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Author Topic:   Merc 75 Prop on 15' Dauntless
huladick posted 08-07-2001 08:34 AM ET (US)   Profile for huladick   Send Email to huladick  
When I bought the boat, it had a Merc "High Five" Stainless Steel prop. 5 blades is unusual for me. Seems hard to get up on a plane, even with just 2 people. Tried all trim angles. Any suggestions for another prop ?
jameso posted 08-07-2001 11:29 AM ET (US)     Profile for jameso  Send Email to jameso     
Dan, As a general rule the less blades on a prop the faster the engine will rev and the faster you go. I have a OMC 50 on a 15 sport 3 blade aluminum and it will scare you jumping on plane and the top end via gps with one aboard is 36/7 mph. Look at the posts in Post classics for some older prop questions and there is a reference to Nettles prop shopin Austin TX, also,,,our expert in residence Clark with the Spruce Creek Navy has a great post on this board concerning HP/Weight ect.
Bigshot posted 08-07-2001 11:38 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
your lack of holeshot seems to be due to too much bite. A 2 stroke needs to rev a bit to get the torque to plane quickly. Does the prop you have have ventilation holes(near the casing, behind the blades) that are plugged? If so remove the plugs and try it.
huladick posted 08-08-2001 02:06 AM ET (US)     Profile for huladick  Send Email to huladick     
Thanks to you both for the info. I am new to the Dauntless, but love it already.
Clark Roberts posted 08-08-2001 09:53 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Hula, the "high 5" comes a pitch range that starts at 20" so you have at least a 20" pitch and maybe more... most likely too much pitch and even with the vent holes not enough hp. The 75 Merc with right prop should be a very good performer... You should check your wide open throttle (WOT) rpm and make sure you get a prop that will allow you to reach 5250rpm with light load if it's a 2 stroke and 6000rpm if it's a 75hp 4 stroker... good luck.. Clark.. The Old Man and the Sea
huladick posted 08-09-2001 01:00 AM ET (US)     Profile for huladick  Send Email to huladick     
Thanks Clark...

I'll check the rpms this weekend.


huladick posted 08-13-2001 09:28 AM ET (US)     Profile for huladick  Send Email to huladick     
Checked rpms this weekend. WOT, I got 4800 rpms. Prop# says it's a 20p. Hole plugs are removed. Any suggestions on a prop with better take off and quicker plane ? Thanks
Clark Roberts posted 08-13-2001 09:32 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Hula, generally one inch of pitch will net you 200rpm either up or down, so if you need to pick up 450rpm (in the case of a 75hp Merc 2 stroke- 5250rpm max at WOT) ... My guess is you need a prop with 2" less than the 20" pitch "high 5"... a 3 blade,stainless, double cup prop with 17-18" pitch will do the trick.. Merc makes good general purpose and specialty props and there are some good aftermarket props like Stilleto and Power Tech... in any case you should try before buy as the right prop is so important! Good luck and happy Whalin... Clark.. Spruce Creek Navy
huladick posted 08-14-2001 09:22 PM ET (US)     Profile for huladick  Send Email to huladick     
Clark... Thanks for the info. I'm kinda new at this prop bizz. Do most places let you try them out first ? The High 5 was on the boat when I bought it. It looks cool, but doesn't perform real well. Thanks again.
Dick M.

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