2001 Mercury XR6 150 HP Trouble at Full Throttle and Under Load

[GWConrad86]

Hey Everyone,

New to the site, great information offered and thought this maybe a good place to ask for some advice. I own a 2001 Mercury XR6 150 HP. Great motor, have had it since March. Runs great until recently where I am confused at the problem. I am pretty familiar with boat motors, have owned three different boats, and have upgrade in horse power each time. Here is the story behind the mystery.

I fish in a bass fishing league and last Wednesday night got down poured on hard. Motor was running fine whole night, trailer it home and put the cover on it. Two days later went up north to walleye fish and put premium gas in her with a can of sea foam and dropped it in the water. Started right up, went to WOT and she was not running right. Barely got on plan and max out a 37 mph @ 4200 rpm. She usually goes 57 mph at 6300 rpm and jumps out of the water. Right there thought water in the fuel or bad gas. Motor idles just fines, start no problem, runs good till about 3000 rpm. So here is the checklist of stuff I check.

A. Took fuel out and put new fuel in, No Change.

B. Checked spark plugs and put new ones in. No Change

C. Check electrical connections for moisture build up. Everything looked good.

D. Check spark at coils and power packs. Everything was zapping good, except for the bottom left cylinder. it was not hitting as many times as the others. Switched a power pack/cable from another cylinder. Same result. Not a weak hit, but not as many times as other ones. Right there I suspect this being the issue, but do not have the tools to check at the time or maybe that is how it is timed.

F. Got home after dealing with issue for 4 days, took the carbs apart needles, jets, floats, and inspected/cleaned. They looked great. idles even better now. No change though.

G. Checked Fuel pump for leak at diaphragm, looks good, fuel filter clean, that's good. primer bulb is good and hardens when squeezed.

H. Looks for blown fuses inside motor housing, they are good. No cracks in wires or condensation on connectors from what I saw.

I am pretty handy with outboard motors and I am scratching my head at this point. It is really frustrating me. How does a motor start good, idle good, but run at 3/4 its power without fuel supply issues? I think it is electrical at this point but do not know where to start. Battery is new, connections are good. could the moisture from the down pour cause this issue suddenly. It was like a light switch.

Any Ideas? Thanks in advance

 

[Dukedog]

probably one of three things.. cdm, control module or stator (possible but unlikely).. didn't really understand what you swapped to test.. swap complete cdm/plug wire with one thats known good.. if low and/or bad spark follows, cdm is bad.. if not then more than likely control module.. send me an email addy and i'll send ya a coupla oem manuals

jus because, check and clean ALL grounds small and large............

 

[GWConrad86]

Thanks for the response. I was thinking the same thing, has to be electrical at this point. I swapped one of the spark plug wire packs with one of the other ones that I knew was working properly. It worked the same as the bad one did. Showed spark but not hitting as many times as the other 5 cylinders. It would only spark 1 time compared to the others hitting 3 times in the same amount of time. That probably is the cause of lack of power since that cylinder is not firing as many times as the others. Not sure if it is timed that way until it reaches a certain RPM. I will clean all of the grounds. It was weird how it just stop working right like a light switch, but runs great at lower RPM

Not sure how to send a email addy since I am new to the site.

 

[Dukedog]

may be tha stator..hard ta tell ona computer... manual will tell how ta test 'lectronics and what ya need ta test with....

click on "Dukedog".. will open my home page.. click on message.

 

[CharlieB]

The cdm of the misfiring cyl is working. Swapping with another cdm does the same thing then it is not THAT cdm. It is the 'sister' cdm on the other side has a bad blocking diode cause the misfire on the other cdm/cyl.

This is a difficult one to prove, but you are going to have to buy one new cdm. Generally I always telll everyone NEVER buy any electrical parts until you have proven the fault as there is NO RETURN. This is the one exception to that rule.

Once you get the new cdm replace one cdm at a time and retest the spark in the 'missing' cyl. Rotate your new cdm to each cdm position. Once you try it in the correct one the missing cyl will be magically cured.

Most likely it is the cyl immediately before in the firing order of cyls.

 

[GWConrad86]

Thanks for the information, I will be definitely trying your suggestions when I get the boat back from the marine I sent it too. I am on a tight schedule with vacation coming next week and it is my best chance at landing a big musky this season. Caught a 40 and a 45 last year up there.

I did a lot of reading in the Seloc manual I just bought for the motor. It is suggesting exactly what you are saying and also that my rectifier/regular may be going bad. I did notice my mph tach was not working properly when I last tested the motor and it was fluxing up and down then returned to normal again. I believe that the voltage is not getting to the CDM of one of the cylinders under heavy load. I need to borrow my fathers multi meter and do some leg work on the rectifier. I read in the manual that you can disconnect it and see if the misfiring disappears. When I rev the motor it has a deep growl instead of the nice clean high rev sound at WOT. But idles like a champ and starts beautifully. I think the component is just starting to crap out and I caught it at the very beginning of the problem.

What cracks me up is I send it into the marine and they are stumped. So they called me to go over the issues with there tech guy and I had better suggestions what to do then they did. They put it on the dyno and said it got 5500 RPM on the dyno. But they put it on the water and only got 40 mph out of her and think it is because the prop pitch. I was like "No man, It is not functioning right, it goes 56 mph not problem when running properly and he didn't believe me. So I am temped to go pick my boat up and do it myself.

 

[GWConrad86]

The mechanic got back to me yesterday and said the Trigger had cracks in it causing two cylinders to lose spark under load. So we are putting a new trigger in to see if it fixes the issue. Mercury said that we should switch out the Control Module also but I do not think that is necessary and that module cost a arm and a leg.

 

[78dave]

did that fix it