Whats this on our prop, and Cav plate depth.
Hi Guys,
We finally got our boat in the water today for its first propper run (charter called it off due to the conditions, so had the whole day) but it went fairly well, just a few questions about a couple of things,
firstly the depth of our leg on the outboard is set to just above level with the bottom of the boat, as you can see by the arrow in the picture when we are running it seems as though the cav plate is a bit over an inch under water, should we lift it by one hole?
Secondly on the prop that the outboard came with (2004 50 hp Etec) there are these lumps on the body of the prop in front of the blades? Does anybody know what these are for? We are thinking that they are just causing drag. It came off a dual setup if that aids in shedding any light onto the matter.
Cheers guys,
Josh
Feral
Posts: 1508
Date Joined: 01/11/06
Looks like a water pickup to
Looks like a water pickup to cool bearings .. not what I'd say was ideal .. and from memory the cav plate should be at hull level
grayzeee
Posts: 2283
Date Joined: 09/07/09
dunno about your prop , but
dunno about your prop , but i've been through all the lifting and dropping of outboard motor on my current boat.
i was sure you were supposed to see the cav plate while on the plane, and lifting the motor would cause less drag.
so i lifted it and lifted again until i was as high as i could go. still couldn't see cav plate on plane , but i did achieve severe cavitation when i thought about turning, got bugger all trim range , and picked up maybe a knot top end.
decided it wasn't worth chasing , and immediately dropped motor so cav plate is level with bottom of hull
next to no cavitation on tight turns and good trim range.
If I spent half as long fishing , as I do reading this bloody forum , I'd be twice the fisherman I am.
holth
Posts: 812
Date Joined: 09/10/06
That props called a 3 hub
That props called a 3 hub exhaust prop which is not made any more and not suited to you hull as its for high performance boats.
You need to prop your engine to suit your hull and optimum RPMs. Your 50hp needs to be seeing 5500/5600 to perform at its best.
As for your engine heigth, lift it up so you can see your cav plate when on the plain and then look for the right prop.
Take a look at these forums for all your etec info. www.etecownersgroup.com
till
Posts: 9358
Date Joined: 21/02/08
Is that the really cheap etec
Is that the really cheap etec that was on gumtree awhile back?
Josh
Posts: 283
Date Joined: 14/09/10
Yeah got it for 2k, but it
Yeah got it for 2k, but it had no control unit
till
Posts: 9358
Date Joined: 21/02/08
Nice!
Nice!
nico
Posts: 226
Date Joined: 17/08/10
Good advice given from holth
Good advice given from holth you will find props with holes in the hub in front of the blade are usually to stop blow out and cavitation at take off and for tight turns this is usually on boats with critical set up for hi performance .Can not say i have seen a cover over the holes like that though.
Mercury props have factory holes which can have a plastic plug put in its place if required to fill the hole.How large is the spray which comes off each side of the cav plate?Does the boat come on to plane easily or the bow ride high and take forever to flatten out?Need more info for suggestions.
In Mocean
Josh
Posts: 283
Date Joined: 14/09/10
Hi Nico, yeah the bow does
Hi Nico, yeah the bow does ride quite high, and only flattens out after a while, which is concerning, as we dont really wanna be riding too high for safety concerns. Wasnt really looking for spray off the cav plate, but next weekend I will take a cople photos to get a better idea. I am thinknig that it may be a trim issue? we might need to have the motor trimmed up a bit?
nico
Posts: 226
Date Joined: 17/08/10
Full trim in when
Full trim in when acceleratung on to the plane and trim out accordingly as you cruise more up trim the more the bow riseses and less wetted surface area.
In Mocean
carnarvonite
Posts: 8673
Date Joined: 24/07/07
Straight edge
Place a straight edge along the hull and see where your cavitation plate sits, it should be level or slightly above the line. Too high will cause cavitation and too low , drag and loss of speed