Re: 2008 115 4stroke Idle rpm
I just replaced 81 115 2stroke with 4 stroke. Had to downsize 20p HiFive to 17p Trophy Plus. This on a 17" Boston Whaler Outrage. So far so good.
But .... this 115 4 stroke Idles at 850 rpm where the 115 2 stroke idled at 600 rpm. My fish troll speed now is close to 3mph (gps) and is too fast.
Merc dealer says the 850 rpm idle speed is fixed and cannot be lowered/reduced at all or to 600rpm. Is this true or false?
Is there any trick to accomplish this? Rumor has it that it can be done.
Thanks....Chili
Here is my answer to this (my) problem. It turns out that my Idle speed is 738 rpm, The engine spec is 700 rpm +/- 50 rpm....so I am high, and I can't change that. My estimated 17' Whaler Outrage weight, all fish gear with 2 Adults and 18 US Gallons fuel is 2400 Lbs, OK Canada that's 1088Kg.
So, I just bought another prop...a Merc Vengeance 14 pitch (pn 48-17314 A46) I was at 17 pitch and now 14 pitch. Simple math says this prop wud be 82 % of the speed of the 17 Pitch prop. So, here are the results of my test last week.
MERCURY TROPHY PLUS PROPELLER - 17 PITCH
13 3/4" diameter, 4-blades, stainless steel construction
Quicker hole shots, great speed
Dramatically improves handling and reduces steering loads
Applications: Outboards 75 hp and up
Comes equipped with the Flo-Torq II hub kit
Performance Vent System with large vent fittings
Model No. 48-825930A46
-------------------------------------------------------------
MERC VENGEANCE PROP - 14 PITCH
MODEL 4817314A46
Comes with Flo-Torq III hub kit
13 3/8 diameter, 3 blades, stainless
17 to 14 pitch is 82% 2.8 mph shud go to 2.31 mph.
13 3/4 inch diameter to 13 3/8 dia is 3% smaller.
Test done July 8/2009 Trophy versus Vengeance:
................................................ Trophy.............. Vengeance
Idle speed (738 RPM).........2.95 mph .............2.35 mph
Speed at WOT .....................35 mph................35 mph
RPM at WOT........................5000 rpm.............5900 rpm
I do have slight (very temporary) cavitation on full load take off but I can live with that. The good news is I now have my fishing trolling speed and my WOT rpm's are good to the factory spec (5900 t0 6300 rpm)
AMEN...... Chili