Posted by gypsmjim on 08/24/17 - 6:54 PM
#23
EJO wrote:
gypsmjim
I did go ahead and bought a Doel Fin set.
The instructions are very vague as they don't tell you where to mount them on your anti cavitation plate.
As an engineer I wanted to know where to put these fins on the plate as the plate on the 60HP EPI 4 stroke is a lot longer than the Doel fins. No where in their mounting instruction do they give this info so I called customer service and was told to center the foils over the C/L of the prop equal to where the foil straight edge angles back to the cav.plate.
That said I did so and ended up with longer out of the hole shot with higher bow rise (engine tucked in all the way) same top WOT speed except much more prone to porpoising.
This was with 4 adults (800+lbs crew and all) the standard 3 bladed Vengeance SS prop. Yes I could plane at slightly lower speed but with two adult women on the bow cushion I felt like the bow was riding to high.
I will remove the $28 "fix" as it didn't really make it "perfect" and I didn't like the way the boat was riding or porpoising.
Pardon my tardy reply, but we have been on vacation again. Put a lot of gas thru the new Montauk these past few weeks. Our other boats are feeling neglected.....LOL.
As I said before, this is the forth boat to sport a DoelFin. The first 2 were purchased from Mr Doelcher himself. I can't remember what the old installation instructions were, and subsequent installations were done without even reading the new manuals.
ALL my fins were mounted as far back as possible on the anti-ventilation plate. If you have a worse hole shot, more bow rise and porpoising, my guess would be the fin is in the wrong place, since yours got worse and mine got better.
My engine is mounted in the 3rd hole up, and the prop is the std. Vengeance, all as it came from the factory.
As a rule, I don't like WOT. With a 450 lb. load and 2 full tanks our Montauk's sweet spot is about 4000-4500 RPM. With a slight amount of trim this runs at about 23 mph GPS. WOT with a fair amount of trim I get about 5800 rpm and 33 mph, which is close to the published specs. I have NEVER seen porpoising at ANY conditions, with or without the fin.
Edited by gypsmjim on 08/24/17 - 6:59 PM