Max Prop

[Paul]

I have an 1987 30 with what I assume is the factory installed two-blade fixed prop. I'm considering the idea of replacing it with a three-blade Max Prop. Has anyone either tried this or heard what the perfomance gains/concerns might be. I'm assuming going from a two to a three blade prop is going to make a noticeable difference in forward, but does the boat suffer from a more exaggerated prop walk in reverse?Thanks in advance for any info.Paul

 

[Joe Barrett]

Feathering prop

Actually Paul, the opposite is true, prop walk is virtually eliminated with a feathering prop. The reason is on a fixed prop the leading edge is always forward. On a feathering prop the leading edge reverses itself when it spins in reverse and prop walk is eliminated.You will not believe the solid power you will get in reverse, be careful you need to get used to the increase in speed when backing! In terms of forward thrust it is about the same, On my C320 I still get 7.25 kts. at 3600 RPM which is max I ever got out of my fixed 3 blade.Your performance while sailing however will be much improved particularly in light to moderate air. I had a 2 blade folding prop on my last boat, reverse was not as good as the fixed, speed in forward I lost about 1/2 kts over the fixed. The pain was when racing you had to go below to the shaft to make sure it was lined up right so the folder wouldn't drag open with gravity. No need to do this with feathering prop, you shut off the engine at full throtle so the prop feathers open and that's it! BTW I have the Autostream 3 blade feathering prop from Martec, I've heard good things about the Max Prop except that you cannot change the pitch in the water.The prop has to come off and disassembled to change the pitch, on the Autostream you can adjust the pitch in the water.

 

[Rick]

I have one...

... on my '89 MKII C-30 with the Universal 25xp diesel engine. It is a 3 blade max-prop.Joe is correct that all the performance gains will happen while sailing and while motoring in reverse. Motoring in forward is a different story. The Max-prop has flat, ineffecient blades and you will probably not be able to motor as fast as you do now. My boat lost about .5 knots of speed off of the top end and will barely cruise at 6kts at full throttle.Increasing pitch (which requires a haulout) causes to engine to labor at less than full rpm and results in high temps and exhaust smoke. Decreasing pitch results in a better running engine but slower top speeds.If you buy a Max-prop plan on 3 haulouts while you experiment to find the best compromise of pitch settings. Joe says that his motoring performance stayed the same. Keep in mind that he has a C320 which uses a 16 or 17 in prop and that he is NOT using a Max-prop but an Autostream. The Autostream has properly shaped blades (not flat) and has the advantage of being adjustable in the water.I feel that the Max-prop was a mistake on my part and if I were able to do it all over again I would have been happier with an Autostream. Unfortunately, I am not sure the Autostream is available in the 13" size needed for a C30.

 

[Guest]

To Rick on Prop's

Rick sorry you don't like the Maxprop. I didn't know of speed lost in forward gear. My speed with the Autostream is exactly the same as the 3 bladed fixed. I do however have a 15" Autostream prop. One reason I bought the Autostream is I bought a new boat and was not due for any haulouts.Although Martec does not recommend this I had a very experienced diver install the prop on the boat while in the water. He did have to also come back to adjust the pitch, again right at my dock.Here is the link to the Martec website, I don't see any feathering prop smaller than 15" but worth a phone call, they are very knowledgeable about props.Autoprop, Gori and Flex O Fold also might work. I have heard that to use the Autoprop on the C320 you have to change shafts from the stock bronze to stainless steel.Joe Barrett