Engine Rotations

Cecil Phillips

New Member
Sep 7, 2019
6
Jacksonville, FL
Boat Info
1993 Sea Ray 300 Weekender, German GPS, Depth Sounder
Engines
2) 5.7 Mercruiser inboards
I just picked up a 1993 Weekender 300 it has two inboard 5.7. Can anyone tell me if they are both standard rotation or a right and left?
The engines have been changed and there are no serial numbers. The port engine was just changed and the starter turns it counter-clockwise (looking at the front). Starboard starter needs to be replaced.
 
By 1993 they were standard rotation for both motors. The counter rotation is taken care of in the transmission. Although they are replacements and you can’t identify them, there is a good chance they’re both standard rotation because of the transmission.
 
Look at the props - if both props have the blades angled the same way, the engines are both standard.
 
Look at the props - if both props have the blades angled the same way, the engines are both standard.

?
With standard rotation inboards and one transmission counter rotation, the props would be different. Left hand and right hand. No?
 
If a motor is turning CCW when looking at the front of it, it`s a reverse rotation motor

Sounds like he is looking to get the right replacement starter for his starboard motor.
 
Sounds like he is looking to get the right replacement starter for his starboard motor.


I haven't seen a reverse rotation engine in decades. The OP said the port engine was just changed and the starter rotates it the left (CCW) which would make it a reverse rotation engine. I don't buy it. The OP needs to look at the harmonic balancer and see which way it turns when the engine is cranked.

I also believe that when reverse rotation engines were popular....they went on the Starboard side....not the Port. This was done to load the torque towards the starboard hull.
 
?
With standard rotation inboards and one transmission counter rotation, the props would be different. Left hand and right hand. No?
Good point - I was reading too quickly and had outdrives on my mind. (Although there are CC drives, too!)

Cecil, just to double check... you looked for a serial number tag on the flywheel housing, just above the starter?
 
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If the port engine is a confirmed reverse rotation, leaves little doubt what the stbd is.

From reading his post, I think he confirmed that the port is standard rotation.
His starboard needs a starter. I’m assuming he is trying to determine what starter he needs. Hopefully he’ll check back soon.
My money is on both being standard rotation in a 1993 Sea Ray.
If the old one isn’t totally frozen, and since he has to remove it anyway, he can just check which way the starter spins on the ground with a jump pack or if he doesn’t have a jump pack he could just use cables connected to his car battery.
 
If the crank is turning CCW looking at it from the front of the engine it's a reverse roto.
Now if he's calling the rear of the engine the front...well.
 
Hey Guys
Thanks for all the input! I compared the rotation of the port engine (using the starter) with my truck and it definitely rotates opposite from my truck. The port engine was just replaced (is not running) I believe it was a counter rotating engine because the original starter was put on the new engine. I tried the port engine starter on the starboard engine and it wouldn't run. I got another starter and put it in the starboard engine and it fired up. Put it in forward and the prop turned in the right direction. The port starter has CW on it and keep in mind this is an inboard so the starter mounts on the bell housing and not the block. I am calling the front of the engine the end with the harmonic balancer and pulleys and belts, even though it is facing aft.
 
Hey Guys
Thanks for all the input! I compared the rotation of the port engine (using the starter) with my truck and it definitely rotates opposite from my truck. The port engine was just replaced (is not running) I believe it was a counter rotating engine because the original starter was put on the new engine. I tried the port engine starter on the starboard engine and it wouldn't run. I got another starter and put it in the starboard engine and it fired up. Put it in forward and the prop turned in the right direction. The port starter has CW on it and keep in mind this is an inboard so the starter mounts on the bell housing and not the block. I am calling the front of the engine the end with the harmonic balancer and pulleys and belts, even though it is facing aft.


That makes more sense now. Since the engines face aft....the torque goes to the outside of the hull. Having a CCW rotation engine on the port side would accomplish this. A normal rotation on the Starboard aft facing engine would push the torque to the starboard hull.

I am surprised that your 1993 came with a CCW engine but Sea Ray is always full of surprises. Glad you got it sorted out.
 
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Me too, but now the new port engine is the wrong engine. As my old friend Rosanna Rosanna Danna use to always say "It's always something"
 
5.7 inboards, direct drive or V drive, With direct drive the front of the motor faces the bow. With V drives the front of the motor faces aft
What you have describes a V drive setup Looking at the balancer on the motor , if it turns clockwise its a reverse rotation motor using a standard rotation starter if it turns counter clockwise its a standard motor using a reverse rotation starter
Check the firing order std rotation from #1 plug wire is 1,8,4,3,6,5,7,2 clockwise, reverse rotation is from number 1 1,2,7,5,6,3,4,8
A aft entry starter for a bell application for a std motor is a reverse rotation starter, a starter for a reverse rotation motor is a standard rotation starter
 
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another indicator is the direction of the dist rotor All GM dist turn in a clockwise direction no mater what engine rotation. Remove the dist cap and turn the motor , does the dist turn CW or CCW
 
another indicator is the direction of the dist rotor All GM dist turn in a clockwise direction no mater what engine rotation. Remove the dist cap and turn the motor , does the dist turn CW or CCW
Does that mean the oil pump is reverse rotation to? Thought it was just the wire configuration that was different.
Edit.. Misread your post. See what your doing there now.
 
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If this thread proves one thing ......I’m so glad all the manufacturers figured out how to build a trans that worked for both sides with standard rotation engines. :)
 

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