Prop decisions

[Faerbairn]

1991 4.3L v6 mercruiser
Alpha One Outdrive
1991 Sea Ray 170

I have 3 props to choose from. I want the one that will give me the best skiing performance.

My choices are:
14 x 19
14.25 x 21
and one that say 48-78120-19
Option 4: Is there a better one?

Thanks

 

[steelespike]

Re: Prop decisions

You have 2 19" and one 21.Assuming all are 3 blade and the same design and material the 19"s should give better hole shot.You will have to watch that you don't overrev with the them.Usually a 4 blade is the best for hole shot and improved low to medium performance.I would test them all and make a decision from there.
If you get us the figures (max rpm and speed, hole shot, performance impressions)we may be able to help you pinpoint a prop.

 

[CharlieB]

Re: Prop decisions

The Merc prop is also a 19 pitch, but the blade design may not be the same as your other 19 pitch propp and can run noticeably different.

With that out of the way, selecting a prop for sking often requires significant improvement in holeshot so you can get the skier up out of the water without dragging them halfway around the lake.

Many people under prop their boat to get this type of acceleration at the expense of loosing a lot of top speed.

The risk in doing this is WOT RPM can run too high for engine longevity.

Where Merc recommends a WOT RPM of 4800 - 5200 is ideal for engine longevity, skiers often select a prop of 2 inchs LESS pitch and elect NOT to run the motor at WOT except for the moment needed to get the skier up then pull back to maintain a comfortable ski speed without harming their motor.

You will need to test each of your props to determine their WOT RPM and holeshot characteristics to decide which is best for YOUR use.

The 19's are most promising BUT may still be too much depending on your boat loads plus a skier(s). You may need to drop to a 17 or install a 4 barrel carb/intake for a few added HP.