Dialing in 27 Seacraft engine height, etc.
 

As most of you know, I have 27' Seacraft with new 48 inch wide body Armstrong bracket with 30 inches of setback and 14 degree transom angle. Engines are twin Honda 250s with 30 inch shafts. Boat jumps on plane and runs very flat at 51mph at 6300 rpms WOT with 15.25x17 three blade Solas props. Engines are mounted in hole number three of five. When using a straight edge coming off of hull (measured directly below motor) the cavitation plate is roughly 4 inches above hull. No trim tabs yet.

While speed is fun, rough water performance is what I care about the most - I boat in Maine and the water is always rough. When running in chop at cruise (27mph or so) at the current engine height, you can hear some prop ventilation. With the current set-up motors like to be trimmed all the way in (negative) and when I trim them out one click at higher speeds, the response is okay but not great. However, if I trim them out two or three clicks, boat will porpoise a bit.

In the interest of getting great rough water performance while maximizing fuel efficiency, I am thinking of lowering engines one hole and switching to four blade props because of their increased surface area. In doing so, I was hoping to minimize ventilation, lower planing speed and maybe give myself some more positive trim, so I can run engines perpendicular to water surface at higher speeds where fuel efficiency is greatest.

Obviously the boat is running pretty darn good and I am splitting hairs here but if you guys have any suggestions or if I am missing anything and/or may have interpreted things wrong, I am all ears.

Start with good 4 blade props before you do anything. If Merc props can be adapted to Honda I would look a Rev 4 or Bravo 1.

Do as Moose suggests first. I think this is the kit for the Honda engine to Mercury/Quicksilver prop (double check). I had a Vengeance prop from my old EFI Merc, I used this flo-torq to mate with my 250 ToHondasu. I ended up going to a different brand with larger diameter, larger surface area prop and I let my neighbor use it.......like forever, he sold the boat with it.

https://www.amazon.com/QuickSilver-8.../dp/B002IZDJH6

I’m curious what you have for a current minimum plane speed with the new setup. Looking forward to seeing how those moves contribute to that number. Really like how the Hondas look in white.

Long ago I had a conversation with Ken at PropGods about ventilation like that (different boat) - if my memory is correct, he said to get the prop generally right for a light load and then a little extra cup on the tips would fix that. Probably worth giving him a call.

I agree with Moose try the 4 blade props 1st ! I raised the height on my 300 etec on my 23 and had the same issue put on the 4 blade and haven’t noticed it since.
Mine was the same way wanting the motor tucked under as well

I could fry up some cement Hush Puppies?

The 4 bl props are just where you want to go.

In general, tip cupping brings bow lift.
Close to the hub, gives stern lift.

The Bravo is gaining in popularity.

These hulls love nothing more than stern lift.

Fred had Stoner build a new bracket in January had to wait for the muscle for his 27 ! Installed late last week ... Stand-by more later !

Attachment 23107

Those should work nicely!

Oh yea!

Time for a boat ride.... Hang-on !
Attachment 23152

Attachment 23153

How did I miss this? I tried sending a DM via Facebook to Freddie but says not available.

Ed, Fred absolutely hated FB, so he stopped using it...
I think I gave you his cell if not let me know and will get it to you..

I talk to him about three times a week.

Hi Ken,

I figured something was up. I don't have Freddie's phone or email. If you have them, please send my way.

Thanks

How did the boat ride go? Curious on the performance on this sweet rig.

I have about 14 hours on my second set of Honda 250s and maybe 2 of those hours are with the new 4 blade Powertech 15.25 x18. It has been crappy for 3 weeks here so I will get some good performance numbers in the coming weeks.

I spent about five hours on the boat today and had the chance to run it in varying conditions (fairly calm ocean, crazy ebbing river).

With the 15.25x18 Powertech 4 blades I am seeing 50-51mph (barely) at 6100rpms with engines one hole lower than last year's set. (Old props were Solas Lexor 15.5x17 3 blade with 50/51mph at 6300 rpms.

With the Powertechs my optimum cruise is 3200rpms burning 13.5 gph at 25mph with a efficiency range of 1.60 to 1.86mpg depending on tide/wind/current.

Best part is I now have a mid range, no ventilation and much more positive trim. With that said, I would like to try and run the 4 blades back up in the original hole but that may have to wait until next year as our season is so short. I took some video of the cavitation plates at cruise today but not sure if I can post it here?

So far it feels like a different boat, especially in that cruise range. With old props I was always jockeying the throttle to stay on plane. (It was the same story with my Mercs and the Mirage Plus props)