Prop Question (150 Optimax)

[NFA]

Hey guys, I'm thinking of upgrading the prop on my set-up for the upcoming season. I have a Mercury 150 Optimax on an 18' Maxum, bowrider. I mainly use the boat for cruising, with some water-skiing and pulling, but most of the time is spent getting from point A to B.

I have the stock prop on it right now and it's 14.25 x 17. It works well and I haven't had any issues, except for the typical dings and scratches.

I would like to find a SS one that will up my overall cruising speed and just give me a bit more power. The boat is already moving nicely with the 150, but with an improved prop I think it'll perform that much better. I believe it would improve fuel efficiency just as well.

So what props and dimensions am I looking at, in hopes of improving my top end? Any suggestions on brands, and dimensions? What am I looking for here?

Thanks in advance;


Scott

 

[glengold]

Re: Prop Question (150 Optimax)

I've spent a fair amount of time messing with props. First you want to know what the recommended WOT operating range is for your motor, and where you are currently at WOT.

You need to make sure that the motor is trimmed properly when checking WOT RPMs. If its trimmed down all the way you won't get to max RPM's. Obviously you don't want to be trimmed too high either, then you will over rev... with this information you can decide where you want to go from there.

If you are at the bottom of the range you don't want to increase pitch bc then you will be over proped, and that is hard on the motor.

If you are at the top of the range you can add some pitch, I believe its about 200 RPM's per inch of pitch, so moving to a 19P will reduce WOT RPMs by ~400 RPMs.

I have a lower pitch prop for watersports and a higher pitch prop for cruzing/fishing. This is on a 50hp, 16ft fishing boat. You can move to a four blade if you want better hole shot, it all depends on where you are at and what you want to do....

SS is better for speed and hole shot, but cost three times as much. Also, I like to fish skinny water, and if I hit a rock w/ the aluminum, it may be ruined, but my lower unit should be fine bc the prop took most the force.

If I hit a rock with a SS prop, a lot more force will be transfered to the lower unit, and could damage it, however the prop will probably be ok, and definitely repairable. SS is easier to repair than aluminum, but if you ruin an aluminum you can get another for 80 bucks, and repair will probably run 50 bucks.

Some sites to check out:
http://www.rbbi.com/folders/prop/propcalc.htm

http://www.dansdiscountprops.com/

 

[glengold]

Re: Prop Question (150 Optimax)

another good place to visit:

http://www.acbprop.com/needtoknow.html

 

[Home Cookin']

Re: Prop Question (150 Optimax)

your comments about boating over rocks is a good one. Where I am, we have sand/mud/shell bottoms, so SS is preferred because it handles shells without chipping and sand without wearing out. However, we did sand down a SS from what is effectively commercial use, and over sand.