HippieCustoms

How much slip should a mirage prop have? I'll explain why I ask. I just did some engine work to my small block. I am running an alpha one with 1.5 gears. With the 19 pitch cleaver prop, before the work, It would turn 4500 rpms and go 51.5 mph. about 4 to 5 % slip. After, it would turn 5000 rpms and go 57.5 mph, again 4 to 5% slip. I installed a 23 pitch mirage. It turned 4800 rpms, and went 58.5. Now that is 15 to 16% slip. So I went out in a friends boat. different hull, different engine, different prop, but still a 23 pitch mirage. His turned 5200 rpms and went 63.5 mph. Still about 15 to 16% slip. Is that just what should be expected from a mirage? Oh his was a bravo one, 1.5 ratio. So I am struggling with what prop I should be looking for. Maybe I need to find a 23 pitch cleaver since the 19 hooked so well for me. Any input on this is welcome. Thanks.

JimV

iTrader: (1)

Is there a nosecone on your Alpha? Those drives are shorter than a bravo and could make a difference. When I installed a nose cone on my Alpha it didn't change speed but it helped handleing.

throttleup

Hippiecustoms,

Different types of boats typically have certain slip numbers we look for. A 36' race cat with 525's may have slips numbers as low as 3-4% with a 6 blade prop. A 38' V bottom race boat may get as low as 7-9%, again with a 5 or 6 blade prop. Slip numbers are a tool we use to determine the proper prop diameter, drive height, # of blades on the prop, etc. Pleasure boats do not have slip as low as race boats, typically. We will generally see slip numbers a few points higher with a pleasure boat of the same hull design as a race boat. This is for a variety of reasons.

I don't think you cleaver prop is really a 19" pitch. What type of cleaver is it? Over hub, through hub (can style) or over-through hub? How many blades and who manufactured it? Has it ever been worked? There are many variables that can change the effective pitch of the prop.

Different style props have different properties. A cleaver prop is a top speed type of prop. It typically doesn't have a good cruise speed or hole shot and really starts to perform well at speeds above 60 mph.

The slip numbers have as much to do with the type of boat as they do with the prop. I would need the information about your boat before I could estimate what your slip should be with the Mirage prop.

Downtown42

http://www.go-fast.com/Prop_Slip_Calculator.htm

I think mine was 10.81% Mirage 3 blade..

HippieCustoms

I am not why I never thought of that, but it makes good sense. The 19 is in the condition it was when I bought it used. There is no way for me to be sure myself if it has ever been played with, but prob has. It is a mercury quicksilver I'll get the numbers off it and post it. As far as the boat goes, it is a wellcraft 216 xl eclipse cuddy. Boat weighs 3300 lbs dry, and I usually have the family with me. Wife and 3 kids. The cleaver I hae now is prob somthing close to what I should need, it just turns 5,000 r's and would like to lessen that, without losing too much. with it on the boat at that rpm it runs 57.5 by gps. of course the lying speedo on the dash says 65..If there is any more info you guys need let me know, Thanks.....