Loose spark plugs are typically a sign of detonation. I get worried when I find loose plugs. I don't use a torque wrench but just guessing I apply about 25 to 30 ft-lbs of torque. I run aluminum heads so my plugs are probably different than yours, but with the cast heads I ran R43TS AC.

You really need to do a plug reading promptly after a WOT blast. Sounds like you are plenty fat at idle. A cylinder leak test may tell a lot too, but may tell too much for your liking at this point in the season.

BT

I have a cylinder leak test guage on the way, and will check both motors - for comparison as well as a sanity check.

I'll take a look at plugs tonite, install fresh ones and take another look this weekend after a WOT pass.

Anyone have luck with AC Gold plugs?

BR6FS NGK.......and make sure there tight and checked or replaced after every race!

As I was working on my motor last night changing the oil I decided that the problem is in the fuel system somewhere. If pressure is good, then possibly trash in one of the jets or passages. I am assumming the motor is not getting any hotter then the other one, has correct heads, pistons, & timing is correct..

Thanks again for the tips.

So here's the game plan: Cylinder leak test tomorrow night, and then new NGK BR6FS's to both motors. Plugs tight! New base gaskets for both carbs. While doing gaskets, I'll swap carbs between motors. At least if is a carb problem and I detonate something serious, it'll be the motor I haven't rebuild yet. This will also tell me if the plug problem "moves" to the other side.

WOT runs this weekend and get some plug readings. Assuming things look fine, I'll install the MSD box, billet dist, rev limiter, 5200 chip modules, and wires that are on the way from CP Performance early next week.

My engine shop suggests that I lock down my timing at 34 with no advance, seeing this isn't a pleasure boat anymore. They say this is common in race vehicles, and MSD distributors have provisions to do this. Any thoughts on how this could affect drivability?

If all goes well, that Boatworx Formula has some surprises to deal with in Grand Haven.

Thanks again,
Brian

do not lock your advance at 34 degrees,you could detonate your motors during accellaration,your rev limiters are built into your modules so using msd rev limiters are kinda a waste of money,and they should be limiting at 5350 now,you may also want to put a set of carb spacers under your carbs since you already have them off,usually good for about 10 plus horse on each motor,dumb question,but hopefuuly you used the right head gaskets in you motor right?

I had my HP500++ locked at 34 but I was using a Crane ignition. Never had any problems. The multiple fire feature of the ignition is such that it fires +/- 20 degrees under 2000 rpm if I remember right. In other words the first spark happens at 14 degrees when starting and idling. You will notice that when you try to use a timing light. It will only work for setting the max timing and not idle. Never tried it with an MSD box.

Offshore - these "modules" you speak of... mine are HP500 carb motors, and I'm not aware of any modules where rev-limiting currently takes place. Are you thinking of EFI motors?

Head gaskets were installed by a reputable performance marine engine builder.

The MSD boxes have a similar feature to the Crane box formula21 describes where plugs fire 3 times under 2000 rpm. This should take care of any pre-ignition problems by having more advance on the lower end. How much heat could be created during the short period I spend getting up on plane?

Anything over 3000 is status quo, I'll still be at 34 degrees.

But hey, I'm willing to listen...

Carb spacers are a good thought. Thanks.

on the rear of your starboard cyl head there should be a bracket,on the rear of that bracket should be your ignition module,and programmed in that module is your rev limiting capabilities!as far as locking your ignition at 34 degrees ,all that is is setting your total advance at 34 at 3000,thats the way its sopposed to be done,I may have just misunderstood it to where your ignition would have been at 34 degrees all the time,thats crazy on marine motors in offshore conditions,to much timing with not enough fuel under severe planing loads!