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"Short Wave Sportfishing" wrote in message
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On Sat, 18 Sep 2004 20:22:09 -0400, trainfan1
wrote:

dixon wrote:




This isn't exactly answering your question but, I have done a lot of
dynomometer work on two stroke outboards. Contrary to popular thought
50 and
100 to one oil mix is detrimental to horsepower gain. In every test
I've run
we get the most h.p. with very rich oil mix. On a recent test, a 50
h.p.
Merc. made an actual 39 h.p. with 16 to 1 mix. When the ratio was
changed to
8 to 1 (yes 8 to 1 ) it made just over 40 h.p. Even at 8 to 1 there was
no
noticable smoke at high speeds. Idle was a diff. story. The extra oil
seals
piston skirts,reeds and between cyl. crank seals. If motor life and
max.
h.p. is your bottom line run as rich oil mix as poss. to a point where
plug
fouling becomes a problem. I have a PWC 951cc. that runs 6600 rpm with
factory set oil injection. With the addition of 32 to 1 premix along
with
oil inj. the rpm is high 6700 to 6800.


Now that is really interesting.

I assume you are addressing the horsepower numbers available at the
prop shaft?

Later,

Tom

Actually no, the readings were directly off the powerhead. I always assumed
mercury under rated h.p. The reason I didn't use prop h.p. is that I put
several hard winter hours testing a mark 58 and didn't feel the need to put
the hours on the quicksilver gearbox. A fresh 50 h.p. four cyl. merc.(44 cu.
in.) is at best 41 h.p. I worked on expansion chambers until I developed
just under 60 h.p. I had over 100 dyno runs recorded. The dyno not only told
peak h.p., but you could plot the h.p. on a rpm curve. On a 12 or13 ft hydro
41 h.p. (stock & quiet) will easily go 75 mph or 79 to 80 with a lot of fine
tuning. Strangely, the 60 h.p. mod motor would never go any faster than 80.
I adjusted the power curve to be making the max h.p. at 80+ mph, but never
could beat the speed I could get with 20 less h.p. The accelleration was
much better than stock though. The next years project was turbocharging the
four cyl. merc. The results were far beyond anything I could have hoped for.
The 1st. dyno run was 85 h.p. With 18 lbs. of boost h.p. was just under 100.
If you are familiar with the porting of a 2 stroke, it would seem that
turbocharging would not work because there is never a time that the intake
port is open that the exhaust port isn't also open. If you are interested,
I will explain later.
Dixon