Rigging Counter Rotation Outboards

[RetNav]

As has been posted before, I have a 256 Dusky, 1990 model WAC with twin 200 hp evinrudes. Both motors are 1990 models.

Does it matter what side the counter rotating motor is mounted? I have searched the site and Dhadley stated "it depends on what type hull and what you want to accomplish" (not an exact quote).

Currently the C/R motor is on the port side and it has never pulled its load. It won't hit close to the same rpm's as the stbd motor. About 900 rpms less than the other motor. The dealer will only check the compression and then declare its in good condition, nothing wrong with it. It seems he can't hook it up to his dyno as it rotates the wrong way. So I'm thinking I will swap the lower units and then get him to hook it up and check it out.

I know there is something wrong from running it for the past two seasons. Its performance is less than the other motor in all categories.

How about some thoughts on this subject please.

 

[Dhadley]

Re: Rigging Counter Rotation Outboards

Not unusual at all. First we have to have the props measured to make sure they're the same, regardless of what's stamped on them. Send both to get measured.

Then look at set up. Look under the hull. Look at what's directly in front of the starboard motor and then the port motor. 99.9% of twin motors are rigged xx" from center and we find out the lifting strakes are not equal distance from the center of the keel.

Run a straightedge from the AV plate to the hull when the plate is parallel. Make sure both are the same.

Measure toe-in. It should be 1/8" to 3/8" on a V bottom.

If all that checks OK, switch the lowers. If the motors are on a bracket, and we suspect they are on a Dusky, you'll probably get a little bit better efficiency with the counter on the starboard side.

Your dealer experience is not unusual. Even if he would hook it to the dyno all that tells him is the motor is good or not. With good compression we can be 80% sure it is OK anyway. To find out what's really wrong he'd have to actually get in the boat when it's in the water. Most dealers won't do that.

Let's start with the basics (establish the baseline) above and go from there.

 

[RetNav]

Re: Rigging Counter Rotation Outboards

Appreciate the information and will check it all out first.