Tranny burning up (longish)

[Tropic Cat]

Adam and Pat, the link I posted on the ebay unit is currently at $75.00

Rick in Florida

[AdamY]

I thought the ZF12 was thereplacement for the KBW10

I need to check the gear ration and email the ebayer to find out for sure if it is the right one.

[AdamY]

I dont think it is the same transmission, the shift lever on mine is on the starboard side and that one has it aport.

Also, I have to wonder if buying a used one is any better than rebuilding the one I have. Kind of fno way to know how new/good this one is.

Oh well, looks like it wont sell and he will relist anyway.

[DeepFrz]

Adam, have you checked the transmission ratings on the ZF site?

There are 4 different ratings, Pleasure (which looks like it's for getting in and out of slips), Light Duty, Medium and Commercial. They have the numbers there so you could work out what your transmission installation rating is. It might be that you will just keep going through transmissions if you replace it with the same.

My apologies if you have checked this out before.

http://zf-marine.com/ZFR/Transmissio...ex.cfm?PID=AAC



Deep

[AdamY]

okay a few thoughts I would like to run by you folks...

I would love to hear opinions about the suitability of the KBW10/HBW10/ZF 12 trannys for long distance ocean cruising. I am hearing some things from ppl via email that isnt inspiring confidence in me in even a brand new ZF12.

The other issue came up tonight at a cruiser's happy hour here in Ensenada and that is one of prop size/pitch being the possible culprit.

The previous owner of Estrella did a terrible job repowering, not even replacing the shaft when it was oviously needed. This leads me to believe that the prop is almost certainly orig. equipment.

It used to be driven by a Volvo 37hp engine and is now driven by a Yanmar 20hp engine. It is a large 18"X12 fixed two blade prop and this trip is really the first time it has been run for 1100 miles in a row. I am told that the correct prop will see me able to run the engine at it's max rated RPM of 3400 and that the fact that I could only get 2800 out of it before would indicate that I am over propped. The theory being this overpropping stressed the tranny and burned up the cluch. If this is the case a new ZF would burn up in the next 1000 miles with this prop.

If this is the case I would be inclined to rebuild the tranny (or have it done) and get the correct prop.

Any thoughts?

is the ZF/KBW10 a POS that has no business ocean sailing?

could my prop be burning up my clutch?

Thanks in advance?

[never monday]

The rules of thumb I work with would point tword a 18x9 or 16x12 to get your engine speed back up to where it belongs. Yes I could see the extra drag from the prop doing damage to a weak trans. I've not had many problems from either of thoes gears. There are many KBW10's out there in IP's as well as others. That gear was also used behind the 3HM and 3HM35F.
At 16,000 lbs of displacement, your underpowered with 20hp. My guess is the PO might have been trying to get the speed with it over proped. What was the exhaust smoke like? heavy? light? color? transom mustache? What ratio is in your box? look on the plate for this one.

[AdamY]

Originally Posted by never monday

The rules of thumb I work with would point tword a 18x9 or 16x12 to get your engine speed back up to where it belongs. Yes I could see the extra drag from the prop doing damage to a weak trans. I've not had many problems from either of thoes gears. There are many KBW10's out there in IP's as well as others. That gear was also used behind the 3HM and 3HM35F.
At 16,000 lbs of displacement, your underpowered with 20hp. My guess is the PO might have been trying to get the speed with it over proped. What was the exhaust smoke like? heavy? light? color? transom mustache? What ratio is in your box? look on the plate for this one.

Actually Estrella is closer to 20k lbs all loaded down. I figured the Yanmar was on the low end but repowering isnt an option, I would rather just have a reliable underpowered motor than repower which would be like taking our meager cruising kitty and decimating it. We could repower but we would have to go home and back to work immediately ;-)

I dont know the ratio off the top of my head, I regret not writing it down when I had it out last time as it is very hard to read where it is now but I suspect the prop is excessive but to think the previous owner did anything intentionally is giving him too much credit.

Speed was up with the big prop though as we have been motoring most of this trip around 1800 RPMs and getting a consistend 4-4.5 knots of speed out of that little Yanmar.

Before we left there was no smoke at all in the exhaust except when I started her up and that I suspect was just from the flooded unburnt diesel blowing out of the engine from initial start up. But lately it has been a little smokier, the smoke is light though.

There is a good amount of soot around the exhaust (I assume this is av"transom moustache") but we have been using the engine to charge the batteries when we're on the hook which along with motoring at less than full bore builds up soot deposits in the exhaust and when I cranked her up to full power under load (intentionally to clean out the soot from running slow) a LOT of soot would blow out leaving trails of black water behind us.

That said, another recent development since we left to cruise full time is the fresh water in the heat exchanger is scummy.There is zero water in the oil so I doubt it is letting crank case oil in, but still have no idea why there is a smalll layer of scummy oilish water in the surface of the coolant. I flushed it out in San Diego but it came right back.

