Most Efficient Cruise Speed For 260 Sundeck?

[Lidokey]

I have a 2012 260 Sundeck with the base engine. Over the 60 hours of operation I've had it, looks to me that I get my best fuel economy at around 3300 RPM which in relatively calm seas, moderate wind, gives me a speed of 21MPH (GPS readout) and the dash readout shows a fuel burn of 7 GPH which works out to 3 MPG. What I haven't yet done, but will soon is experiment with, is the trim. I cruise at that speed with the trim full down. (not referring to the hydraulic trim tabs) but the i/o unit trim.
My question is if I trim up a bit, that should lift the bow out of the water which ought to mean less friction and higher speed with the same fuel burn, right? Any suggestions on how I might find the optimal speed? Or will I find that I've pretty much found the sweet spot and any trim adjustment isn't going to be very noticeable.
Thanks in advance for any shortcut to determining this you can provide.

 

[Southpaw II]

You've pretty much got it right, but, at some point it takes more energy to lift the boat (reducing friction) than you get a return from in the form of speed. The result, if you lift the boat too much, is a loss of speed. I would start with whatever your minimum planning rpm is, and then increase it about 200 rpm. Then, lift the drive a bit to see if your GPS speed increases. If it does, lower the RPM back down to see if GPS speed decreases. If you think about it, it all boils down to RMPs/MPH. The lowest ratio is the most efficient.

Don

 

[SeaNile]

I never cruise with the trim all the way down. Too much drag. Go and play with the throttle and trim and you will eventually feel the sweet spot. Don't learn at 4500rpm but more like 3400-4000rpm. When you trim down you'll feel the boat slow down, the wake get "deep" and the water coming off the hull sides will be about where you are standing when driving, maybe even slightly forward of you. Trim up and you'll feel the boat come alive and honestly just feel better. If you trim all the way up the bow will bounce up and down and the prop wash will be way too flat and look like it's got too much air mixed with the water. Trim down slightly and that will be the trim to get the max speed. Not the most MPG necessarily but the fastest.

Even with 6-8 people on board I keep the trim down till about 3300rpm and then tap it up a few times and the bow will rise and the boat will feel much better. You can watch the MPH increase too.

I generally cruise about 3400rpm and trim about half way up.

Hope this helps but the best thing to do is go out and just play with the trim, slowly, at a modest speed.

 

[Lidokey]

SeaNile/SouthpawII
Thanks for the advice. I know its not a big deal, but every 5-10% of efficiency helps. Appreciate you guys sharing your knowledge.

 

[chuck1]

Just my 2 cent worth always found best was somewhere around 3300 for me.