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View Full Version : Correct prop, and effect on speed at engine idle?


WalloonPS190
08-11-2011, 01:22 PM
Hello,
First post here. Just bought a 2001 ProStar190 with the upgraded LTR 330hp engine and PowerSlot. The prop on it, which the previous owner said he replaced once, is a 13"x14". However, the 2001 owner's manual implies this prop is only correct for the base engine and without PowerSlot, and that this one should have 14"x18" "LC". So I'm wondering if I should try to get hold of the latter. One thing about this boat is that it seems like it's going too fast at engine idle, making docking a bit difficult. Would switching to 14"x18" slow it down a bit at idle? Anyone know what "LC" stands for?
Thanks

FrankSchwab
08-11-2011, 01:59 PM
"LC" means "Low Cup" - the amount of "bend" in the blade (if you put a ruler across the blade, you'll find that it's not flat".

I don't think the prop will have a whole lot of effect on the boat speed at idle. I simply bump the boat into and out of gear to control speed when docking, trailering, or other low-speed operations. Put it in gear until you're moving a bit, take it out of gear and coast, put it in gear to move or turn, take it out of gear, heck even bump it into reverse to slow down.

I'm not a prop expert (send a PM to EJ OJProp (http://mastercraft.com/teamtalk/member.php?u=1537) if you want one of those), but a 13x14 on a PowerSlot boat seems vastly too small to me - like you said, it probably came standard with a 14x18 or 14x20. This prop will probably have a huge hole shot, but your engine will hit redline long before the approx. 45 mph it should run, and will be turning a lot more RPMs that it needs to at all speeds. Unless, of course, you have 3000 pounds of ballast in the boat...

/frank

Jesus_Freak
08-14-2011, 07:31 AM
One thing about this boat is that it seems like it's going too fast at engine idle, making docking a bit difficult. Would switching to 14"x18" slow it down a bit at idle?

Welcome.

Interesting question. It seems that the engine, at idle, is at a fixed throttle setting and is going to put out a fixed energy source regardless of the prop. The energy is available (after friction, etc.) to move a fixed volume of water and thrust the boat forward. So, whether a smaller prop turns faster, or a larger prop turns slower, it seems the thrust will be the same. At higher speeds, other issues come into play, so my proposal does not apply there. Never tested at idle though...

Yes, OJ is the expert.

Cloaked
08-14-2011, 08:23 AM
Hello,
First post here. Just bought a 2001 ProStar190 with the upgraded LTR 330hp engine and PowerSlot. The prop on it, which the previous owner said he replaced once, is a 13"x14". However, the 2001 owner's manual implies this prop is only correct for the base engine and without PowerSlot, and that this one should have 14"x18" "LC". So I'm wondering if I should try to get hold of the latter. One thing about this boat is that it seems like it's going too fast at engine idle, making docking a bit difficult. Would switching to 14"x18" slow it down a bit at idle? Anyone know what "LC" stands for?
ThanksSetting a lower idle is the obvious but you may very well have it set where you want it and it's probably where it should be (~600 - 800 rpm). I'd not worry about the prop as such. Doing that will take away other performance needs (if in fact you have the recommended or chosen prop for your preference).

A solution that works for me:
Technique..... in and out of gear. Forward to neutral, etc.... reverse to dock... etc... let the boat drift and control the speed and direction using the forward-neutral-reverse technique. Once you get the hang of it, you'll be able to steer and dock in any tight area. I use reverse like it's a brake....

.