Numbers

[Bigshrimpin]

Originally Posted by sidelock

What kind of numbers should I expect to get from a 1975, 18 SF with a 98 Yamaha C115 two stroke & a Power Tip Ballistic 13.5" x 17P. prop. At the present time, I only have a tach., fuel gauge and a volt meter hooked up and have'nt installed any electronics yet since I'm still undecided on what unit to get. My w.o.t. is 5500 rpm as per Yamaha manual.
I primarily fly fish and use the boat on the great lakes & inland lakes as well as coastal near shore fishing for Albies, striped bass & bluefish and a yearly jaunt to South FL. for Tarpon/flats fishing etc.
Any input as well as advice on electronics would be appreciated.

Great Motor! No oil injection on those commercial yamahas. The stock aluminum and stock stainless props on the yamahas are pretty fast (might even be faster than the ballastic) . . . You can play with the engine height, but your doing well with the setup if you are turning 5500 with the 17P prop.

a 17p prop, 2:1 ratio lower, and turning 5500 with 10% slip you'll be at 40mph.

http://www.go-fast.com/Prop_Slip_Calculator.htm

Here are a few archived 2 stroke yamaha 115 performance bulletins. The keywest 186 is very similar to your boat

http://www.yamahaoutboards.com/sites...er-115TLRB.pdf

http://www.yamahaoutboards.com/sites...0111-CEN-Z.pdf

http://www.yamahaoutboards.com/sites...ef-115tlrc.pdf