Merc 3.0lx prop options

[fulano]

Hi Guys,

I'm having a hard time finding info on this in the forums. When I search, is it possible to limit my search to the prop forum? I can't seem to figure out how to do that.


I'm looking for a new prop, and I'd like to get some advice from you guys.

Current Conditions
96 searay 175 br
Alpha one gen 2 outdrive
Mercruiser 3.0lx 135hp
Prop size 14.25 x 17p alum. (a little beat up)


WOT 5200rmp+ @35mph (approx.)
Mid range 4200 rpm @30 mph GPS
Great hole shot (like 3-4 seconds to plane)
A little vibration at higher speeds
Load varies from 700-1100 lbs including gear

Goals:
I'd like to Increase top end speed and midrange speed. I?m willing to sacrifice a bit of low end power and holeshot time. I?m thinking of putting in trimtabs to help me keep as much of that holeshot as possible. I already have a hydrofoil installed.
I?d like to be able to cruise at 35mph at around the 4000 rmp range, with a top speed above 40 mph around 4500 rpms

The standard prop for my boat according to the searay prop matrix is 14.5" x 21p @ 4800rpm, but everything I've read on the forums for this engine says the standard is 14.5" x 19p.

I was considering a 14" x 20p 4 blade.

What do you guys think?

 

[dan02gt]

Re: Merc 3.0lx prop options

The 21P 3 blade is stock on most 3.0L/Alpha 1 setups that have the 1.94 or 2.00 gear ratios. A lot of people drop it to a 19P for better hole shot.

It sounds like you're way under proped with the 17P. Someone may have set it up for wakeboarding or solemn skiing. The prop you have in mind should work ok as would a 19P.

Your trim tab idea is a good one, but I would recommend losing the hydrofoil if do add trim tabs.

 

[MikDee]

Re: Merc 3.0lx prop options

I'd say you need a 13"X19" prop to keep from over revving your engine. I'd recommend Smart Tabs, over Hydraulic ones for your size boat.

 

[steelespike]

Re: Merc 3.0lx prop options

I think a 19" prop would be ideal.Should give you about 4800 rpm and with luck about 13% slip. This calculates to about 37 mph.
Simply removing the foil may add some speed.Of course the 19 will have slower hole shot.
If you add tabs apply them as little as possible.

 

[jestor68]

Re: Merc 3.0lx prop options

Take a look at the Turning Point Hustler 3 blade 14.25 X 19 (aluminum) prop.

Since it has vent holes to improve acceleration time, it should give you the speed increase you're looking for while maintaining a decent hole shot.

 

[fulano]

Re: Merc 3.0lx prop options

Wow! thanks guys for all the responses. So it looks like the 3 blade 19p is the most recommended, but how do you guys feel about the 4 blade? What are the pros and cons? I've read people are opposed to 4 blades on a 4 cyl. do you think I can get the 40 mph top end I'm looking for without sacrificing too much holeshot. Also, I've read nothing but good things on having both the hydorfoil and smart tabs, but most are saying loose the hydro foil. What are are your experiences?

 

[eavega]

Re: Merc 3.0lx prop options

My understanding is that you will sacrifice top end with a 4-blade, and get a better hole shot and low-speed maneuvering. I think its the opposite of what you are looking for. go with the 19p that folks are recommending and add smart tabs for a decent hole shot.

-E

 

[steveobrien84]

Re: Merc 3.0lx prop options

Also have a 3.0 merc on my 180 chap. i had the 14.25x21 went down to a 14x20 four blade. boat runs just under fourty with a little better hole shot than the 21 three blade but the fuel use is so much better with the four blade its problly already paid for itself. but im still in the market for a bettr holeshot prop for skiing & what not

 

[fulano]

Re: Merc 3.0lx prop options

Stevebrien, that's the exact prop I had in mind. What rpms are you running at top speed? Do you have a hydrofoil, or tabs installed. Have you noticed a big difference in handling or powerband at mid range speed?