Yanmar 4JH2E 51hp prop pitch

[Kevin Schick]

Hello, I have a Beneteau 411 with a yanmar 51hp engine and a 3-blade fixed prop. At full throttle I get 3300 rpm. Is this right/wrong? What does this mean - rpm/pitch. Can pitch be adjusted in the water? Also, I am interested in a 3-blade folding prop. Do I need to haul out to replace the props? After I put a folding prop on my boat can it be adjusted for pitch in the water? Thank you

 

[Kevin]

18" 30mm ISO

Hello Kevin, I show that the Yanmar you write about as to having a maximum full load rating of 3,600. If you tack is reading correctly and you are unable to achieve greater then 3,300 then I would suggest you reduce the pitch of the fixed blade by 1”. This should allow the Rpm’s to increase by apx. 7%. If the current propeller is a fixed pitch, no, you will not be able to reduce the pitch in the water. The propeller would have to be removed from the shaft, taken to a prop shop where the pitch would be beat out. It completely depends on the style of low drag prop you buy as to whether or not it is adjustable in or out of the water. I’m not aware of a folding adjustable pitch propeller. You do however have two or three feathering propellers that will allow adjustment in the water, the Max-Prop, Martec and the J-Prop. As a guide for you the diameter of propeller that Beneteau installed on the 411 has been an 18” bored out to a 1:10 ISO taper, to fit the taper on your shaft, three blade. The pitch has been all over the map. It completely depends on the equipped motor and its transmissions reduction gear. Hope this helps. Kevin Woody

 

[Terry]

Kevin, before you consider changing the pitch...

of your prop, what is the maximum RPM rating for your engine? Your engine manual will have this information. I have a 4JH2TE and its max RPM is around 4250 RPM.Once you find out the RPM rating for your engine, the next time you're at the boat warm it up, then in neutral run it up to maximum throttle. It should reach its maximum rating. Yanmar says this will not harm the engine.If it does, do the same in forward gear and see what it reads. If it only gets to the 3300 RPM then something is preventing it from getting to around 3,600 to 3,800 RPM in gear. Verify this with Yanmar.Something else might be going on. Fouled prop, restricted fuel flow, restricted exhaust flow, etc. You need to check these things first before changing the prop pitch.When was the last time you had your engine serviced by a Yanmar technician? It might be worth while to have it done and explain to the tech your concerns. If all this checks okay, then changing the prop pitch might help. Chances are the pitch is not the culprit. The reason I say this is because I have the same symptom, but I can only get 2,500 RPM.Terry