cruise rpm will be a good bit lower. I just don't like the sound of a diesel spinning way over 2000rpm at cruise. Something very pleasant about 1800 for a wide range of engines.

I'll have a look at Beta's offerings.

Edit: Looked at the Beta 43 and 50. Looks like they are the Kubota V2003 and V2203 respectively, although the bore and stroke numbers for the 43 don't match Kubota V2003. Might be a typo or some sort of model change. The 50 does match the V2203. Both are rated at 2800 and would do well with the ZF 25A (hyd) gear.

I have no experience with the above Beta packages, but have been around other Beta's. I found them generally well done, but one gripe is aluminum heat exchanger housing. Where bundle attaches, there can be corrosion on the Al casting. Otherwise, seems like a nice package.

The Kubota engines in my experience have been nothing but rock solid. No direct experience with the V2003/2203, but have a lot of experience with other models. All were good stuff.

These are IDI (indirect inj, aka prechamber) engines, so a little penalty on fuel burn, but way less combustion noise.

Beta seems to use the "Metalastic" soft mounts. Good stuff. YOU DO WANT flexible mounts such as these for this type of engine. Trust me on that.

The four cyl four stroke has two vibe modes: Low idle firing pulses, those get worse as rpm goes down. A rocking motion about the CG. Almost vanishes as you get above about 1000rpm. The other mode is a second order vertical shake at 2x crank speed that shows up somewhere above 1800, and gets progressively worse with higher rpm. Sounds like a buzz. Some larger 4cyl use counter rotating balance shafts in the sump to counter this, but these Kubotas do not have them. Another reason to favor lower rpm 4cyl machines. High rpm buzz can be quite annoying. Soft mounts help, but it will still be noticeable.

 

[ben2go]

I too would favor a 50hp at 2800 vs. a 38 at 3600. Your cruise rpm will be a good bit lower. I just don't like the sound of a diesel spinning way over 2000rpm at cruise. Something very pleasant about 1800 for a wide range of engines.

I'll have a look at Beta's offerings.

I have ran equipment with both high revving diesel and low revving diesel. I much prefered the low revvers. They didn't require hearing protection.

 

[FF]

Our older Volvo MD 3B drives a cast iron refrigeration compressor.

The engine is rated 35HP at 2500RPM.On departure from a 3 day anchorage whatever RPM is set (1600-1800) slowly climbs as the eutetic plates ( 10hp ) get frozen and the batts get charged . No big deal.

Whatever size you choose avoid turbos and inter coolers .

Only boat with Beta 30 I have been aboard wasn't bad ,35 ft heavy sailboat, at 2500 it sounded like an electric motor and there was little vibration.

The heavy hull construction may have helped.

 

[ben2go]

Our older Volvo MD 3B drives a cast iron refrigeration compressor.

The engine is rated 35HP at 2500RPM.On departure from a 3 day anchorage whatever RPM is set (1600-1800) slowly climbs as the eutetic plates ( 10hp ) get frozen and the batts get charged . No big deal.

Whatever size you choose avoid turbos and inter coolers .

Only boat with Beta 30 I have been aboard wasn't bad ,35 ft heavy sailboat, at 2500 it sounded like an electric motor and there was little vibration.

The heavy hull construction may have helped.

Force fed engines are out. In my days as an auto tech, I worked on a lot of them. I'm not a fan of a turbo or supercharger unless it's on someone elses vehicle or boat.



Depending on the boat being compared to. My boat would be considered lightly built as it doesn't have a full keel. It has what I know as a quarter keel. Some refer to it as a skeg.

 

[stubones99]

You could go with a canaline engine (I think it is the same Kubota engine) which has twin alternators standard and can include transmission too.
Canaline 38 Marine Engine – Canaline Engines

Barrus also makes that style engine:
https://www.barrus.co.uk/divisions/marine/diesel/shire/our-products/

If it were me, I would put one of these in there...
https://www.ebay.com/itm/Deutz-F4L9...964149?hash=item2acaf95475:g:AwAAAOSwHodcczjq

