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04-28-2018, 12:16 PM
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#1
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Veteran Member
City: San Diego
Vessel Name: Hiatus
Vessel Model: Cooper Prowler
Join Date: Jun 2017
Posts: 66
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Engine rotation
Does anyone know whether my starboard engine is counter rotating? I doesn’t run and I can’t find a number that confirms it.
1990 Cooper Prowler 10 meter
7.4L twin Mercruisers.
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04-28-2018, 12:39 PM
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#2
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Guru
City: Beaverton, Ontario
Vessel Name: Looking Glass
Vessel Model: Carver 370 Voyager
Join Date: Nov 2012
Posts: 1,240
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I would think that if your engines are counter rotating your props would be pitched opposite. Can you check them?
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Allan
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04-28-2018, 02:03 PM
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#3
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Guru
City: Seattle
Vessel Name: AZZURRA
Vessel Model: Ocean Alexander 54
Join Date: Aug 2017
Posts: 4,309
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Look at your transmission. Push both helm levers to the forward position. Now go look at the gear selector on each transmission. If they are both in the same position you have a counter rotating engine. I believe counter rotating engine is always on port side.
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04-28-2018, 02:54 PM
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#4
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Senior Member
City: Toronto
Vessel Name: Adios Dinero
Vessel Model: Bayliner 3988 2 x 330 Cummins
Join Date: Sep 2016
Posts: 336
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Bump the starter over while a friend watches the rotation on each engine.
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04-28-2018, 03:02 PM
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#5
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Senior Member
City: Lake Ontario
Vessel Model: Trawler Shopping 35-40'
Join Date: Mar 2018
Posts: 107
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Maybe crack open the raw water pump and take a peek at the direction of the rubber vanes?
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04-28-2018, 04:30 PM
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#6
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Senior Member
City: Toronto
Join Date: Nov 2015
Posts: 271
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Quote:
Originally Posted by CooperBrewer
Does anyone know whether my starboard engine is counter rotating? I doesn’t run and I can’t find a number that confirms it.
1990 Cooper Prowler 10 meter
7.4L twin Mercruisers.
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Interesting question .... I would think that all engines rotate only in one direction and the rotation is changed by the gearbox ... no ?
My twin Cummins rotate the same way ............. fb
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04-28-2018, 05:02 PM
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#7
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Guru
City: Seattle
Vessel Name: AZZURRA
Vessel Model: Ocean Alexander 54
Join Date: Aug 2017
Posts: 4,309
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Most diesels rotate only one way and counter rotation is done through the gearbox. With gas engines you could actually make the engine run counter rotation by changing the distributor, cams and starter motor.
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04-28-2018, 05:26 PM
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#8
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Guru
City: Duvall, Wa. USA
Vessel Name: Beach Music II
Vessel Model: 2003 Mainship 430 Trawler
Join Date: Aug 2014
Posts: 1,040
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Several years ago a friend with twin gas engines needed a new starter motor. He was a cheapskate and bought a rebuilt unit from the local auto parts store. When he tried to start the engine it sucked water into the cylinders. Guess what? It was a reverse rotation engine.
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04-28-2018, 05:33 PM
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#9
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Guru
City: Adelaide
Vessel Name: Kokanee
Vessel Model: Cuddles 30 Pilot House Motor Sailer
Join Date: Jul 2012
Posts: 3,218
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All modern engines (gas or diesel) turn counter clockwise (viewed from the flywheel) with just a few exceptions.
A few older engines such as the early Volvo MD series diesels turned CW. Some early Detroit's could be set up with the output on either end.
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04-29-2018, 05:43 AM
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#10
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Guru
Join Date: Oct 2007
Posts: 22,553
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Detroit 2 strokes can run in either direction as well a chose the side for servicing.
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04-29-2018, 06:23 AM
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#11
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Guru
City: Kilmarnock VA
Vessel Name: Wandering Star
Vessel Model: PSN40
Join Date: Apr 2016
Posts: 1,396
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If you have the Mercruisers that are in your signature, you could tell if the engine is CR by the firing order. Look for it stamped on the intake manifold or just trace the spark plug wires to see if they are in different positions on the distributor.
__________________
-Shawn-
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04-29-2018, 08:32 AM
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#12
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Guru
City: Cape May, NJ
Vessel Name: Irish Lady
Vessel Model: Monk 36
Join Date: Dec 2007
Posts: 4,966
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They could be either rotation. Usually marked with an arrow at the bell housing or crank pulley.
