ultprthead wrote:
My tabs are set in the bow down position as bow up has never been necessary.
Great answer Gordon !!
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| Volvo Duo-Prop and Trim https://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=4041 |
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| Author: | ultprthead [ Mon Jul 13, 2009 10:06 pm ] |
| Post subject: | Volvo Duo-Prop and Trim |
Dumb question. I have a SL262 with the Volvo 8.1 Duo-Prop and trim tabs. My old boat had a Merc Alpha 1 drive that once I got up on plane, I would trim my drives up about 1/4 of the way...and ride on top of the water, rather than plow through it. When I trim up my new boat, two things happen...I don't seem to come out of the water, and my prop tends to want to cavitate (more noticable around turns (wide turns). My tabs are set in the bow down position as bow up has never been necessary. I guess my question is do I still need to trim up a duo prop in the same way that one would a single prop set up... Any help would be appreciated. Thanks! |
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| Author: | M3eater [ Mon Jul 13, 2009 11:21 pm ] |
| Post subject: | Re: Volvo Duo-Prop and Trim |
no With that said, The heavier boat will not allow you to trim up as much as you used to with the other boat. Additionally, you should not have the trim tabs down when just running along, after planing, unless you are trying to stay on plane at a lower than normal speed. Having the tabs down (bow down) and trimming the drive up (bow up) will be fighting each other. When you are cruising along, you should normally have the tabs up (bow up) and then little by little trim the drive up until you either hear the cavitation or you see that the speed is no longer increasing. Just bump the trim button for an instant at a time, then give it a few seconds to settle in before giving it another bump. You WANT the bow of the boat to lift out of the water, for less drag, more speed, better fuel economy and better control at speed. Of course, this is assuming you are not in very wavy conditions or trying to plane at a low speed. With the tabs down (bow down) you are forcing the bow into the water rather than allowing it to lift up and ride on the rear sections of the hull. |
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| Author: | Graham R [ Tue Jul 14, 2009 3:58 am ] |
| Post subject: | Re: Volvo Duo-Prop and Trim |
Gordon, Very well explained about the tabs; also about the boat weight affecting the degree of useful outdrive trim that can be used. I previously had a 225 Sundowner with a 5.7GSI/ DP (280 hp). I currently have a 245 Sundowner with a 5.7 GXi/ DP (320 hp). The outdrive trim had a much bigger influence on the speed of the smaller boat; I hardly have to trim the drive out at all on the heavier 245 to reach maximum speed; all it seems to do is make it noisier as the end of the stub exhaust hose gets exposed. Graham |
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| Author: | Flying Sushi [ Tue Jul 14, 2009 6:07 am ] |
| Post subject: | Re: Volvo Duo-Prop and Trim |
Welcome aboard…. We only have a very small range of trim in our size of boat with DPs. You should have F6 props on your boat but some use F5 props as well Put trim down and once the boat come out and start plane, trim up a little and off you go. You can feel the drive become smoother….. Try not to go by the trim gauge and go with how the boat feels. I use trim tabs a lot based on the water surface condition but never down when I take off…… Enjoy your summer! Oh by the way we want picture! |
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| Author: | Cap'n Morgan [ Tue Jul 14, 2009 7:11 am ] |
| Post subject: | Re: Volvo Duo-Prop and Trim |
ultprthead wrote: My tabs are set in the bow down position as bow up has never been necessary. Great answer Gordon !! |
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| Author: | ultprthead [ Tue Jul 14, 2009 1:48 pm ] |
| Post subject: | Re: Volvo Duo-Prop and Trim |
Thanks for all of the great information. I will try it next time out and let you know how it works out. Thanks again! |
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| Author: | DaleG [ Tue Jul 14, 2009 2:43 pm ] |
| Post subject: | Re: Volvo Duo-Prop and Trim |
I think all the basic info has been pretty correct. I might add also that Four Winns boats with the extended sponsons (extended planing surfaces beyond the basic transom) do not allow a lot of bow up trim which frees up the hull and increases speed as you mentioned in the original post. I am not sure the new hull you have still falls into that category. The extended planing surfaces do get the boat onto plane quicker -- which is their purpose, but they also restrict the bow up attitude which helps reduce wetted surface area and increases speed. |
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