Engine won't get boat on plane - ignition issue?
 

Tried to test run the boat today, and it did not go so well. Idles fine, revs fine in neutral, but when in gear under load acts like it's missing and coughing, not making any power. Acts like an ignition problem - fuel pressure is steady at 5-6 PSI (Holley 800), and no backfires or anything like that. I just can't understand this because this engine was dyno'ed several weeks ago with the same ignition system (Merc 24* module) and ran fine. Nothing was changed on the motor since then - did not tweak timing or carb. Only differences are marine headers with muffled tips, new Carter black fuel pump, and it's now running through the Merc harness. I also ran it through the Merc harness on my startup stand and it seemed to run fine, but there's no way to put a load on it like that.

Things I tried today:

Replaced distributor cap
Replaced ignition coil
Replaced pickup coil in distributor.

Don;t have another 24 module to try right now or I would have done that.

Checked all my grounds on the back of block and couldn't find any that are obviously loose. That is the only thing I can think of right now that makes sense.

I'm getting pretty desperate at this point. Heading to the lake on Thursday for a long weekend. Right now I'm so frustrated and disappointed with this thing that it was tempting to pull the plug when I was floating out on the river. :mad: Kids and wife are pretty disappointed too.

I would welcome any ideas you guys can come up with. Right now I'm so beaten down by this thing that I just want to go to bed.

Budman I have to say your posts make me want to beat my own head in but I have to commend you for putting it all out here and leaving info others may find helpful in future. I have a few merc modules, I can overnight one to you tomorrow if you email me your address. [email protected]

That fockin' thing is going to fight you right to the the bitter end isn't it . You should name the boat " Cursed Cubic Inches " Keep your head up bro you'll be out beatin on it in no time . :angry-smiley-038:

What is your voltage going to the coil while running? If it ran well on the dyno but not in the boat I would look at the variables first, namely making sure the wiring from the boat is in good condition and carrying proper voltage to the coil under load.

bud,can you give me some info,what prop and gear ratio in drive and how old is fuel in the tank?

I was just thinking the same thing as Mike. Could the fuel in the tank have phase separated?

Red, that's a very generous offer and much appreciated! I may take you up on it, but a buddy had a 20* HP500 module. Would that work to tell me if the ignition module is the issue? I know the total timing would be different, but it should show me if it is the issue since it happens almost right off idle.

Mike, I drained the tank and refilled it with fresh fuel today. Running 89 in it which is what it was dyno'ed on. I guess it's always possible that I got a bad tank since that grade isn't used as much, but it sure acts like ignition. You know a lot more than I do, though. Keep the ideas coming, we'll hit it eventually.

And yes, for the record, I am starting to think it's time to sacrifice a live chicken over the bow of this thing to break this damned voodoo curse that is afflicting it.

Should I expect to see a full 12-13 volts on the coil leads under load? It does run a wire off the positive side for the electric choke and as a trigger for the fuel pump relay. Hmmm, starting to wonder about that choke. Might call the dyno shop in the morning to see if they had it energized when they ran it.

Forgot to answer - 23 Mirage Plus with a 1.36 drive. 600 ft lbs should swing that easy.