activox

Howdy, the Mirage 21P that came with my boat had a pretty hard life before I met her, and since I need a backup prop anyhow thought I would just upgrade and keep her for a spare. Also I ran WOT on GPS for the first time last week and was disappointed to only see 42mph at 4200 RPM, I would like to see a little more top end. I think I'm supposed to be seeing low-mid 50s at WOT.

Should I just stick with the Mirage (Mirage Plus) 21 and watch people wave as they go by me, or could someone offer opinion/advice on what I should snag for my new screw that might give me a little more top without completely sacrificing my hole shot?

Current prop is model 48-13702-21 on the inner hub, stamped 48 13702 A41 21P on the prop body.

Thanks!
Aaron

throttleup

Can you please provide us with some details on the boat.

Year, make and model of boat?
Motor make and hp?
Drive Make and gear ratio?
WOT RPM with the 21P?
WOT RPM via GPS?

With a little info we can try to assist you.

Julie

activox

Sorry, I put most of that in the thread title but I'll lay down the works here.

1989 Formula 242 SS - completely stock, no aftermarket adds or mods.

Mercruiser 7.4 330hp / Bravo One (not certain of gear ratio)

WOT (currently) is about 4400 RPM - with a full tank and three people on board best I can get is about 42 MPH on GPS.

The other variable is that I'm chasing an issue with my tilt/trim that is making it hard to dial in, I think I have that whipped now and might be able to squeeze out a bit more speed, but still 42 seems really low.

Thanks
Aaron

throttleup

Aaron,

I have calculated your slip and you have 28% which is extremely high! I would recommend trying some other props on the boat to see if it is indeed a propeller issue. You should be able to run 3B propeller sucessfully with your boat. What is the condition of the props you are running now?

Julie

activox

The prop I am currently running is in fair condition, specs are above. One leading edge has an abrasion on it, and the blade surfaces are in only fair condition as noted before. I would like to pull this prop off and keep it for an emergency backup and am interested in opinion as to what would be a prime candidate for my new screw.

throttleup

I think you are going to have look into some things before buying a propeller. Your slip is way to high. I would recommend that you look at the bottom of the hull and try to determine whether or not something is aerating the propellers causing this high slip number. It can be something as small as 1/16 of an inch of a water pick up or peedo tube, trim tab corner hanging down...well you get the picture. Anyway the 3B propeller should not be behaving this way they typically ran well with the 3B props. I would start with this.

Julie