CC247

All else being equal. If I lower my jets one size, as soon as I get on plane my engine temp climbs to 180* and would go higher. I just put one size up in and engine temps stabilize around 120-140 depending on speed. Am I at my sweet spot? Engine vacuum is the same thru all rpms with either jets. Plugs light tan and engine runs good with either. Could it just be running on the ragged edge of lean, or really lean on plane? Confused
One other question, since ethanol has anyone had to richen up the mix?

CC247

ttt

Griff

Did you go back to the 75's and get this to repeat????????

http://www.offshoreonly.com/forums/s...d.php?t=165045

CC247

yes

bcarpman

Certainly doesn't make any sense to me unless the richer jets are just on the ragged edge of putting out the fire completely.

Other than temp, how does it run with either size jet?

Do you have another set of jets in the same sizes? Maybe there's something weird with one of those sets of jets.

Maybe try another set up and down in size and see what happens. That might give us the info needed.

Remember, contrary to popular belief, an engine runs hottest at stoic. and cools off as you go lean. When people say they blew an engine by going lean, what they really mean is that under WOT they needed to be rich and got too close to stoic. (14.7:1)

Regardless, you'd normally be lucky to see that distinct of a change on EGT's let alone coolant temps

CC247

bcarpman- thanks for the info. The carb came stock with#74, then I added emi exhaust that's it. With the #74's it was really lean. I got #76 and runs good. I installed the #75 and get over temp on plane, runs good, no popping or backfires. The plugs look good too. It's hard to tell on the plugs because they don't color as fast as they used too. I have #78 that I'm gonna try and see what those do for me. I'm really just trying to fine tune. The motor runs good gets up and goes well. I just don't want to be lean. I'm sure the emi is not as resrictive as stock manifolds, but 2 jet sizes up is about 7-8% more fuel. Can that be right? Also all of this is happening with the new ethanol fuel. I've heard that it likes a richer mix also.

Griff

I'd say you're right on the ragged edge with the 75's then. I like safe and a little on the rich side is safe. You have to allow for cool low humidity air also. If its tuned in 90* humid weather and you run at 70* with low humidity, it will lean out also.

CC247

thanks, one other thing I did change was the omc spitfire ignition. I installed a regular distributor(mallory),coil,ect.. I set the timing to 10* btdc with 34* total, the motor seems to struggle around 2500-3000rpm getting on plane. I bumped the intial to 15* and the power is back but now my total is 39*. It doesn't ping at all, would advanced timing lean out the fuel mix? Don't mind me, I'm just experimenting with different tuning things and the differences they make good and bad.

Griff

You can't hear pinging in a boat and yes too much timing can cause high cylinder temps.

CC247

I've got the knock sensor that was used in the omc spitfire setup hooked up to my ohm meter and if I hit it with a wrench the meter jumps all over. Thats what I'm using to detect pinging. I'm going testing with more jets. Thanks