In any case, If I need a new prop, perhaps I would be better off rebuilding and then being a bit more purist than I have been and sailing more. The motor is underpowered but should easly get us into and out of ports, just might be she is insufficient to actually motor for days on end?

thanks again for all your guidance in this matter, I hope to have a solution sorted out this week so I can implement it and get back to cruising ;-)

[DeepFrz]

Although the information on the ZF web site takes some interpretation, it appears that if you get your prop sized properly the ZF-12 should be okay for continuous duty. The ZF-10 is undersized for a cruising boat with 20 hp / 2 cylinder though. I don't know if the HBW-10 is equiv. to a ZF-10 or ZF-12.

Something that you need to take into consideration when specing the transmission is the derating of the power handling capability of the transmission due to a 2 cylinder engine (20 percent). I would also suggest that you have a temperature gauge installed and to keep an eye on that when motoring.

The problem with a lot of boats is thier equipment is sized for pleasure rating. A cruising boat should be set up for continuous duty rating. As you found out, an 1100 mile cruise under power is "continuous duty", no matter what the hrs. per year spec is. The ratings also state "changes of power settings" and "intermittant running", although they do not elaborate on those phrases. ZF also states that if you don't have the "proper" monitoring equipment installed they won't take responsibility and state that you should contact ZF for clarification.

[never monday]

Originally Posted by AdamY

when I cranked her up to full power under load (intentionally to clean out the soot from running slow) a LOT of soot would blow out leaving trails of black water behind us.

That's a sure sign of being over proped. 4.5kts at 1800 is also alot fast for that speed. I could easily see 2.5 or max 3 at that speed.
I think the 20 will do you fine. You'll need to accept a max speed of 5kts ish. I don't think there is alot of hope for getting near hull speed at 20hp and 20K lbs.

[Alan Wheeler]

Pats spot on. I also calculate 18x8-9 depending on actual ratio of box.

[never monday]

Adam,
I assume you have the 2.14 ratio in that trans?
An alternative I've thought about is. Change to a new trans in the 3:1 area. This will allow a large prop to spin more efficiently at the engine speed you need. I'm looking for a trans for you today and have one lead sofar.

[AdamY]

I assume going with a 3:1 tranny would have the benefit of not requiring a reprop? This would be beneficial as this water is both cold and disgusting. I am shopping for a wetsuit anyway but if I end up repropping I will save myself a wetsuit worth of money by doing it myself with a snorkel.

I'll try and angle a mirror in there today and get the actual ratiio thouugh 2.14 sounds familiar.

I will resume my search today as well, though I recall the ZF-12 doesnt come in a 3:1.

Thanks for your help, Pat I'll look forward to hearing what you find.

Cheers,

[never monday]

Adam,
The best I can come up with is a 2.5/1 gear. You might not need to reprop. We'll need to see waht the perforamnce is after the change. If you go this route. To keep as much cash in your pocket as posible I'd consider rebuilding what you have and reproping. Counter to that with the 2.14 gear you could end up back in this again.
With your full keel and heavy weight a smaller gear ratio will be a better option. Taking pitch out of your prop isn't a great idea at the 12" you have. Next would be taking diameter away, if you get to small the keel will shadow the prop and you'll have no performance.

[AdamY]

Originally Posted by never monday

Adam,
The best I can come up with is a 2.5/1 gear. You might not need to reprop. We'll need to see waht the perforamnce is after the change. If you go this route. To keep as much cash in your pocket as posible I'd consider rebuilding what you have and reproping. Counter to that with the 2.14 gear you could end up back in this again.
With your full keel and heavy weight a smaller gear ratio will be a better option. Taking pitch out of your prop isn't a great idea at the 12" you have. Next would be taking diameter away, if you get to small the keel will shadow the prop and you'll have no performance.

Okay so it sounds like there is no really great option. a 3:1 gear is ideal but unavailable. Rebuilding will likely land me in the same place as I am now if I do not reprop, however I will suffer if I decrease pitch or diameter.

What about rebuilding this tranny and buying something with adjustable pitch for the prop. It would cost as much as a new tranny to put a Kiwi Prop on but with the Kiwi I would end up with a 3 blade adjustable pitch prop. This way I can go with less pitch and if it is crippling I can fine tune it to the ideal thrust to tranny-effort ratio. Is a 3 blade prop, fixed or otherwise (which would be naturally a smaller diameter) worthwhile to consider as a middle ground between pitch loss and tranny burn?

Like most things boat related I am certain there will be no ideal solution and what I can hope for is a compromise at best. Still it could be worse, I could be stuck on the Oregon coast in a gale getting pissed on ;-)

Thanks again for the attention,

[never monday]

All this brain power in one place, I'm scared.
Go 3 plade adjustable, get more BSA for less dia? HUm...I gotta chew on that one.