New guy here! Im gonna start with a running rich question.Ive got a 2000 HP500EFI in a DCB Mach 26.Its got 100 hrs on it and the back of the transon is getting covered in black soot.The boat starts and runs perfect,but at idle you can smell the raw fuel and its making a mess on the transom.It will do it when the motor is cold and warmed up.The water temp is right at 140-150.It actually runs a tad bit richer on one side than the other.Ive done plugs,wires,and cap.I havent checked the fuel pressure yet.It has done it from day one.Could it be the mapping of the ecu?I have heard that the Hp500 is set to run rich but this is way wrong.Any ideas for me...... Johnny Rocket

Are you running Premimum gas 93+ octane? They seem to run with less soot on 87 octane. That seems to everyones mistake at first thinking 93 is better than 87 but from everyones experience this is wrong. Do a search there should be plenty of discussion on it here.

Thanks Ray,

I have tried both 87 and 91.I use 87 all the time but have not noticed any difference in the two as far as soot.Ive tried opening the hatch when starting also.I have heard of trying one step hotter plug range but havent done it yet.I'll do a search and see what comes up.Sounds like a common problem.Thanks again..

Precision Marine 504-469-7463 ask for Mark he has been at the forefront of remapping Mercury ECM's he can cure your problems and very helpfull over the phone.

Also try an extended tip plug,, like a Rapid Fire Part #1 they will help as well. Also add a K and N flame arrestor. Both those will cut it down some.

Thanks again...I tried Mark at Precision Marine but he was busy at the time.I'll call again later.Im thinking it needs the ecu redone.I just want to make sure its not in some kind of default mode before I do.Im going to get the codes ran on it as soon as I can,then get the ecu done..

I have the K and N filter on it.I will try the plugs this weekend.Wheres the best place to find them.

Believe it or not I get mine at Walmart. Definatly get a scan tool on it if you can,,, "limp" mode will do the same thing.

WallMart? ill check into that.It runs so smooth at all times right now.Will limp mode let it run this way?If its in this mode now and runs this good.Ill be excited to see normal mode thats for sure.

How about adding an MSD6M-2 to the ignition system. I did to my 454 Magnum and it cleared up the soot quite a bit.

Yes,I will be doing this soon.Did you do it yourself or not?Ive done other applications but not Mercruiser EFI stuff.Is it hard to do?