Does anyone know ratio for 5432 w Hurth HBW-100

[Scott Reed]

Does anyone know the reduction ratio for M-40/5432 engine /w Hurth HBW-100 transmission. I ordered a new three bladed prop awhile back, and I think I'm slightly overpitched as I can't get tach beyond 2150-2200 rpm. Below is an exchange I had with the prop folks. I guess most succinctly, is the ratio 1.80:1 or 2:1? I'm hauling for some extensive work, and it'd be a good time to pitch the prop correctly. Many thanks.
Scott Reed
Querencia, E38-200
scott.reed@att.net

ps I suppose I could release compression on engine, engage the transmission, crawl into aft cabin, snake into the small space and manually turn the engine shaft exactly one revolution whilst measuring the transmission shaft response. But that's way too hard for a big fella to do all by himself. Far better to ask you Oracles.

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Sorry for the back and forth. I've conflicting information for reliable sources regarding the specs on the Hurth HBW-100 transmission.

The Universal Engine Manual that came with the Ericson says I have engine model #5432 aka #M-40. Further this manual says I have a Hurth transmission, model # HBW-100, and that the reduction ratio is 2:1.


In checking with two engine, transmission shops affiliated with Universal they both say the reduction ratio is 1.8:1 for this engine (5432), transmission HBW-100.

My inclination is to divide the difference and say the reduction is 1.9:1, which'll bring me within 5% on either side. Can you pitch the new prop based on this compromised 1.9:1 ratio? If I'm not dead on, I'll at least be closer to increasing or decreasing pitch if required.

[footrope]

The PDF that I have of the Marine Diesel Owners Manual that covers the Universal line from the M-12 to the M-50 says the Hurth HBW-100 on the M-40/5432 is 2:1.

[Scott Reed]

Craig,
Many thanks for the information. Very much appreciate it. Though I'm still in a quandary - one of the earlier posts I discovered after my post was sent was from a fellow who actually did what I jokingly described - he relieved the compression, engaged the transmission (presumably in forward LOL), turned the engine shaft through one revolution and measured the output side of the transmission shaft. He said for his 38 the ratio was 1:1.79. So go figure. Looks like I'll have to crawl into tight spaces.
Scott Reed
Querencia, 38-200 #309

[footrope]

Good luck Scott. You have to give some credence to the experts because manuals are wrong all the time.

Since you're doing the measurement I won't add it to my own pre-cruise checklist. But, I think you meant to turn the engine crankshaft one rev and measure the rotation of the transmission output. You can turn the engine from the cabin - all nice and comfy.

I have a three-blade feathering prop and I love it.

[rwthomas1]

FWIW, I did exactly what you described to get an idea of the ratio in my Hurth 100. No need to even relieve compression, the engine will turn over easy enough if you just grab the crankshaft pulley firmly and turn it. Had the wife outside watching the prop. I did two complete engine revolutions which "should" have resulted in one full revolution for the prop for 2 to 1. It did not, prop was a good bit past so the ratio is the 1 to 1.8 option instead. This is easy to do on the hard. RT

[Keith Parcells]

Scott,

ZF bought out Hurth a few years back. That model is now called a ZF-10. It may have been available in either 1.8 or 2.0, so it does pay to check the rotations for yourself. There is a lot of info available on ZF's web site, like this;
http://www.zf.com/corporate/en/company/organization/divisions_business_units/marine_propulsion_systems/matching_tool/matching_tool_large.html

There is an earlier thread here about my transmission woes...I was converting from the HBW50 to a new ZF 10.

Good Luck

[gregdettmer]

I have a 1981 E38, which I am refitting. The Engine and Transmission separated are sitting in my garage and I finally got around to checking the transmission ratio. Based on Marking the input shaft and the output shaft, then rotating the input shaft I found the following:

In Forward I get a ratio of 2:1
In Reverse I get a ratio of 1.8:1

I was surprised by this finding and retested a number of times, with consistent results. I will be opening the transmission soon for Overhaul, and will be able to report in detail on the gears.

[footrope]

I have a 1981 E38, which I am refitting. The Engine and Transmission separated are sitting in my garage and I finally got around to checking the transmission ratio. Based on Marking the input shaft and the output shaft, then rotating the input shaft I found the following:

In Forward I get a ratio of 2:1
In Reverse I get a ratio of 1.8:1

I was surprised by this finding and retested a number of times, with consistent results. I will be opening the transmission soon for Overhaul, and will be able to report in detail on the gears.

Greg, you are the new transmission expert on the board.

The rest of us were only half right. :thepaw: high four

Welcome to Ericsonville.