Is a 4 blade what I need?

[Vroom_vroom]

So I now have Completed my outdrive overhaul and I’m looking at props again. I went from a beat up 21p to a 19p and it rockets my little boat out of the hole with the 3.0 however it has the potential to over rev if I where to let it. So I am back to looking at the 4 blade props again. Wonder what the consensus was on going to a 4 blade and is there any economy difference?

long story short I like the fact the 4 blade had less blow out, and less wander backing up (in my experience) would it drop my rpm 2-300 @ wot and help with top end speed? (Concerting Aluminum to stainless)

the boat is a 90 maxum 18ft open bow, 3.0 met cruiser with smart tabs.

 

[Scott06]

Consensus is hard to find... prop choice depends on how you use the boat. I have run 4 blades on my last two boats because majority of my use is taking my daughters and their friends waterskiing, tubing, or wakeboarding. In my experince I get better holeshot and lower planing speed at the loss of some top end. Top end I find somewhat useless as I rarely get to use it.

Id try an 18" 4 blade, I ran 18" Michigan vortex on my 17 ft 3.0 bowrider with very good results. As for economy, you have just about the least fuel thirsty engine out there, what prop you use won't move the needle, but throttle position will.

 

[QBhoy]

21” laser 2

 

[Texasmark]

Google what you want to know besides visiting here. Mercury and Turning Point, to name 2 prop makers have extensive information out there concerning their props, the whys of the designs, and applications. If you are really in doubt, find yourself a loaner prop shop that loans props for testing before you buy.....from them. Will give you expert advice and save you a lot of time and money "in the long run". Wink!

 

[wahlejim]

How much over RPM are you with the 19 3 blade? How was the boat loaded? How will the boat be loaded during normal use?

If you are close with the 3 blade, use a 4 blade 19 pitch. By close I mean a few hundred RPMs, if you are 500 or more over, go up to a 20 4 blade.

 

[Vroom_vroom]

I have a turning point 3 blade 19 on there now(that’s what I would buy again). I don’t know how far over I could run it but at wot with 3 guys an ez up and the other unneeded crap we take day camping I can run 4600 rpm @ 3/4 throttle. Topping out at 38 mph. Really just thinking about a better prop to match the rpm window. A ss prop is what I keep looking at but a ss 4 blade I think might be too much. The beat up 21p 3 blade wouldn’t even make it to 4K rpm

 

[Vroom_vroom]

Between 2-4 people with all our day camping crap cooler ext. is the normal load.

 

[Scott06]

You may want to check your tach vs a known good shop tach. The spread between the two props doesn't seem right, and I'd be surprised if a 19" would over rev a loaded 18 ft boat with a 3.0. I had a 3.0 many years so I mean no disrespect to your boat, but I wouldn't spend the money on a ss prop as a 3.0 doesn't have enough power to take advantage of it. Plenty of good al props out there for way less money.

 

[Vroom_vroom]

Fair enough. The one I have checks most of my boxes, need to double check the tach accuracy. I pulled it apart and cleaned the hell out of it this year and it’s been working like a champ but if it’s reading low it’s reading low.

 

[Toyelectroman]

I would be careful relying on the gauge tach for an accurate reading. My brand new boat off the dealership the gauge tach was reading 6300rpm but my mercury vessel view only had it at 5800rpm

 

[WesNewell]

I would be careful relying on the gauge tach for an accurate reading. My brand new boat off the dealership the gauge tach was reading 6300rpm but my mercury vessel view only had it at 5800rpm

Check the switch setting on back of tach. Same thing happened to someone I know it it was set wrong from the factory.