Prop Slip Symptoms

[Sabre]

I've just put a reco prop on (14.5 x 19) as spec by manufacturer.

I suspect the hub may be slipping, because out of the hole it seems to over rev, then it get's going ok, and then at WOT speed seems to be down, and revs too high.

I've marked the prop, hub and spline for my next trip but I'm curious to get other opinions.

Thanks
Sabre

[stinky-stabi]

sounds like its cavatating ? my 2 cents worth..as if you have had the boat for a while you know its characteristic so it wouldnt be the the trim????

[Sabre]

Only just got it, and only been out twice, so I dont know the characteristics of it as yet......

[stinky-stabi]

well i would be having a good old play around with it and see the out come ,,, if you have not had much boating exp?? take some one who has, maybe they can help you sort it

[cormorant]

Airation can do that. Some props are designed to airate on holeshot and generally have a small hole on each blade near the hub. It gets teh prop spinning and into teh motors preferref torque band earlier.

Marking the hub is a good idea , scratch it in as we have done it with paint before and it wears off very fast.

Was your WOT easily reached and did you bounce off your rev limited, if so it may be too lower pitch or diameter. Actually measure the diameter as some prop workers will trim them to clean them up and add pitch Not ideal.

[Moonlighter]

Hi Sabre

I'd be very surprised if the hub is slipping. I've had them go and when they let go they will not grip enough to take the load required to get you onto the plane. All you get is massive revs and it won't plane. So its almost certainly something else.

You said something in your original post that caught my eye about the prop you've put on being "as spec by manufacturer". Can you tell us what you mean by that? This is because it's a bit odd to have the outboard manufacturer recommend a particular prop for a specific boat - does happen, but not that often and fraught with problems because every boat is loaded and used differently, therefore dfferent props may be required.

In the meantime, here's a link to an article that should help you figure out if the prop you've got on, and the motor height, are correct for your boat/motor combo.

[FONT='Verdana','sans-serif']Engine height on the transom has a huge impact on your boat's performance - acceleration, speed and fuel economy all impacted. In fact, you could already have the correct prop but if the engine is too low or too high, it could be the one thing that is limiting your performance.

See this link, it really is worth a read and a look at the pics:
http://www.veradoclub.com/smf/index.php?topic=137.0

It includes excellent pictures taken when the boat is at speed to show you how a cav plate looks when its too deep and when its at the right height.

It also tells you in very precise and easy to understand terms how to do a test to determine if you have a prop fitted that suits your boat/motor.[/FONT]

Hope this helps

ML

[Sabre]

Moonlighter,

Thanks for the info. The spec I referred to was from the manual for the motor (14.5 x 19"). I read this article on Monday and will be checking engine height also, as I suspect the engine may be too low. It's a very good article and should be helpful to all.

Cheers
Sabre

[Noelm]

the manual will state the prop that was packed from new, has nothing to do with what may be needed later, almost certain the motor will not be too low if you have vent problems, you will need to "borrow" a few props if you can to find the correct one for your boat, you will need to select one that will allow max RPM with a "normal" load, but naturally you need to ensure your motor is set up correctly before you start fooling around, or call a prop specialist company that will help you out.