Performance on a 20cc with a 200 Yamaha ox66
 

Does anyone have or know where to get the performance #'s for this setup? I am running a 200 Yamaha ox66 on a 20cc with a 19" prop, turning 5200 and getting 42 knts. Is that about right?

Re: Performance on a 20cc with a 200 Yamaha ox66
 

My 200 merc runs 5600 and 48 with a 19 and a T Top - mine is the XRi which is supposed to be 220 - seems like you should get a bit more, can you raise the engine higher ????

Re: Performance on a 20cc with a 200 Yamaha ox66
 

I guess i will give that a swing, running the cav plate about 3/4" above the bottom, and I have the room on the holes

Re: Performance on a 20cc with a 200 Yamaha ox66
 

Dixon, are you really running 48 knots (55 mph) with a T-top? Man, that's haulin' !! Maybe I'm ignorant, but I'd be afraid of breaking my top at that speed.

Like Dr. Suess said, "Go Dog, Go!"

Re: Performance on a 20cc with a 200 Yamaha ox66
 

Frank - I think he's 48/49mph with the 19 pitch. I seem to remember a discussion about the 50mph barrier being tough to crack.

5600 with a 19p and a 1.87 is in that ball park 48/49mph. 5800/6000 is breaking 50mph with a 19p mirage plus.

Re: Performance on a 20cc with a 200 Yamaha ox66
 

I run an ox66 200hp, on my 21, bracket. I get 47mph @ 5400RPM with a t-top, running a 19p.

Re: Performance on a 20cc with a 200 Yamaha ox66
 

Thanx all, at least I'm in the #'s, will do some tweakin and see what we get.

Re: Performance on a 20cc with a 200 Yamaha ox66
 

Yeah, that sounds right. If I'd engaged my brain first I'd have remembered that.

You're right about how difficult it is to break the 50 barrier. I got my Seafari over 50 mph a couple of times (when I had the Mercury 2.4L), but the weather, loading, chop and everything else had to be just about perfect. My best ever was an indicated 47 knots on the GPS. More normally, I topped out at 42-43 knots. And for some reason, I always pushed the boat to WOT at least for a little while, just to see...:D

I had 1.62 gears (I think, or maybe they were 1.65), with a 15.25"D x 16.5"P custom PowerTech OFS prop, turning 6100 rpms, lightly loaded, with a nose cone, low-water pickup, cavitation plate 2.25" above the keel, running the prop just barely surfacing. With a strong cross-wind, it could get a bit squirrelly at top speed. It was fun, though.

Re: Performance on a 20cc with a 200 Yamaha ox66
 

When I first seatrial my 20cc w/ DF140 Suzuki after putting on the bracket, I was running a 20" pitch Power Tech prop and hit 47 kts- 54 mph. Light load with two people, and it was chine walking :eek: The hole shot sucked, and only turning 5000 rpm. I now run a 18P prop because I wanted a decent hole shot with heavy loads (30 gal bait well, or full load of scuba gear/tanks). Tops out at 40 mph @ 6000 rpm. I may be a little under proped, but for Sebastian Inlet, I really wanted some low end "get up and go".

Lloyd

Re: Performance on a 20cc with a 200 Yamaha ox66
 

well, after reading the pros veiws, I'll raise the engine a notch, see what that does, if it helps, great, if not, I'm done, she was a little squirrly in the ocean, not going that fast all the times anyways.

Re: Performance on a 20cc with a 200 Yamaha ox66
 

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

2.38ratio
20 pitch prop
5000 rpm

= 40mph with no slip

Re: Performance on a 20cc with a 200 Yamaha ox66
 

Thanks for the prop calculator, and keeping me honest.

I miss spoke on my early post. I meant 5500 rpm.

I know the number still don't match, but I remember my GPS hitting 47 Kts (I always keep my GPS set to knots). Of course, that was 6 years ago, and I'm doing this from memory .

My boat was very light, I was still putting in back together, no windshield, no bench seat, and very little fuel.

With that 20P Powertech Prop, it was slow to get on plane, and at WOT, I had the motor trimmed way up. I only stayed at that speed for about 5 secs because the squirliness I felt made me uneasy. I made another run at WOT, and had the same result. I definitely remember thinking that this hull was not meant to go that fast :eek:

I traded the 20P for a 19P the next day, still didn't like the hole shot, and ended up with the 18P I run now.

That's my story, amd I'm sticking to it :D

Lloyd

Re: Performance on a 20cc with a 200 Yamaha ox66
 

Mercury site has a calculator too...

http://appcenter.mercurymarine.com/propSelector/home.do

Re: Performance on a 20cc with a 200 Yamaha ox66
 

6000 (rpm) 18 (pitch)
----- X -------- X (1-10%) (avg.slip) = 38.7 mph
2.38 (ratio) 1056 (constant)

Re: Performance on a 20cc with a 200 Yamaha ox66
 

I think your gear ratio is too low - I think my Merc is 1.87/1

Re: Performance on a 20cc with a 200 Yamaha ox66
 

new 140 Zukes are 2.59:1
older 140 zukes were 2.38:1

Merc 175/200 v6 fishing motor are 1:87
Some Merc sportmaster lowers came with 1.62 gears

I believe I read somewhere that Merc 3:0L gears will fit into a 2.5L case, but I never tried it.

Re: Performance on a 20cc with a 200 Yamaha ox66
 

The GLM catalog lists aftermarket Mercury outboard gears available in 1.5, 1.62, 1.65, 1.75, 1.84, 1.87, 1.92, 1.98, 2.0, 2.06, and 2.3:1, with the 1.5 available only for large 4.75" gearcases, and the 2.3 available only for the 4"/4.25" gearcase. These are not, however, the gears available for the Sportmaster. Those are different gear types. I didn't look at those. The GLM catalog doesn't list prices, just part numbers.

Mercury sells gears for the 4.75" gearcase in 1.5, 1.62, 1.65, 1.75, 1.87, and 1.98:1 ratios,

and for the 4"/4.25" gearcase all of those up to 1.65:1, plus the 2.06:1 and 2.3:1 gearsets, according to my Mercury parts DVD. (And WOW are they expensive from Mercury at about $1000 for a complete set!!!!)

Re: Performance on a 20cc with a 200 Yamaha ox66
 

Did you guys go off on a Merc tangent for some reason when I was sleeping? I'm running a Yami, but will raise the engine a notch this week and will run this w/e, will let you know the results.

Re: Performance on a 20cc with a 200 Yamaha ox66
 

Nah. That was about gear ratios, regardless of make.

Re: Performance on a 20cc with a 200 Yamaha ox66
 

Well you know the old saying...
Once you go black... :eek:..agh, never mind. :rolleyes:

See ya, Ken