I am considering a feathering prop and the manufacturer wants to know the reduction gear ratio on the trans. I have a 1995 with a Hurth model HBW100-2.0, Universal engine 35A. The Catalina manual says 2:1 the engine manuals says 1.8:1 or 2:1 depending on which page you look at. The transmission plate says A=1.79 B=1.86. So which ratio do I have? Thanks
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Hurth Transmissions
Pat... I would check with Hurth ZF Industries at 954-581-4040 if u do not get a good answer here.In fact, i would confirm with them any answer u obtain. Their local reps near Annapolis have been very responsive when i have had questions/concerns re my Hurth [150A] transmission. They will put u in contact with your local reps. I have a M-35B with a different transmission than yours. The published gear ratio on the 150A is 2.63:1. Good Luck.
Pat... I would check with Hurth ZF Industries at 954-581-4040 if u do not get a good answer here.In fact, i would confirm with them any answer u obtain. Their local reps near Annapolis have been very responsive when i have had questions/concerns re my Hurth [150A] transmission. They will put u in contact with your local reps. I have a M-35B with a different transmission than yours. The published gear ratio on the 150A is 2.63:1. Good Luck.
Transmission ratio
If you can easily see your prop shaft, you can try what I did. Put the trans in gear & turn the motor by hand (compression released). Count how many engine revolutions it takes for the prop shaft to turn over once. You can come close enough to figure out which one of several possibilities you have on your boat.
If you can easily see your prop shaft, you can try what I did. Put the trans in gear & turn the motor by hand (compression released). Count how many engine revolutions it takes for the prop shaft to turn over once. You can come close enough to figure out which one of several possibilities you have on your boat.
Pat, The plate on your Hurth is the accurate #
When Catalina says 2.0:1, 1.8:1 or whatever that is the "baseline" tranny ratio The number the actual plate is what it is. So your 1.79:1 is also considered 1.8:1 like this one http://www.merequipment.com/product.asp?Product_Id=222557&d_Id=22008&l1=22008&l2= The A is the "forward gear" ratio (A=1.79) and the B is the "reverse gear" which is often not listed when talking about the gearing of a tranny B=1.86 Here is a brochure on all the gearing for a HBW100 https://myeporia.eporia.com/resources/company_122/ZF_10_M.pdf BTW the Hurth Tranny is now made by ZF marine now and calle a "ZF10M" http://zf-marine.com/ZFR/Transmissions/index.cfm?PID=AAB&DS=Description&GN=ZF_10_M Just as an FYI My 1999 C36 MKII with an M35B engine also has a HBW100-2.0, and The transmission plate says A=1.79 B=1.86 allsail - Interesting - What Boat & year do you have that has a HBW150 tranny ?
When Catalina says 2.0:1, 1.8:1 or whatever that is the "baseline" tranny ratio The number the actual plate is what it is. So your 1.79:1 is also considered 1.8:1 like this one http://www.merequipment.com/product.asp?Product_Id=222557&d_Id=22008&l1=22008&l2= The A is the "forward gear" ratio (A=1.79) and the B is the "reverse gear" which is often not listed when talking about the gearing of a tranny B=1.86 Here is a brochure on all the gearing for a HBW100 https://myeporia.eporia.com/resources/company_122/ZF_10_M.pdf BTW the Hurth Tranny is now made by ZF marine now and calle a "ZF10M" http://zf-marine.com/ZFR/Transmissions/index.cfm?PID=AAB&DS=Description&GN=ZF_10_M Just as an FYI My 1999 C36 MKII with an M35B engine also has a HBW100-2.0, and The transmission plate says A=1.79 B=1.86 allsail - Interesting - What Boat & year do you have that has a HBW150 tranny ?
The plate on the transmission is correct
Tom S. is absolutely correct in what he is saying..the transmission plate is the source for the actual ratio, never mind what the manual says...you have what is considered a 1.8:1 transmission. Some ZF transmissions can be run in either direction (to deal with counterotating propellers on dual engine powerboats), simply by shifting them into the A or B position..in other words, they run as well in the "reverse" direction as the normal "forward" direction... go to www.boatdiesel.com and look at the ZF and Hurth transmission information or look at www.foley.com...you will find out a lot about your transmission..
Tom S. is absolutely correct in what he is saying..the transmission plate is the source for the actual ratio, never mind what the manual says...you have what is considered a 1.8:1 transmission. Some ZF transmissions can be run in either direction (to deal with counterotating propellers on dual engine powerboats), simply by shifting them into the A or B position..in other words, they run as well in the "reverse" direction as the normal "forward" direction... go to www.boatdiesel.com and look at the ZF and Hurth transmission information or look at www.foley.com...you will find out a lot about your transmission..
Catalina 36 is backward
The Hurth 100 transmission uses what Hurth calls Back as forward. This means that you want to use the Back number to give to the propeller manufacturer. This is also why many Hurth 100 transmissions clatter at low rpm in "Forward" when installed in a Catalina 36. They evidently were designed for use with Left hand propellers and have been declared useable in either derection rather than designed for use in either direction.
