WOT propellor size next

[simonfraser]

k, exhaust elbow is not bunged up with carbon.

so need to go down in size from B5s on a KAD 44 EDC as i can not get max revs
boat on a trailer, so always clean bottom

B2: full fuel and water tanks:
3000 revs 18.0 knots 04/2019
3600 revs 24.5 knots 04/2019
3750 revs 25 knots 03/2018, Rev Limiter cutting out

B5: full fuel and water tanks:
800 revs 6 knots 05/2019
3000 revs 24 knots 05/2019
3500 revs 29 knots 05/2019 max revs

propellor salesman advised going down one step to B4 as this will give me 250 - 300 extra revs
the J series is more 'modern' and J5 is equivalent to B4

tempted to go down one step further to J4/B3 as i am not interested in max speed

what do you guys suggest i should change to ?

 

[CLB]

In my experience, a change down in size will give you more like 200 extra rpm. So B4 = 3700rpm and B3 = 3900 rpm. I thought max RPM for the 44 was 3900, so not sure why you were only pulling 3750 with B2 props.

 

[kashurst]

I think its says in the manual that the Kad44 should max out somewhere between 3700 and 3900 with clean bum and decent load on board. Every boat is a bit different so setting up props is not an exact science.
The B2s seem about right to me. Clearly works with your boat. Leaves a bit of room for fouling over the summer, and not stressing the engine.
The B5s give a higher speed for a given rpm, but the fuel burnt will reflect that, there's no free rides.

 

[BruceK]

Trailer boat so fouling isn't an issue. Sister boats seem to be running B4's so B3 or B4. Personally I'd go B4. I under propped once. Did nothing for the engines imo. They always felt a bit "loose" and overly revvy.

 

[QBhoy]

Hi. Do you know if it came originally with B5s ? It would be extremely unusual for a VP DP drive to be propped wrongly originally. They are usually almost perfectly propped.