Cruiser Performance, A Need For Slow??

[mrz333]

Hi! I'm new to this forum and to power in general (sailed). I recently purchased an '04 28' express cruiser with twin Volvo 4.3L & SX drives. It was sort of an experiment to see what I wanted in a power boat having had limited experience with them.

This boat is fast with a plane speed of about 24/25 kts @ 3400 rpm and a top speed of 50mph. I don't need the 50mph but do like to have that good fuel eco-cruise at 30mph this boat does have.

Even with trim tabs bow down I can't seem to get an on plane lower cruise speed or better performance at say 15 to 20 kts.

Here in SW FL there's lots of narrow channels to navigate to get to open water. Top speeds there is 30 MPH. No problem with that. But, most boats here seem to plane at lower speeds and, with the narrows, we form a queue. I can't follow them and stay on plane so I plop off then power up a lot just to stay out of trouble and keep my place in line. Can't use bigger tabs because the boat will become unstable at higher speeds and the drives are in all the way.

Is there a remedy like different props, adding tabs, hydrofoils for I/Os?
Thanks

 

[rbh]

Re: Cruiser Performance, A Need For Slow??

With our boat its legs fully trimed in, as much weight to the bow as possible, we don't have to use the trim tabs as it pops up on plane at about 10mph and holds, but I know that we are over propped and have a hard time hitting 40 mph at WOT which is 4100, should be 46-4800rpms.

 

[83Evinrude]

Re: Cruiser Performance, A Need For Slow??

I don't think you will find many here recommending a hydrofoil. Since you already have tabs probably your only other options are changing the props and loading the boat differently.

I would ask a moderator to move this to the prop forum. You should also post as much info as you can about the boats weight, gear ratios of the lower units, current props, and rpm/speed at WOT.

 

[45Auto]

Re: Cruiser Performance, A Need For Slow??

we don't have to use the trim tabs as it pops up on plane at about 10mph and holds,

Must be that colder water up in Canada or something! Ain't no 270 Sundancers down here (New Orleans) area that will plane ANYWHERE near 10 MPH.

Hull speed on a 270 is what, about 9 MPH? That means basically that the wave the boat is creating is the length of the boat. To plane the boat now has to "climb out of the hole" and climb up that wave it is creating. No way that's going to happen at 15 MPH, much less 10 MPH.

 

[rbh]

Re: Cruiser Performance, A Need For Slow??

Must be that colder water up in Canada or something! Ain't no 270 Sundancers down here (New Orleans) area that will plane ANYWHERE near 10 MPH.

On the speedo not the GPS, so I guess it should be 10mph++
But being as it's alittle overpropped, it sure gets up there quick.

 

[mrz333]

Re: Cruiser Performance, A Need For Slow??

To plane the boat now has to "climb out of the hole" and climb up that wave it is creating. No way that's going to happen at 15 MPH, much less 10 MPH.

What, then, would be a reasonable minimum planing speed to look for? Without the worry of high end performance, would a prop change out give me a plane at 20 mph? I guess I'll move this post to the prop forum but I would like to hear as much input a possible. Changing out 2 stainless props is not an inexpensive experiment!

 

[Alumarine]

Re: Cruiser Performance, A Need For Slow??

What, then, would be a reasonable minimum planing speed to look for? Without the worry of high end performance, would a prop change out give me a plane at 20 mph? I guess I'll move this post to the prop forum but I would like to hear as much input a possible. Changing out 2 stainless props is not an inexpensive experiment!

I might be wrong (and I often am) but I don't see how changing props will change minimum planing speed. Time to plane sure.

I would think that was hull/trim dependent.

 

[QC]

Re: Cruiser Performance, A Need For Slow??

Can't use bigger tabs because the boat will become unstable at higher speeds and the drives are in all the way.

'splain me 'dat please. Not feelin' it . . . I have extra large and long tabs and my gut tells me I am more stable at higher speeds because of it. Our boats are very different, but that still don't compute for me.

Edit: Oh, and if you put hydrofoils on that thing, I will get my scuba license, fly over there, and take them off while you ain't looking. Watch for the bubbles . . .

 

[mrz333]

Re: Cruiser Performance, A Need For Slow??

'splain me 'dat please. Not feelin' it . . . I have extra large and long tabs and my gut tells me I am more stable at higher speeds because of it. Our boats are very different, but that still don't compute for me.

The boat is a Regal 2765 with regal designed fastrack hull. LOA 31' with swim, beam is 8'6" & weighs about 7500 lbs. Tabs are 9" x 18" and take the entire transom area available for tabs. Hull design traps air under the stern 1/3 and lifts it at speed. The trim tab adjustments are very sensitive at higher speeds. The controler is not the Bennet automatic and the drive-in angle helps by adding additional lift with their 'nose down' normal position.

I was told, maybe wrongly, that increasing the tabs to a custom size like 12 x 18 or 15 x 18 would lift the stern sooner but would invite overcontrol at higher speeds. There is no tab position indicator and if I don't raise the tabs or evenly set them before planing I lose a lot of helm control once I'm up on it.

I'm not sure what the props are set at but they are the size & pitch for best performance at 50mph.

With all this info I'm not sure what to do. I asked Regal but they don't want the blame if I end up wrapped around some ATON.

Having limited experience I don't know how much of the problem is based in poor seamanship on my part.

 

[QC]

Re: Cruiser Performance, A Need For Slow??

Well . . . my first reaction is that they will only be a problem at speed if the operator leaves them too far down. Pretty obvious when you do that . . .

Like others I am surprised she won't plane at a lower speed. I need to dig up some notes on bigger boats I have run, but I can plane my boat at 12 MPH with full tab and she is very easy to control there and up to 20 MPH with full tabs. I don't run like that very often, but when I find a reason I like it a lot.

 

[jaxnjil]

Re: Cruiser Performance, A Need For Slow??

What, then, would be a reasonable minimum planing speed to look for? Without the worry of high end performance, would a prop change out give me a plane at 20 mph? I guess I'll move this post to the prop forum but I would like to hear as much input a possible. Changing out 2 stainless props is not an inexpensive experiment!

go to the i boats prop section and look for a pair of 4 blade aluminum props. dropping down a couple of pitches will help your problem.

this would be the cheapest way to find where you want to be on prop pitch.
you will lose some top end speed. your pushing a lot of boat there and trying to cruise at your almost on plane speed. not easy as you now know.
the 4 blade will give you a little more traction. hope that makes sense