Prop recommendation

[ship happens]

Hello all, active reader yet new poster here. Have an interesting one I have been trying to get to the bottom of. Wondering what some of the experienced prop guys with semi displacement and displacement hills would recommend for this specific application.

Fiberglass semi displacement / displacement hull ( modutech hull) w/ a keel

35 x 12 approx
2inch shaft
2:1 twin disc 506
215 hp doosan (215 hp @ 2200 max)
Approx weight 25000 lbs


Currently running a stainless 3 blade 23p x 26d

Idle speed lugs a bit at static until starts to move. Idles around 4.5 mph nominally / plus or minus the current

Around 1200 rpm it does between 6 and 8 mph depending on current

Likes to run at around 1700rpm at 9 - 11mph depending on current

Will head into a 25 wind with or without the current and be in the same running speed. Sometimes getting down to 8 mph really just depends on current. However will break waves over the bow and doesnt seem to effect it much. Really anything that slows it down is relitive to water current. We are in a very tidal zone in Vancouver in and out the river, plus the tide in the SOG and island areas where the current can run like a river. That being said when going with a 4 or 5 mph current, have been able to get the boat to speeds of around 18 mph.


That all being said, this boat was once a gill netter and now a pleasure cruiser. My question is is the current prop getting the max efficiency? Can I idle slower and gain speed in the WOT? Or is this propped good enough and am I wasting my time?

Thanks in advance

Attached Pic of current prop and running gear

 

[PierreR]

My guess is that you are not going to do much better than what you have. Looks like you can't fit much more prop in that space and your numbers look pretty good

 

[DNT99611]

Will the engine run up to red line plus maybe 50 more rpm? Are you sure about the gear ratio? I ask because I had a 34 foot gill netter with a 3208 and 2-1 506. Prop was 24x15 four blade and that was all the prop I could run. You are turning a lot more prop.

 

[ship happens]

The engine could indeed get to 2100 / 2200 rpm when I first commissioned the boat 3 years ago. I haven't run it up that way since. @800 hours now on the engine, I just run the boat at what it seems to like which is 16/1700 rpm. The fuel pump is really stiff and the cables stretched several times until I switched to 4300 series cable.

100 percent 2:1 506 twin disc gear with a 2 inch shaft

I will add that this boat originally had a 280ish hp Volvo in it. Not sure if the prop was the same as we acquired the boat after the new engine was installed and it never got used after until we acquired the vessel.

 

[ship happens]

Will the engine run up to red line plus maybe 50 more rpm? Are you sure about the gear ratio? I ask because I had a 34 foot gill netter with a 3208 and 2-1 506. Prop was 24x15 four blade and that was all the prop I could run. You are turning a lot more prop.

What hp 3208? What was your idle speed and cruising speed?

 

[DNT99611]

The 3208 was a 210 N/A. I think idle was about 700 rpm, not sure I ever noted the speed at idle. I run her at the top of the green, 2550, and that gave me 13 knots. She would run up to a full 2850 but the pyro climbed quickly so I only did that for very short runs. That high rpm gave me 16 knots.
My first year with the boat I ran her at 2250. I told this to our local Cat dealer, who was friends with my father, and he ripped me a new one. After installing the pryo he wanted me to run it at 2550 and 900f if I remember right. The rpm I know is correct.