What's the right prop for an Excalibur 20'?

[SFC_LEE]

I'm a novice power-boater and I just bought a (2000) Wellcraft-Excalibur, 20' with a 350 Mag Mercruiser 250 HP with 45 hours on it. Bravo Outdrive.

The engine sounded like it was at more RPM than was being shown on tach (just 3000) when WOT and at 51+ mph for just about 10 seconds before I backed it down to cruise at 2200 rpms. Do you think it's possibly overpropped? It comes out of the hole pretty quick, but then it has a lot of HP and I wasn't pulling a skier. Current prop is a 21P, 3 blade S/S was thinking of dropping to an 18 or 19 and see what RPMs show. Any advice? Thx!!!

 

[drivehard]

Re: What's the right prop for an Excalibur 20'?

First thing you need to do is make sure the tach. is right. Next is to use a GPS to confirm the speed.

From the speed / rpm you listed, I would say something is not reading correctly. Either your engine was near to being maxed out, or the speedometer is wrong.

That prop is probably just right or slightly too small for your combo (just guessing) we need more accurate information to make a good call though.

 

[bekosh]

Re: What's the right prop for an Excalibur 20'?

Welcome aboard!
Here's the factory sheet for Sport(bowrider), the cuddy version numbers are the same. The 350 MAG is a 300hp motor and came with a 21p Mirage Plus prop. I would say that your tach is off.

 

[SFC_LEE]

Re: What's the right prop for an Excalibur 20'?

Thanks for the help guys, yes I suspected my tach is off and the prop is fine for this boat. I was concerned about being over proped, but your advice fixed that!

The boat really does perform well, least in my opinion as a novice.
I would love to get the boat's manual, like the one posted, that would be really helpful, any suggestions where I could buy one? I E-mailed the factory, but got no reply in 5 days.

SFC Lee

 

[bekosh]

Re: What's the right prop for an Excalibur 20'?

Goto www.wellcraft.com, click on 'owners' then 'product info guides' for the sheets like what I posted, or 'owner's manuals' for those.
Wellcraft really seems to be on the ball when it comes to providing info on older models.

 

[bekosh]

Re: What's the right prop for an Excalibur 20'?

Since my boat is similar sized and has similar power, 350MAG and 7.4L are both 300hp, here are some performance numbers from my boat for comparison.

With full fuel, 2 adults, cooler, etc.
I run 57.8mph GPS at 4800rpm with a 21p Mirage Plus.

With 1/2 fuel, 1 adult and minium gear.
I ran 59.2mph GPS at 5000rpm with the same prop.

For this year I have a 23p Mirage Plus to run. I'm expecting to drop 200-300 rpm and max out around 63mph.
I won't find out for sure till the ice melts off the lakes, sometime in August the way things are going around here.

I would expect similar performance from your boat with the 21p prop. I doubt that you would be able to go up to a 23p though. I think the 7.4L big block has an edge in torque over the 350MAG small block.