Did it used to run in its current configuration? If yes then crank it a second and you will know.
__________________
Archie
Irish Lady
1984 Monk 36 Hull #46
Currently in Cape May, NJ
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04-29-2018, 09:34 AM
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#13
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Guru
City: gulf coast
Join Date: Jun 2014
Posts: 3,440
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18436572 is normal rotation 12756348 is counter rotation
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04-29-2018, 12:14 PM
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#14
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Guru
City: Between Oregon and Alaska
Vessel Name: Charlie Harper
Vessel Model: Wheeler Shipyard 83'
Join Date: Jun 2016
Posts: 3,023
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The coming of hydraulic transmissions ended the need for counter rotating engines. The prop rotation is controlled in the transmission by diverting the oil flow.
Because it simplifies manufacturing and cuts the number of engine parts, there is no incentive to produce counter rotating engines. For operators that carry major spares, it cuts the inventory in half.
My Detroit Diesels turn in opposite directions. They use mechanical transmissions. One engine requires a different crank and cam. In other parts, different starter and water pumps on some models. But they use the same head, pistons, sleeves, etc.
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04-29-2018, 06:19 PM
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#15
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Guru
City: Wilmington, NC
Vessel Name: DreamQuest
Vessel Model: Prairie 36
Join Date: Jan 2016
Posts: 550
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One easy way to tell if your engines were set up properly to counter rotate is to look at the alternator fins on the belt pulley. If they are opposite, the engines are set up to counter rotate.
You don’t have to open anything up or turn anything on.
My Perkins 6.354 twins are counter rotating and the alternator cooling fins are facing in opposite directions.
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05-01-2018, 10:22 PM
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#16
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Guru
City: Gibsons, B.C., Canada
Vessel Name: Island Pride
Vessel Model: Palmer 32'
Join Date: Oct 2007
Posts: 4,414
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Quote:
Originally Posted by Ex Sailor
Interesting question .... I would think that all engines rotate only in one direction and the rotation is changed by the gearbox ... no ?
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That is not the case. Many diesels were counter rotating. Many of those engines, the counter rotating ones, are still around, in twin engine boats.
Although I have a single diesel, older engine, my engine model has standard and counter rotating models depending upon whether the boat was a single or a twin.
That has changed in most cases so now the newer engines all turn the same way with the shaft rotation change done by the gearbox.
The same goes for many gasoline engines. My previous boat had both types, standard and counter rotation.
The suggestion to try to crank the engines will tell you if you have a counter rotating engine. Just a bump will be all it takes. If one turns one way and the other turn the other way you have a counter rotating engine.
While looking at the FRONT of the engine where all the pulley/belts are:
-- if the engine rotates clockwise the engine is standard or L.H. rotation.
--if the engine rotates counter clockwise then it is counter or R.H. rotation.
THe determination is actually done at the flywheel but since most of us cannot see the flywheel this is acceptable just keep in mind which way those pulleys turn on which engine.
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05-02-2018, 05:40 AM
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#17
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Moderator Emeritus
City: Chicago, IL
Vessel Name: Bay Pelican
Vessel Model: Krogen 42
Join Date: Oct 2007
Posts: 2,993
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I am surprised by the question. What it tells me is the obvious that different boats are different or at least their operators are. When I do my engine room checks underway I can see the shaft rotating so I was surprised that this would not be the case with others.
__________________
Marty
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05-02-2018, 07:33 AM
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#18
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Guru
City: gulf coast
Join Date: Jun 2014
Posts: 3,440
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Shafts may turn in different directions than engines. They always turn in different directions from each other. That is achieved by changing engine rotation or in the transmission. So what you see on the shafts may not help determine engine rotation.
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05-02-2018, 07:44 AM
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#19
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Guru
City: Anacortes
Join Date: Nov 2012
Posts: 1,189
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Some clever methods I had not thought of here!
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08-21-2021, 10:15 AM
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#20
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Veteran Member
City: San Diego
Vessel Name: Hiatus
Vessel Model: Cooper Prowler
Join Date: Jun 2017
Posts: 66
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Engine rotation
Quote:
Originally Posted by ghost
Some clever methods I had not thought of here!
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Both of my big block V8 Mercruisers , fire in the same direction. They're virtually the same engines. The counter rotation of one prop, is handled by the hydraulic transmission.
This post was from long ago. Since this time, and with some help from this forum... my learning curve is almost a straight vertical line now. I have learned quite a bit, about my boat, and boats in general.
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