The Hurth 100 transmission uses what Hurth calls Back as forward. This means that you want to use the Back number to give to the propeller manufacturer. This is also why many Hurth 100 transmissions clatter at low rpm in "Forward" when installed in a Catalina 36. They evidently were designed for use with Left hand propellers and have been declared useable in either derection rather than designed for use in either direction.
From all I know that is not why the tranny
sometimes clatters. Everything I know & researched (and have since solved on my boat) shows that clattering comes from the springs on the low end damping plates they put in there. So if people only hear the "clatter" (sounds like a coffee can with pebbles in it) at low speed RPM's its almost always the spring type damping plate. If once the torque and speed of the engine is increased a bit the clatter goes away its because the springs are now under compression. Here is some info from some marine transmission website I have found in the past - MER website ( http://www.merequipment.com/Frequently%20Asked%20Questions/gearclatter.htm ) : "Measures against idle clatter" Idle gear clatter cannot be influenced by means of the transmission. More often than not, a suitable dampening coupling is the solution. There are many dampener manufacturers and varying dampener qualities. Some work better than others. If your engine is equipped with a spring type dampener, this particular type of dampener is at the lower end of dampener quality. You may want to upgrade to a better dampener. Everyone I have ever talked to says the Polimer (not plastic) R&D damper plates are far superior. This explains them http://www.flexible-coupling.com/r-and-d-marine-damper-plates.html I have replaced it with the R&D and many other people and they are all much happier -- You won't have to worry as much about that "pebbles in a can rattle" sound that you get in low gear.
sometimes clatters. Everything I know & researched (and have since solved on my boat) shows that clattering comes from the springs on the low end damping plates they put in there. So if people only hear the "clatter" (sounds like a coffee can with pebbles in it) at low speed RPM's its almost always the spring type damping plate. If once the torque and speed of the engine is increased a bit the clatter goes away its because the springs are now under compression. Here is some info from some marine transmission website I have found in the past - MER website ( http://www.merequipment.com/Frequently%20Asked%20Questions/gearclatter.htm ) : "Measures against idle clatter" Idle gear clatter cannot be influenced by means of the transmission. More often than not, a suitable dampening coupling is the solution. There are many dampener manufacturers and varying dampener qualities. Some work better than others. If your engine is equipped with a spring type dampener, this particular type of dampener is at the lower end of dampener quality. You may want to upgrade to a better dampener. Everyone I have ever talked to says the Polimer (not plastic) R&D damper plates are far superior. This explains them http://www.flexible-coupling.com/r-and-d-marine-damper-plates.html I have replaced it with the R&D and many other people and they are all much happier -- You won't have to worry as much about that "pebbles in a can rattle" sound that you get in low gear.
To Tom S...right about the clatter
I have a powerboat with a 210hp Cummings turbo Diesel and a Hurth (ZF) 630 1.56 transmission in it....clatters terribly at 800 rpm when in forward or reverse...as soon as it gets to 900 rpm ( a little load on the propeller, the clatter vanishes, not to return until rpm drops below 800 again...My Cummins maintenance manual even says that the clatter is "normal" as long as it goes away as rpm is advanced....hard to believe its "normal" when you hear it, but evidently this boat has sounded like that since 1990 and is still operating fine... www.boatdiesel.com is a wealth of information on this subject...just search "ZF transmission clatter" or "ZF gear noise" and you will see just how many people have this same situation..BoatDiesel costs $25/yr to join, but is well worth it if you are maintaining or interested in Diesel engines....as Tom S. said, a new drive damper is the only solution, which means you have to split the marine gear (transmission) from the engine and put in the damper plate...about a $400 part on the Cummins...I dont' know if they are made in the rubber block (quiet) style for smaller engines...Tom S's. web site may show that. the noise doesn't seem to be any different in forward or reverse, just the amount of load on the propeller shaft makes the difference...
I have a powerboat with a 210hp Cummings turbo Diesel and a Hurth (ZF) 630 1.56 transmission in it....clatters terribly at 800 rpm when in forward or reverse...as soon as it gets to 900 rpm ( a little load on the propeller, the clatter vanishes, not to return until rpm drops below 800 again...My Cummins maintenance manual even says that the clatter is "normal" as long as it goes away as rpm is advanced....hard to believe its "normal" when you hear it, but evidently this boat has sounded like that since 1990 and is still operating fine... www.boatdiesel.com is a wealth of information on this subject...just search "ZF transmission clatter" or "ZF gear noise" and you will see just how many people have this same situation..BoatDiesel costs $25/yr to join, but is well worth it if you are maintaining or interested in Diesel engines....as Tom S. said, a new drive damper is the only solution, which means you have to split the marine gear (transmission) from the engine and put in the damper plate...about a $400 part on the Cummins...I dont' know if they are made in the rubber block (quiet) style for smaller engines...Tom S's. web site may show that. the noise doesn't seem to be any different in forward or reverse, just the amount of load on the propeller shaft makes the difference...
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