The only downside is that it is an industrial engine, not a tractor engine, and that means it lacks the balancer shaft and will have more vibration. The last 4 cylinder I overhauled in the mid-1970s ran for over 50,000 hours, pulling an irrigation pump on a farm. It is air cooled, so you won't need that hole in the boat, just duct in air for it to breathe and blow out the exhaust air somewhere convenient. That model will make about 15hp per cylinder so if 38hp is your target, you could switch to the F3L912 engine. We ran a 3 cylinder tractor pulling a generator (after a major snowfall and the power went out) for over a week, and it averaged about 3 liters per hour at 1800 rpm. During the day, Dad took it around to several farms in the area and ran their chicken house hardware so they didn't have thousands of chickens starving due to lack of food and water. All told, I think we burned about 38 gallons of diesel fuel, shutting the tractor off at midnight each night and cranking it back up at 7 am. Those engines are absolutely bulletproof and tougher than any other engine I've ever been around. If you need hydraulics, there is a gear driven hydraulic gear pump mount on the front left side of the engine and you can piggyback a double pump for separate hydraulic systems.

 

[ben2go]

You could go with a canaline engine (I think it is the same Kubota engine) which has twin alternators standard and can include transmission too.
Canaline 38 Marine Engine – Canaline Engines

Barrus also makes that style engine:
https://www.barrus.co.uk/divisions/marine/diesel/shire/our-products/

If it were me, I would put one of these in there...
https://www.ebay.com/itm/Deutz-F4L9...964149?hash=item2acaf95475:g:AwAAAOSwHodcczjq

The only downside is that it is an industrial engine, not a tractor engine, and that means it lacks the balancer shaft and will have more vibration. The last 4 cylinder I overhauled in the mid-1970s ran for over 50,000 hours, pulling an irrigation pump on a farm. It is air cooled, so you won't need that hole in the boat, just duct in air for it to breathe and blow out the exhaust air somewhere convenient. That model will make about 15hp per cylinder so if 38hp is your target, you could switch to the F3L912 engine. We ran a 3 cylinder tractor pulling a generator (after a major snowfall and the power went out) for over a week, and it averaged about 3 liters per hour at 1800 rpm. During the day, Dad took it around to several farms in the area and ran their chicken house hardware so they didn't have thousands of chickens starving due to lack of food and water. All told, I think we burned about 38 gallons of diesel fuel, shutting the tractor off at midnight each night and cranking it back up at 7 am. Those engines are absolutely bulletproof and tougher than any other engine I've ever been around. If you need hydraulics, there is a gear driven hydraulic gear pump mount on the front left side of the engine and you can piggyback a double pump for separate hydraulic systems.

The first two haven't been EPA certified for sale in the US and may get confiscated by US customs. I had that happen when importing a 140cc Honda monkey bike clone engine.



I looked into the Deutz but it is way too tall and heavy. The Kubota based Beta 50 I have decided to run will be about 8 inches above deck level requiring a small engine box. The deutz would be about 10 inches taller. Currently, I'll only have one underwater thru hole. That will be the opening for the keel cooler. The Deutz would eliminate it. The Deutz is almost 300lbs heavier when comparing the 50hp models.

 

[ben2go]

Getting back to transmissions. I called a few shops that do boat repowers. Most were familiar with Beta. When I described my build and plan to them, most said the TMC 60 A would be their choice over the ZF. The reason being is the mechanical transmission aren't as bad as they used to be for noise and clunky shifting, they don't need oil coolers for my application, and will simplify my install.

 

[Billymc38]

New to group today and saw your post on transmission choices .
I’ve just purchased a kabota v1505 and I’m going to replace my Perkins M30 and would like to know what you did for transmission?
I was planning on taking hurth 100 off of my Perkins hoping it would fit , since I have two of these transmissions woukd run those ti they died and then would like to replace with what worked for you ?
Thdnk you
Billy McGrew
Carolina Beach NC

 

[ben2go]

New to group today and saw your post on transmission choices .
I’ve just purchased a kabota v1505 and I’m going to replace my Perkins M30 and would like to know what you did for transmission?
I was planning on taking hurth 100 off of my Perkins hoping it would fit , since I have two of these transmissions woukd run those ti they died and then would like to replace with what worked for you ?
Thdnk you
Billy McGrew
Carolina Beach NC

Welcome to the forum. I had some health set backs, then covid, and I never was able to get into my projects to sort out a transmission. The hurth may work, I honestly do not know. There's a place in the UK ASAP supply. They may know. They have mated all kinds of stuff to Kubota engines. I'd send them an email and see if they can give you better advice.


https://www.asap-supplies.com/