Engine Rotation

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blair
Registered user
Posts: 73
Joined: Tue Sep 04, 2012 11:29 pm

Engine Rotation

Post by blair »

So I'm installing new impeller assemblies today and realize I don't know which engine turns in which direction.
While poking around the engine bay, I noticed that the elvet drives have a direction arrow on them. Is it safe to assume that BOTH engines turn left (as per standard) and the reversing takes place at the transmission? My parts guy says this may be so, but I want a second opinion. I installed the impellers as if this is the case. \do \i have to go back and reverse the input/output hoses?
Thanks,
Blair
1979 Trojan Tricabin with twin 255 Mercs
11' Inflatable dingy with 4 Hp merc
On the Trent canal system at Young's Point , Clear Lake, Ontario
Jerry
Moderate User
Posts: 309
Joined: Fri Dec 05, 2008 11:30 am
Location: Presque Isle Bay, Erie, Pa.

Re: Engine Rotation

Post by Jerry »

Contrary to popular belief, In my experience I have found that the impeller will flip itself to the proper orientation as soon as you start the engine.
Image
blair
Registered user
Posts: 73
Joined: Tue Sep 04, 2012 11:29 pm

Re: Engine Rotation

Post by blair »

Hi Jerry,Thanks.
The impeller certaily WILL flip in rotation.I stood in the engine bay for about 30 minutes turning it one way and the other,watching for which side the cams were compressed and then released.as this is supposed to indicate the intake side.An old sparkplug.inverted into the keyway worked great for rotating the impeller.
My concern was trying to make sure I put the input and output hoses in the correct positions,which seem to be dependent on engine rotation.I would think it wasn't too important,as it just looks like the same configuration,just reversed.Water SHOULD flow regardless of rotation.Either way,I'm taking my batteries up today and will remove the coil wires,give her a bump and see the direction of rotation.
Thanks,
Blair
1979 Trojan Tricabin with twin 255 Mercs
11' Inflatable dingy with 4 Hp merc
On the Trent canal system at Young's Point , Clear Lake, Ontario
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srokag44
Sporadic User
Posts: 98
Joined: Wed May 09, 2012 1:16 pm
Location: Merritt Island, FL

Re: Engine Rotation

Post by srokag44 »

Reverse engines normally are stamped with R.H. (right hand) on the nameplate. If the engine firing order is labeled somewhere that can also tell you the rotation.

Which hose is connected to which side of the pump does make a difference.

Image

For this image rotation is CCW and the inlet is the top left and exit is the top right.


This will provide more detail: http://www.jmpusamarine.com/?page_id=337
1985 Trojan 10 Meter International Sedan
blair
Registered user
Posts: 73
Joined: Tue Sep 04, 2012 11:29 pm

Re: Engine Rotation

Post by blair »

Thanks for the image. It helps to see how the cavity makes all the difference. I was able to set the starboard engine properly, as the P.O. replaced that side with the single body raw water assembly. Seems he left the two piece body on the port engine, so I'll confirm the input/output as per the diagram.
Much appreciated!
Blair
1979 Trojan Tricabin with twin 255 Mercs
11' Inflatable dingy with 4 Hp merc
On the Trent canal system at Young's Point , Clear Lake, Ontario
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