low rake prop

[Bigshrimpin]

I've been fiddleing about with props again and I'm curious if anyone else has noticed much of a difference b/w high and low rake props. My 20 MA seems to handle/accelerate quite a bit better when propped with a low rake prop. The high rake props I've tried so far rapture + stileto seem to shoot the bow in the air (even when the engine is fully tilted down). The low rake one doesn't lift the bow nearly as much . . . and reduces the stern squat.

[TUGBOAT]

Use a Mirage on my 20 Ma . Gives the stern lift & bow down.
Scream'n Reels'
Tug

[Tarpun]

What size motor and what pitch is the prop. Three blade or four ? I want to replace the alum. 19" on my 20MA with stainless.

[Fr. Frank]

For almost any SeaCraft, with the possible exception of the SeaVette, a stern lifting prop is absolutely the way to go. The overall deadrise at the stern will cause any bowlifting prop to cause to much angle of attack, thus slowing the boat. Very generally speaking, the exception is if you can get the length of the wetted surface of the hull in the water to be less than the 150% of the wetted width.
Thus, a 23' running twin 250 hp motors could probably get away with bow lifting props. Faster top speed, with significant reduction in acceleration.

[muddywater]

I used the search function and was surprised that I did not find more info as far as props go for 20' SC's. For those of us who are not in the know, what exactly do you recommend as far as low rake props go? Lets see if I can summarize what others said about what they are currently using:
Fr. Frank, I believe you said you were running a custom 16.5 pitch/14 dia/3 blade on your 20 Seafari with a 150 Carb Merc. R. Nahim - 17 pitch/15.5 dia Mirage on his 20 with Merc 200, NoBones - 21 pitch LaserII on SF20 with Carb Merc 200. BigShrimpin - 17 pitch/14.5 dia Al Prop with 1981 Merc v225. Bobber - 14.5x19 ss Rapture on SF20 (motor?), HatTrick - 14x19 Al on SF20 with Yammie 150 4-stroke (pitch drop recommended). Recommended prop series appear to be Mirage and Powertech Offshore 4-blade although some are using props I would have thought would be eliminated by the low rake criteria. Are there any other series that are recommended?

[jorgeinmiami]

I run a Merc Mirage Plus 17" pitch on my 20cc with a 200 merc EFI and I seem to run a bit bow down

[Bigshrimpin]

Muddy - I can't begin to tell you how much difference a prop makes in the ride of my boat. I don't like the 17 pitch rapture prop on my Seacraft 20 MA. There was too much bow lift and it was SLOW 44mph max.

I have two other aluminum props . . . cause most of my boating is done in the Sacramento Delta (This week there are lots of trees floating down the river.)

With a stock Yamaha 19" alumunum prop my old 225 can turn 48/49 mph @ 5500/5600 . . . it's got some bow lift but not as much as the Rapture (or the stiletto that was on the FICHT).

The best prop I have is a 14.5" x 17pitch Alumuinum low rake prop Merc Prop. I can hit 47mph and the bow stays down when I accelerate. There seems to be a little stern lift too. I held my prop next to a 17 mirage ($525) at a local boat dealer and the rake is very similar to the Mirage, but the Mirage is much larger in Diameter.

I would definitely get the 17p mirage . . .
one other prop that looks promising is the 17P High Five Mercury.

[muddywater]

Hey BigShrimpin [img]/images/graemlins/smile.gif[/img] I am actually jumping the gun here, but I like to do my research. There is an interesting thread over at continuouswave.com about the High Five props. The general consensus seems to be that they have great hole shot, good holding power, and you lose a bit on the top end. There seemed to be some debate over how high it needed to be mounted. Mounting high seems like it would be a problem for rough water. I wonder how one of those babies would run on a bracketed boat raised up a couple inches.

As for aluminum, I would be buying a new prop every year if I had to go Al. I have hit submerged trees, pipelines, oyster reefs, and even a few submerged cars, boats, street curbs, and fences (Katrina and Rita) and my lower unit is holding up (knock on wood). There wouldn't be anything left for the prop shop to fix if I was using an Al prop. I never really had to worry about rocks though, we don't have any down here.

[Fr. Frank]

Sorry to take so long to reply. PowerTech props makes several low-rake sternlifting props, not too dissimilar from the one they custom made for me. (They cost a lot less than custom props, too.)
PowerTech Propellors
The M250 series have lots of sternlift, but not the best for holeshots.
The UN200FS 4 blades are very good for V6 engines on the 20'. They are quite like the Mirage props.