Reply
 
Thread Tools Display Modes
 
Old 05-12-2016, 11:14 AM   #1
Member
 
City: Long Beach, CA
Country: USA
Vessel Name: Dawn Marie
Vessel Model: 84 35' CHB Trawler
Join Date: Aug 2013
Posts: 7
Gear Ratio

Does anyone know the gear ratio of a Perkins 4.236 85 HP dual engine in a CHB 35? I'm trying to figure out what prop I need.
__________________
Advertisement

CHB RON is offline   Reply With Quote
Old 05-12-2016, 11:20 AM   #2
Guru
 
djmarchand's Avatar
 
City: East Greenwich, RI
Country: USA
Vessel Name: Bella
Vessel Model: Mainship Pilot 34
Join Date: Aug 2012
Posts: 2,881
Even if someone reports the gear ratio in their CHB with that engine, I wouldn't base a prop purchase decision on that info. This was CHB from 30 or so years ago remember.


But you can easily figure the ratio with a phototach. Rev your engine up to about 1,000 rpm and measure the engine rpm and then without changing anything measure the prop shaft rpm. Divide the two to get the ratio.


David
__________________

djmarchand is offline   Reply With Quote
Old 05-12-2016, 11:28 AM   #3
Guru
 
dhays's Avatar
 
City: Gig Harbor
Country: United States
Vessel Name: Kinship
Vessel Model: North Pacific 43
Join Date: May 2015
Posts: 5,090
That info may also be on the transmission somewhere.
__________________
Regards,

Dave
SPOT page
dhays is online now   Reply With Quote
Old 05-12-2016, 01:35 PM   #4
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 3,888
Do Dave's trick, but on both. Lots of BW gears out there with 1.91:1 ratio on one side, 2.10:1 on the other.
Ski in NC is offline   Reply With Quote
Old 06-09-2016, 05:20 AM   #5
Guru
 
Aquabelle's Avatar
 
City: sydney
Country: australia
Vessel Name: Aquabelle
Vessel Model: Ocean Alexander Flushdeck
Join Date: Jun 2012
Posts: 538
Eric.....why did/do they do the different ratios?
Thanks in advance for explaining.
Aquabelle is offline   Reply With Quote
Old 06-09-2016, 09:28 AM   #6
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 3,888
It was a byproduct of getting counter rotation. Both engines and gears spun the same direction, and the bell shaped reduction units on the back of the gears had planetary gearsets for both reduction and to swap rotation. Apparently they could not get the gear tooth counts right for exact same ratios. Some ZF/Hurth boxes have the same issue. Can be annoying.

Not an issue if engines are counter rotating, but that creates annoyances of it's own.
Ski in NC is offline   Reply With Quote
Old 06-09-2016, 10:39 AM   #7
Guru
 
Aquabelle's Avatar
 
City: sydney
Country: australia
Vessel Name: Aquabelle
Vessel Model: Ocean Alexander Flushdeck
Join Date: Jun 2012
Posts: 538
Thanks as always Eric
__________________

Aquabelle is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 10:36 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012