I shoot for the 6000 to 6500 range.
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I shoot for the 6000 to 6500 range.
I have raced up to the mid-6000s or so. You will need a different pack to get rid of the limiter. Look for one that does NOT have the number 6100 printed on it.
No experience with these, but downloaded this pic from BRF a couple years ago.
As far as I know, all the sizes are available, so from 59 down to 58. I don't think there's any advantage to going up to a larger jet, unless you're not getting enough fuel where you are now. More...
The standard from-the-factory jet varies over the years. I've found slight improvement going down one size from that factory jet. Two sizes smaller and the motor falls on its face from idle, but...
These are the basic measurements I've taken. Although the '70s vintage carbs are slightly smaller in some measurements, I have raced them with no noticeable ill effects.
We race these motors in GT Pro class in MN. To upgrade a 25, we just bolt on the big-bore carb and leave the 25 intake in place. In fact, the only test I'm aware of got slightly faster top with the...
I've made mine 20" high. If you mount the motor directly on the motorboard, that turns out to be a reasonable height. If you add a jackplate with a few inches of setback, there's room to go up...
My experience with small (35hp GT Pro) v-bottoms is jack it up as high as you can without losing water pressure. For a 31.8 OMC without low water pickup, that ends up with the prop shaft about 1.5"...
Racing GT Pro (OMC 32.8, 30/35hp), I've always had the best results running in the 6400-6800 rpm range. However, the 20hp version of this powerhead is seriously restricted at the intake, so results...
Try Tim's Outboard in Hackensack, MN. 218-682-2331. They have a large inventory of used parts, and they ship. Make sure the pack does NOT have "6100" printed on it -- that's the limited version.
"Rapair" makes CDI modules for outboards. Look them up on Google and a number of dealers will come up. Or if looking at used ones, any 2-cylinder OMC pack with connectors compatible with your...
If the power pack is rev limited, you will see the number "6200" printed right on it. And if you do have one of these packs, there is no question about it when you hit that 6200 rpm.
We race...
That's right, which is why I said "unless you are upgrading a 20hp." The 20 intake is very restricted.
For GT Pro we simply upgrade the carb and don't bother with the intake (unless you are upgrading a 20hp). One racer did compare intakes and got slightly better results with the 25hp intake.
One...
You could build your own jackplate. http://www.dillon-racing.com/jackplate/index.htm
You might consider using 3/8" aluminum for a motor more than about 130 lbs.
I tried it. I didn't read any pressure on a gauge with 35psi max. I currently have a tube running to the cockpit to monitor water flow. I need about 3000 rpm to get any flow to the end of this...
Brent tested his system and reports that it "worked great!" He says he achieved 50 mph with a 30/35 OMC on his Dillon Mini Vee.
http://www.dillon-racing.com/customerboats/Compton/
I got an email from one of my customers this morning. He has set up a trim system on his Dillon Mini Vee using a trim-tab actuator. He hasn't tested it on the water yet. I will update when I hear...
So that's a yes? Strong enough to be used in a setup like this?
Is the Lenco actuator strong enough to be used in place of a hydraulic cylinder on a "regular" trim system -- at least on a small (25hp - 40 hp) motor?
I had a similar problem, minus the back firing. Was difficult to start and had to partially cover the carb throat to smooth out the idle. Turned out to be a bad bottom seal. I assume a bad upper...
It's certainly true that there is no problem with 35hp. I've also tested with a 40 Nissan/Tohatsu (2-cylinder). Went 50 mph and showed no signs of excessive bow lift. Beyond that I couldn't say.
...
Mark,
Will you be bringing your Sport C to Minnesota to race next summer?
I forgot to mention: we don't use any springs in our steering systems. Shape and/or postion the steering arms so that the ends -- where the cable attaches -- are in line with the engine's tilt...
We run steering cables direct to the steering arms in our smaller OPC classes: Mini GT (25hp); GT Pro (35hp); and Sport C (40hp). I use 5-inch steering drums on my boats, which makes for very quick...
It sounds similar to the 20hp intake, the top one in the photo below (the lower one is 25hp). I assume the slot is to allow fuel left in the carb throat to drain back into the intake. A low,...
It looks something like this:
Also, the 1976 35hp had points ignition, all since have been cdi.
http://www.dillon-racing.com/images/Picture%20014b.jpg
1977 was the first year OMC used the 31.8 cube powerhead for the 25hp. But it was over-the-prop exhaust. Went to thru hub in 1984 or 1985.
The only rev limiters I've seen are built into the power...