Need info for re-prop

[Rick]

Hi sailors.
I need some engine and transmission info. I have a Hunter 420 Passage (2004). Purchased 3 months ago. Very disappointed in PO's choice of prop. Think they planned on using the motor as a means of pesky little harbor chores after passages! However in San Diego....

Trying to save myself a trip over to the boat and need info for prop guy.
4Jh2-TE What is the horsepower? Seeing all kinds of answers there.
Rated rpm? It will hit 4000 rpm in gear so assuming 75% of WOT, 3000 rpm would give me? I cant hit hull speed right now at full throttle.
Reduction of transmission? I know it depends but it is the stock unit.
I have as 18 x 12 prop on now. How about yours? Looking to go with a Michigan.

Thanks in advance and happy holidays to all.

 

[JohnShannon]

Well it sounds underpropped. You can redline it and still aren't going at hull speed? What color is the exhaust? Your prop should likely be more coarsely pitched. I think Hunter made a whole bunch of these you are probably on the OE motor and transmission but for some reason the prop got changed? Hunter should be able to tell you what was there originally.

 

[Ron20324]

The prop companies will know your HP and give you the size accordinly. You should look at your tranny to see what it is. "Stock" trannys can be different as the factory may change what they use as the production year goes by. Do not depend on what is on some other boat, because the ratio is a part of the formula for props. What is your engine RPM max in neutral? Propped right, you should be able to get it when motoring.

 

[DayDreamer41]

This may help, as you can see (this right out of a Yanmar Service manual that you should not be able to reach 4000 RPM, definitely under propped, ergo the reason you can't reach hull speed.

SERVICE MANUAL MARINE DIESEL ENGINE 2001.4 4JH2E,4JH2 ...
www.endeavourowners.com/dscsn/info/manuals/4JH2E%20Service%20Manual.pdf

 

[Rick]

Thanks for the info fellas. Mixing elbow is fine. Turbo also. The PO, was equipping the boat for cruising and for whatever reason changed the prop. I am just going to run over and get the data directly. TY.

 

[MitchM]

michigan wheel used to have a free optimum prop calculator on its web site. DAVE GERR'S book on prop design has a lot of info, may be you can borrow a copy. yan mar should be able to supply design data on your engine and your local yan mar dealer may give you some insights. since you have a major manufacturer's boat, can you survey owners of other 336's and see what props they are running satisfactorily?

 

[capta]

Go with at least a 4 blade prop with smaller blades. Less vibration and better power when needed. I've even repropped to a 5 blade (before MaxProps) which increased sailing speed considerably with it's 5 feather shaped fine blades causing less drag and much less vibration under power.
However, you really can't beat the MaxProps if you enjoy sailing without any drag, and powering with confidence. I wouldn't even consider owning a sailing boat without a MaxProp any more.