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Thread: Uneven Counter Rotating Prop RPM

  1. #1

    Default Uneven Counter Rotating Prop RPM

    I have counter-rotating twin 200 Yamaha's, and decided to go to 4-blade stainless props, versus the stock aluminum 3-blade 19's that came with them. I first went to Solas 19 pitch 4 blades, and would get max 5500 rpm on the left, and 5000 on the right. That RPM split startled me a bit (I am new to bigger boat boating). Since I just had the post break in service prior to this run, I put the stock 19's back on, and it ran as usual - 6000/6000. So the split difference wasn't the engines.

    I then went to 14X17 pitch 4-blades and got about a 300rpm split, but more suitable rpm's. Max rpm 6100/5800. That's with max nose up trim. I didn't get as many numbers with the 17's. Rougher seas, and busier. But overall, better gas mileage, and it appeared a few knots speed loss. Maybe a few more than a few. But with the 17 run, there were 5 people on board, vs just one or two with the 19's.

    What disturbs me is the rpm split. I have heard that with counter-rotating props, and four blade stainless, this is not unusual. Has anyone had similar experiences? I was told to swap out the 6100 (left) prop. If that didn't bring them closer, to get them blue printed, then adjusted by the prop shop (A1) to get them matched.

    Is this RPM difference unusual? If my stock 19's weren't so even, I don't think I would worry about it so much, but find it irritating to always having to sync up the RPM's. Thanks.

  2. #2
    Member patrickL's Avatar
    Join Date
    Apr 2006
    Anchorage, AK


    I'm far from an expert here but do you know if you were hitting the rev limiter on your original setup? Mine hit it around 6000 rpm but I have 150s. I think the 200s are the same but not for certain. If you were hitting the rev limiter on your original setup then you wouldn't know if the engines were split from the beginning. Just something to think about. It may not have anything to do with the props but the engines.

  3. #3


    That's an excellent point. I don't know. I am in the process of running some more numbers in the 17's, and if the 300 split persists, I will have the higher one cupped to drop 300rpm. That seems to be the best solution for now. I like the props and what they do. The prop guy said he could cup it for 300rpm. That's beyond me, but that will be the plan if the next set of numbers are the same. Thanks for the reply.


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