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Recommendations for prop pitch control?


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Hi chap owners. I am getting really excited to get the boat in the water this weekend. As the new season is upon us, on the second year of owning my 246sii, I thought I would pose a question to all those who are savvy about speed and pitch control.

Last year (at the beginning of the season) during boat orientation the dealer recommended 1/4 in raise on my prop when I reach above 3,000 rpms. However when adjust to about halfway from 1/8 to 1/4 and get into the high 30s the boat will begin to porpoise or the bow will begin to bounce slowly.

I have been thinking of the following 3 options:

1. Do I just adjust the prop down until the boats stops porposing and accept the fact that my guage may be inaccurrate?

2. Do I just assume that when the porposing of the bow stops that it is at the proper pitch?

3. Assume and accept that the current pitch is okay for the particular speed based on the bouncing affect?

Thanks for all your input. Here is what I have: 2012 246SSI with Volvo 5.7 GXi 320 HP.

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Modern 2012 boats do not porpoise. None of the 50 or so that I know about.

Boats stored on a trailer with incorrect support places do develope porposing.

Stored in a dealer on boat stands can also have porposing if the bottom was not made strong enough everywhere.

Hopefully your trim indicator is just reading incorrectly. Warranty & dealer work.

Caution.......You can wear out the stern drive very quickly if the drive is trimmed up TOO HIGH for too long. The large angles will bang the daylights out of the joints

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Not sure what type of drive you have, but the Merc BIII outdrives tend to not need much in the way of a trim up to be correct. It is all a matter of getting use to the boat. Bring it up on plane with the trim all the way down and then bring the throttle back to around 3800 rpm. Then tap the up on the trim switch and watch what happens with speed and rpm. Keep taping the trim up until you see rpm go up and speed drop, then tap it down a couple of times. You can then play around in that area with a tap up or tap down till you find that sweet spot.

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A lot as was mentioned above depends on conditions, and what drive a person has on their boat. A single prop drive can be trimmed a lot higher than say a Bravo3 / DP drives, as the twin prop drives generally provide a lot more stern lift. If a trim gauge is accurate, 1/8-1/4 up trim is all a B3/DP drive likes to run at.

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A lot as was mentioned above depends on conditions, and what drive a person has on their boat. A single prop drive can be trimmed a lot higher than say a Bravo3 / DP drives, as the twin prop drives generally provide a lot more stern lift. If a trim gauge is accurate, 1/8-1/4 up trim is all a B3/DP drive likes to run at.

Like Shepherd says. On my boat they never like to go 1/4 up, most of the time they are in the 1/8 area.

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Thanks everyone, I no longer believe the dealer recommendation. I will do it based on feel.

That's what I do - we have the same boat, but with the Mercury package. I've got the analog gauge package and I trust my trim gauge to tell me I'm 100% up or 100% down and that's about it. My experience is exactly what Shepherd said - lots of trim range on the Alpha1, on the B3 not so much. I was very surprised about this, actually.

On the my 246, about two bumps on the trim button after settling out in the 3600 to 3800 rpm range is about all I can see any real response from. I will usually readjust trim if I drop down or speed up by 800-1000 rpm - I usually can tell the boat is responding to that, but it's mainly by feel and hearing the engine/prop response and watching the reaction of the tach and speedo (will see rpm and mph increase slightly as trim gets optimal for that setting). Can barely see the trim gauge move at all in this case.

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One side bonus of placing a Bravo 3 drive in the Bravo 1 position, and then recalibrating the trim is that you can have the needle move more. The 246 SSi WT models with MerCruiser Bravo 3 power that we've placed in the Bravo 1 position have given us faster planing, with no vibration, or ill handling while trimmed in all the way. For a model with the round analog gauges, the trim sender would have to be adjusted by hand.

Boats with an extended V-Plane design, such as Chaparral's and Cobalts, etc. typically have more stern lift than say a Sea Ray with a conventional V-hull, etc. A dual prop drive, such as a Bravo 3/ DP give more stern lift than their single prop brethern, and thus affects how a boat responds to trim.

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