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Re: Motor Rotation - 390 Express (1996)

Posted: June 1st, 2018, 8:38 pm
by km1125
Since I just happened to be on the boat, and have two Crusaders sitting underneath me, I decided to snap a pic. One of those is worth 1000 words, right? (btw, I could only see your second pic.. the first one only loads partway)

I have opposite rotation engines. These are 1983 carb motors, but the timing marks should be the same, if not similar.

If you look for the "before" numbers on the indicator, the crank rotates from those numbers to the TDC mark.

Re: Motor Rotation - 390 Express (1996)

Posted: June 2nd, 2018, 12:59 pm
by 390Express
km1125 wrote:Source of the post Since I just happened to be on the boat, and have two Crusaders sitting underneath me, I decided to snap a pic. One of those is worth 1000 words, right? (btw, I could only see your second pic.. the first one only loads partway)

I have opposite rotation engines. These are 1983 carb motors, but the timing marks should be the same, if not similar.

If you look for the "before" numbers on the indicator, the crank rotates from those numbers to the TDC mark.


Thanks KM, both of my motors have timing markers similar to your port, std. rotation motor. What a relief. I was concerned that I was going to have to pull off the brand new starter that I just put on, and wait another 4-5 days for a new one.

I'm surprised that your starboard motor is your counter-rotating motor. My Baja had a LH rotation on the port side, I guess it's just another difference in the cruiser vs offshore world, but I've always been taught that rotating "in" (with both props spinning toward the middle of the boat) would add drag and bring the aft lower in the water. Seems like the opposite of what you'd want to do in a cruiser?

Re: Motor Rotation - 390 Express (1996)

Posted: June 2nd, 2018, 4:46 pm
by Viper
It depends on the hull design but in some racing applications, prop rotation is reversed so the tops of the props turn into each other to provide stern lift and get the transom out of the water. In recreational applications, standard prop rotation is RH. In a twin application, the RH prop is on the starboard side so that the tops of the props trun away from each other.