propeller question

gary111160

gary111160

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25 May 2006
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Boat in Port Dinorwic, North wales
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The standard prop for my boat is 16x13p. Fitted is a mercury marine stainless high five with the following stamp:- 48-821154A45 17p. Can anyone tell me how this varies from the standard prop, and what diference it would make to performance? I don't know from the marking which refers to pitch or diameter. Thanks in advance.

Gary
 
First I am a little suprised by the jump in pitch of 4" from your original to the H5, do you get between 4400-600 rpm? If so all is well.
The High Five will be far superior in performance to the 3 blader you have, I had a similar boat as you and ditched the ally prop for the H5, the difference is that the blades are of a much harder metal so are thinner in section and much stiffer. net result, better acceleration and top speed. Also the blades are more swept so the prop grips much better in hard turns, with no slip or ventilating. The 17P is the pitch, which sounds about right for your boat if it has a 230-260 hp motor, but check the WOT rpm.
I ran a 2655 with the 230hp 5.0LX on a High 5 19P and got 36 knts.
 
Thanks Spannerman.

The boat is currently fitted with the high five and is down on revs by about 600 and flat out gps shows no more than 26 knots on a good day with light load and clean bottom. Bayliner tell me the 16x13 is the standard prop and think my high five is 13.5 diam which compensates for the 17 pitch. They recommend going for a 13x14 for more top end or 13x11 for acceleration. Both these would be ali 3 blades. Do you think I should stay with the 17 pitch high five?

Gary
 
Its not good for the engine to not reach its designed WOT, a bit like driving up a hill in too high a gear, the problem is that it can cause detonation which can burn holes in the pistons, so a new prop is the cheaper/smarter option. I just had a quick look through the Mercruiser prop book and the H5 isn't available in a smaller pitch.
What they told you doesn't make sense as the standard prop is smaller on both pitch and dia, so the H5 being 1/2" bigger dia and 1" bigger pitch doesn't compensate for anything it just loads the engine more so it can't reach WOT rpm, they have it assbackwards!
You have several choices,
Buy an ally prop which will last about 3 yrs.
Buy a stainless prop which will last forever (mine was in the sea for 10yrs continously and was still like new). You can get a 3 blade or poss preferably 4 blade.
Or see if one of the prop specialists can tweak your existing prop, shaving the extra 1/2" off the dia will bring the revs up, and maybe tweak the pitch, but you would have to talk to them to see if its poss.
If you go for a new prop I would strongly suggest you go to a decent boat workshop as then they have to lift/slip the boat or hang over the swim platform to fit the prop and if they get it wrong they have to try another until they get the WOT right, and you only pay for one prop! If you buy it over the counter, and you have change the prop they may not take it back once fitted so you could end up with props you don't need.

Good luck. Steve
 
Thanks Steve very helpful.

The standard prop bayliner recommend is 16 diameter and 13 pitch, sorry I may have misled you with that, not the other way around so the current h5 i have is 2.5 inches less in diam. and 4 inches greater in pitch.

Regards

Gary
 
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