Motor setup and expectations

You know the drill..

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Bruenar
Posts: 9
Joined: Sun Sep 08, 2019 7:19 pm
Location: Farmerville Louisiana

Re: Motor setup and expectations

#16 Post by Bruenar » Sat Sep 28, 2019 5:08 pm

Update on Motor RPM............. Took the boat out today and max RPM was 4500 with GPS Speed of 21. This was with Trim 100% Down. Trimming up had very little effect on RPM. After estimated 4- 5 trim bumps up on the control, the motor would lose all power and I would shift in neutral and then power back up and the motor would run fine as long as I trimmed back down. The RPM gauge never spiked when loss of power occurred. Motor runs great 100% trimmed down but could not get over 4500 RPMs. The motor is mounted as low as it will go on the boat. My thoughts, based on the above conversations and the countless vids and articles, which could be way off is that I need to lower pitch but how far? Based on Mercury Prop calc they suggest either a 13 or 14 pitch with an increase in diameter. I need the brain trust to let me know thoughts, concerns and more importantly advice.

I have included information on the boat in my signature for ease of reference.

Thanks
2003 Fisher Freedom DLX 220 22 Feet on 26 inch pontoons
2010 Mercury 115HP Optimax DFI
13.5 Diameter 17 pitch Propeller
2.07:1 Gear Ratio
2180 weight
WOT RPM - 5,000 - 5750 in one Mercury manual and 5500 max in another Mercury Manual

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steve1313
Posts: 238
Joined: Tue Aug 22, 2017 6:33 am

Re: Motor setup and expectations

#17 Post by steve1313 » Sun Sep 29, 2019 2:17 am

As others have said, you've most likely got a pitch problem. 4500 is way low for RPM. Do you have a local dealer who will let you "borrow" a couple of different props to let you see which gives the best result?

If not, there are some websites that have pretty liberal return policies. Hopefully someone here can recommend somewhere.
Steve
2017 Sweetwater 2286 WB Tritoon w/ 150HP Yamaha "Serendipity"
Slipped at Lake Anna, Virginia
2018 Tesla Model X

Bruenar
Posts: 9
Joined: Sun Sep 08, 2019 7:19 pm
Location: Farmerville Louisiana

Re: Motor setup and expectations

#18 Post by Bruenar » Sun Sep 29, 2019 3:45 pm

I will check with local dealer and see if they have any I can experiment with. I think I need to drop to either a 14 or 15 pitch. If on average each drop in pitch is 200 RPM then a 14 P gets roughly to 5100 RPM. Mercury indicates 13.875 by 14 or 13.75 by 15 in the Black Max but they also mention a XC. Thats 15.25 by 15p. Anybody have any experience with the Black Max XC over these others?

Based all of the info anybody have a suggestion as to what you would go with? I lean towards 13.875 by 14p mainly because of RPMs needed and larger Diameter gets me a little better control....I think :biggrin2

thanks.
2003 Fisher Freedom DLX 220 22 Feet on 26 inch pontoons
2010 Mercury 115HP Optimax DFI
13.5 Diameter 17 pitch Propeller
2.07:1 Gear Ratio
2180 weight
WOT RPM - 5,000 - 5750 in one Mercury manual and 5500 max in another Mercury Manual

willy13
Posts: 219
Joined: Sat Dec 22, 2012 8:23 am
Location: Canandaigua Lake in NY

Re: Motor setup and expectations

#19 Post by willy13 » Fri Nov 08, 2019 7:52 am

I am late to the party but...

Confirm the gear ratio on the lower unit. Mercury usually puts it right on the lower unit. If its 2.07, I would go with a 13 pitch powertech! WBX3R prop. Its a 14" diameter stainless prop with lots of cupping for grip. It should reduce ventilation issues. I ran this model on my Yamaha F115 before I repowered and switched to a tritoon.

chunkersabre
Posts: 9
Joined: Fri Nov 08, 2019 7:07 am
Location: Lower Alabama & Freeport FL

Re: Motor setup and expectations

#20 Post by chunkersabre » Wed Nov 13, 2019 6:27 am

Depends on what and how firmly you hit it. I boated many years in an Arizona mountain lake, Roosevelt, and it has rocky bottoms and hills that jut up. Hit one of those unmarked "hills" with an aluminum and you might shear a blade. Hit one with a SS and you might bend an output shaft. I also got to know the prop repair guy well, although not as often as you apparently. I carried a spare and both got regular use, and repairs. Got tired of that and got a SS which hit eventually of course. That got me a lower unit overhaul for a bent shaft. That cost far more than several prop repairs or even several props. The hill I hit was probably 1-200 yards from shore, wasn't marked, and very hard. I boat now in NW FL and the bottom is much more forgiving.

Just something to consider.
G3 LX 20 F/C

soon Barletta E24GC

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