Exciter Prop Advice needed

[gangnamstyle]

Hello, I’m new here and looking for some prop advice. I have a 1986 Exciter I/O, Merc 260, Alpha drive.

The prop that came on it is a stainless three blade 23 pitch. It seems to be to high a pitch under a lot of conditions, works well at high speeds of course but very slow off the line or if you’re cornering etc. I can get about 60mph out of it if the boat is light.

Last season I bought an aluminum 21 pitch, and we successfully ski behind the boat, it’s much better off the line but obviously loose on top end speed. However, there seems to be cavitation, even just in cruising along. Sometimes the RPM’s change and you feel a “surge” or a slow down. I’m assuming this is due to it being an aluminum prop?

My tach is a bit intermittent, and I’m planning on having that replaced before this next season so I can post RPM’s. (It’s electronic and water makes it erratic.)

My question is: would a 22 pitch prop be a better setup for me, and how important is stainless vs aluminum? How about a 4 blade prop, and what pitch in that case?

Thanks in advance for the help!

Sam

 

[karzrus]

The four blade Mercury Trophy Plus props tend to work very well on the smaller Checkmate hulls. These are usually Torque flow hub style so you will need a hub kit( Mercury has more than one propshaft diameter so you will need the right kit) as well as the prop. I would think you want a watertoy/skiing prop in the 19-20 pitch range and a 21-23 pitch speed prop. Having at least two props with you at the lake is useful if one gets damaged - you don't have to stop boating. So I like having a speed prop and a water sports prop. Untill you get the tach working you might not be able to narrow down what is best.

 

[Glenn Kornett]

what type of stainless 23"P 3 blade did you have and what type of 21P aluminum 3 blade do you have and what WOT rpms do they turn? It varies but most stainless props are thinner than aluminum and have a bit more cup (depends on the prop type). A 4 blade will typically pull better than a 3 blade down low but you might lose 1 - 2 mph on top. However, a smaller diameter 4 blade stainless steel in 21"P might pull better than the aluminum 21 3 blade and loose less on the top end than the 21"P aluminum. A Bravo FS in 22" might be a bit too much diameter for your boat (how much does it weigh?) but perhaps a 4 blade 13.75" diameter 21"P Trophy Plus would pull better than what you have now and run almost as fast as your 23"P aluminum. Never know until you try. The Bravo FS is 15.25" diameter and might be a bit large for the weight of your boat. There are other non Mercury 4 blade stainless, smaller diameter props that might work, but the best is to try as many as you can. I have no experience with the Spitfire / Nemesis series but have read that the newer Mercury Alpha 4 blade aluminum barely gives up any speed to the 3 blade aluminum but pulls better. If you had rpm left with the 23P aluminum 3 blade perhaps a 21P Spitfire 4 blade aluminum might do the trick? I think a 22P aluminum 4 blade might work like you said but I believe Turning Point, Solas, and Mercury only sell those 4 blade aluminum props in odd pitches in which case the 21P would pull even better than what you have now, and the WOT speed should be close to now, perhaps 1 mph better if you had rpm left with the 21P four blade. The Trophy 4 blade is a stainless small diameter prop and I think the 21P would pull better than your 4 blade aluminum and have a bit more top end if you had rpm left with your current 21P aluminum 4 blade but do not buy one from what I have said here. You want to get a few to try and find out and then you can often find a good used one for less money.

 

[miller]

I'm thinking we ran a 21" Mirage plus on our Eluder when it still had it's stock 350 in it. It's a 3 blade with good bow lift on the shorter lighter mates.