Advice on propeller selection

[Slimy Salamander]

Hi guys,

I bought a Linder Arkip 460 aluminium boat in January with a Honda BFP60 engine. This is the 60HP engine with the big gear case.

The engine only revs to 4750RPM when it's carrying the usual load with two persons. This is far below the 5500 and 6000RPM as specified for this engine.

The current propeller has a diameter of 13-1/2 inches and a pitch of 15 inches.

I obviously need a propeller with a lower pitch, but I lack the experience to make an educated guess.

Does anyone have some advice on a propeller I can get to bring the revs up closer to 6000?

 

[Rory]

go down to 13 pitch props that will in crease your RPM

 

[Slimy Salamander]

Thanks Rory, a distributor of props also suggested a 13" pitch to increase the rpm, but since there is such a massive deficit we've also been considering an 11" pitch.

 

[Rory]

11 is very low for such a small light boat  i fit 11 on the merc 60 to push big 1.5ton barges have a look at engine hight aswell maybe you can lift it a hole or 2 and this will allso help with RPM

 

[Slimy Salamander]

Yes, if the merc with an 11" can push a 1.5 ton barge then it's going to be too low for my boat that weighs less than half that unless the higher altitude here (±1300m) will have such a massive effect that it should be propped lower?

My boat is from Cape Town and the shop selected the prop and since then I've replaced the 50Ah battery with 200Ah as well as add a trolling motor.

 

[Rory]

altitude does play a big part and you will feel the differance at sea level post a picture of the motor trimed in from the side so i can have a look at the hight

 

[Slimy Salamander]

Rory, thanks for the advice so far, really appreciate it.

There is still one adjustment hole left to lift the motor for the two bolts at the top, but the problem is that the bottom two bolts are already at their maximum adjustment.

Here's two photos:

 

[Rory]

does not look to low put a straight edge on top of the cavitation plate above the prop this should be 20mm lower than the bottom of the transom.

 

[Slimy Salamander]

I measured it and it's about 20mm below, so that is spot on at least.

It's all about guessing the pitch now. I'm not sure how easy it would be to sell a prop so I would like to guess as close to the correct pitch as possible.

 

[Rory]

keep that one as spare and get a aftermarket one alu props dont last for ever

 

[Slimy Salamander]

I'm going to get a 13" pitch and see what happens and then when the time comes to change props again I'll decide between getting another 13" or going a step down to 11"

Thanks for all the help Rory, I'll post the results of the 13"

 

[Slimy Salamander]

Forgot to update, the 13" prop is the perfect match. Goes to 5950-6050 RPM and top speed increased slightly as well. Very happy with the performance now.