2001 Mercury 150 saltwater running rough

So my new to me boat is running rough under load. Basically it feels like a misfire when i am trying to get on plane. after it chews through it the boat runs fine. no issues with starting it, no smoke, no indication of carb or reed valve issues. plenty of battery and it has good gas.

i put new plugs in it and made sure they were spaced out according to the mercury plug chart i found. also i replaced the fuel filter that was four years old. no gunk in it so i assume i dont have a fuel line issue from ethanol damage.

FYI the tachometer does not work. I called a shop and the guy mentioned to me that I may have an issue with my voltage regulator. not sure if the two issues are connected though. Ive noticed that with more people/gas int he boat the problem is worse. i dont want to tear anything up by continuing to use it and I cant afford to re power it.

any suggestions? any boat mechanics here who want a side job?

not sure if it matters or not but I think i have an issue with the gas tank. when i fill it with gas i get a back draft of gas and sometimes it spills out onto the ground. my only resolution is to put about 3 gallons in and then take the nozzle out for ten seconds and let some air out so it does not gurgle. sometimes you can hear it gurgling in the gas line. if ti gets backed up all the way gas shoots out everywhere (like 2-3 feet of pressurized gas). is there supposed to be an air valve to allow air into the system so it wont gurgle? not sure if these issue are related.

also the fuel bulb always seems to be hard. no issues with a leak that I know of.

Try posting this over at BBC Mercury motro section. There are a ot of experts over there that may help.
Link :: http://www.bbcboards.net/forumdisplay.php?f=8

i will. thank you. anyone on here have any advice as well?

there should be a pressure vent somewhere for the gas tank, mine has a rubber hose running to a small vent on the top of the boat. They can get plugged up and sometimes the hose will sag and fuel set in it and plug it, you can blow it out with air.

That could cause motor to starve for fuel under load.

Also, is the fuel bulb hard from fuel pressure or from age? It should be soft enough to squeeze after pressure is released. If you replace it get one with the double valves, lots of cheap ones for sale with single valves....

What plugs are you running? I am not sure but I thought all the carbed V6's ran surface gap plugs, usually Bu8h, BUT SALTWATER VERSION MAY BE DIFFERENT....

the bulb appears to be pretty new. its not faded or anything. it is still soft rubber.

I may try to pump it while the boat is trying to plane out. if it is a fuel supply issue that may tell me something right away.

ill look for the pressure vent asap. I'm pretty sure the gurgling issue is caused by lack of ventilation. its on a center console so I'll probably start under the console looking for it? it has a built in fuel tank that I cannot see.

keep in mind though that it will eventually get to WOT and acts fine. its just getting it to that point where the issues are.

ill check on the plug #. i found a different plug than what was cross referenced (used NGK). it was the same depth and I just had to space them out. it looks identical to the NGK ones i took out. same issue as before the new plugs though and no noticeable change.

I edited post above about spark plugs.....

The vent should be up fairly high on the boat to keep from getting water in it.

Check if there is a fuel filter, it could be partially plugged causing it to bog and then catch up.Ethanol fuel is hell on these fuel systems.

Thats interesting, it would be good to find mercury's reccomended NGK plug for that motor, I just found that v6 150 motors serial #0G960500 and up run a plug gapped at .040.... and I would never run Champions......

i gapped them at .040 plug is identical with a different # on the side. i will look for the originals though.

also I replaced the fuel filter. the old one looked fine though but was old as indicated by the writing on the side from the former owner.

ok, check the tank vent and try pumping bulb when it bogs, if pumping bulb fixes it fuel pump may need rebuilt.

just reread original post and voltage regulator could cause this problem also...

I have a 02 , 125.
When i had a similar issue turned out to be a coil pack

cdm's are a known problem with tha "electronic" motor... here is a manual for your motor.. might give ya some direction.. be patience.. it opens kinda slow sometimes..

http://boatinfo.no/lib/mercury/manuals/135-150-175-200.html#/0

I really appreciate all the input guys.

how hard is a coil pack install? expensive?

wait. i did coil packs on my ford. that was easy breezy. same type deal?

thank you TLW

ok so today before removing the coil packs I numbered each of them in accordance with the numbers on the working harnesses. I tested the impedance (ohms) from the end of spark plug wire to each pin inside the opposite side of the CDM (also known as the coil pack apparently). I found that one coil pack has drastically different impedance than the others. here we go.

COIL PACK/CDM 1
1.1
7.3
1.7
.46

Coil Pack/CDM 2
1.2
9
2.3
.6

Coil Pack/CDM 3
1.1
12.6
2.3
.69

Coil pack /CDM 4
1.1
6.4
2.3
.48

Coil pack CDM/5
1.1
10.2
2.3
4.03***

Coil Pack CDM 6
1.1
9.1
2.3
.65

So it is pretty obvious that Coil Pack CDM 5 has some drastically different impedance issues. I went ahead and ordered another coil pack off amazon ($35) instead of $96 at the mercury marine dealer i called this afternoon. They had to order it anyways.. I am hoping I have identified my problem. Once the coil pack comes in I'll post about if the boat runs any better.

Any one think I should be looking at something differently? I guess the next step for me are the voltage regulators. the problem is that i don't understand how to bench test them.

Speaking of which my tach on my dash does not work. I am going to switch the grey tach output wire tomorrow from one (only one being used now) voltage regulator to the next and see if the tach on the dash starts working. I've been told to try this. Dunno how to test anything else on the tach though.

page 2B-15 in manual.....