[cjay]

I have a 1986 36 open. It has new(er) caterpillar diesels. When I am cursing at 1800 RPM with no trim tabs at all the boat runs at 23 K. If I lower the bow, the speed picks up and I get an extra Knot. In my past boating experience, when I lowered the bow using Tabs, my speed decreased. What is it about this hull that makes my speed increase with the bow down?

[Uhehner]

The trim is a function of the weight aboard and where it's located. With full tanks aft you will need some trim. It's not putting the bow down as much as raising the stern. As the fuel burns off you will need less trim. My 36 Convertible runs best with no trim but then I never fill the tanks past 1/2. Why carry it out and then carry it home?
Capt. George

[jeffnt]

Also depends on sea state and tide,I always adjust my tabs with gps and floscans to find sweet spot and they are in different positions if running in bay or in ocean.I find that gph will be less if adjusted right too.I have a 1994 31 open hope this helps.

[jaywilliam]

Did you install the floscans or did they come on the boat? If installed then what make, model and how much work? Thanks!

[ingram622]

I agree!! "It's not putting the bow down as much as raising the stern." I had a 341 Meridian that was underpowered and I had to have the trim tabs down all the way just to get the boat to plain! On a boat this size it is more of getting the stern out of the water and if you play around with tabs while looking at the GPS speed you will see a big difference without touching the throttle. You can gain 2-5 MPH depending no the boat.

[T-FIN]

I have 2002 38 Open....not a huge drop in speed with tabs full down.... And ride generally softer...almost never retract tabs fully(except docking).... Use gps to find sweet spot.... Generally 2200/2250 rpm....top speed 30 knots at 2650...

[Chris Burkard]

Trim can absolutely affect speed and comfort.

Inboard planeing hull designs usually run best between 5 and 7 degrees. The easiest way to figure the sweet spot for your vessel (which will change with load, wind and wave conditions) is to run the vessel up to a comfortable speed, then trim for comfort. Then back off the tabs and see if your speed increases or decreases. If it increases, back off a bit more until it begins to decrease and then add a touch of tab. If it decreases, keep adding tab in small increments until your speed decreases and then back off just a bit and you are now at the most efficent trim for your current load, speed and sea conditions. Every time you change directions or if the wind and sea conditions change, you will have to retrim the vessel.