Motor Rotation - 390 Express (1996)

[390Express]

I was under the impression that both of my motors were standard rotation, and the counter rotation was done in the gear drive or the transmission, but after talking with a Trojan expert (whos expertise are self-admittedly only valid until the 1991-1992 vintage, when Trojan went out of business), I'm not so certain. I can say that both of my motors have the distributor wired to the same firing order, but that means nothing, as who knows if someone wired the distributor wrong, and I've never actually heard either motor run.

I have compression in the stbd motor, and it's more or less ready to go. I drained 100% of the gas out of the stbd tank (over 100 gallons!), tested for compression, changed the plugs, bought a new gas line, and I'm ready to add fuel and see what happens with this motor... The only issue that I can see having with the stbd motor is perhaps an electronic ignition/pcm issue, as the mechanics all seem good.

I am just starting the same process with the port motor. I already bought a new starter (for a std. rotation motor, perhaps mistakenly), had the alternator rebuilt, and drained and changed the oil. I'm ready to get the rest of the gas out, have a new gas line made, do a compression test and try firing the motor... however, I am now concerned that my port motor is actually a counter rotating motor, and I bought the wrong starter. Any good or simple way of telling?

[mjk1040]

I do believe the port is LH rotation and the Starboard is RH Rotation for your crusaders! Go check your props. they should be stamped LH on the Port prop and RH on the Starboard prop.

[buster53]

I do believe the port is LH rotation and the Starboard is RH Rotation for your crusaders! Go check your props. they should be stamped LH on the Port prop and RH on the Starboard prop.

The props will be counter rotating no matter what the engines are. The engines are either counter rotating from the factory or they are both standard rotating with the change over at the transmission.

That is the posters question...he's not sure if he has two standard rotating engines or two counter rotating engines

[waybomb]

Follow the wires on the cap to plug. If both are the same, then you have normal rotating engines.
Or, bump the engine and see what rotation each spin.
Also, the timing indicator at the damper would be opposite each other if counter rotating; one would advance clockwise, the other counterclockwise..

[Viper]

The last '96 Trojan express I worked on had 502 Crusaders and one of them was a counter-rotator. That's no guarantee yours is though. The way the plug wires are run is a giveaway but you don't know what the previous owner did before laying her up. If that's the way she was wired and she ran, then it's standard rotation. Don't install the new starter until you confirm the engine rotation first. You could take the old starter into a good re-builder that has experience with marine apps and they should be able to tell you if it's standard rotation or not. The casing might even be stamped LH or RH. How they're mounted on the engine makes a difference so you'll need to tell them that. Are there any markings on the engine; model number, serial umber, etc? Crusader should be able to help if you provide that. I believe within the serial or model number there should be an L or R indicating right or left hand rotation, the third or fourth letter rings a bell. There may also be a firing order cast into the intake manifold. This would indicate the rotation as well.

In a straight through shaft application, with the front of the engine facing the bow, the standard rotator (LH - left hand) is usually on the port side, and the counter rotator is on the starboard side. This is the normal configuration for pleasure craft. This rotates the props outward from the center. In some racing applications, this rotation is reversed. With v-drives, the counter rotating engine should be on the port side.

This is a good diagram illustrating starter rotation for the standard and counter-rotator engines depending on where the starter is mounted:
https://bpi.ebasicpower.com/faq/starterrotate.htm

[Viper]

Qr Bbpost .....the timing indicator at the damper would be opposite each other if counter rotating; one would advance clockwise, the other counterclockwise..

+1
forgot about that Fred. Good call.

[390Express]

Qr Bbpost Follow the wires on the cap to plug. If both are the same, then you have normal rotating engines.
Or, bump the engine and see what rotation each spin.
Also, the timing indicator at the damper would be opposite each other if counter rotating; one would advance clockwise, the other counterclockwise.

Thanks a ton WayBomb.

The motors had the same wiring on the distributor, but I didn't know if someone had fiddled around with it before I bought it. I bought it non-running, and the starter was bad, so I couldn't bump it to check the rotation. However, the timing markers are both on the right side of the dampener. At this point, I think it's fairly safe to say that they're both std. rotation motors.

Thanks for the help gang!

I have oil pressure, compression, new starters... now I just need to see why I don't have fuel pressure, and check for spark. Hopefully I'll have a running motor by the end of the week, and in the water next!

[waybomb]

The timing markers ARE on the same side of the engine. If counter rotating, one would should advance one way, and the other one the other way.
TDC for #1 is in the same place no matter which way the thing turns.

[390Express]

The timing markers ARE on the same side of the engine. If counter rotating, one would should advance one way, and the other one the other way.
TDC for #1 is in the same place no matter which way the thing turns.

Thanks Waybomb. So you’re saying that the markers will be in the same position, but read opposite? If I’m understanding correctly, if mine both start at 16 deg, and work down, as the motor turns clockwise, they’re both right hand rotation, correct?

Pics of both of my timing indicators below.

[waybomb]

Yes sir
Next time you are down there, mark the damper line and your specification advance with white paint.
Makes checking timing easy