'84 - 150HP Mercury If It's Not Plug Wires, What?

[PaulDskier]

My 150HP Mercury was rebuilt 2 years ago. It has maybe 10 hours use since the rebuild. Toward the end of last year the boat would not plane out as the motor would sputter and spit for several minutes after being cranked(maybe 15 minutes). <br />It seemed that once the motor became hot it would run fine the rest of the day. I checked the plug wires last night and got good fire from only three of the wires. All the wires are new from the rebuild. If the wires are good, what could be the problem?<br />May sound like a dumb question, but this is my first outboard. Any help would be appreciated. pauldskier@aol.com

 

[Yepblaze]

Re: '84 - 150HP Mercury If It's Not Plug Wires, What?

You will need to do some diagnostic work.<br /><br />"Toward the end of last year the boat would not plane out as the motor would sputter and spit for several minutes after being cranked(maybe 15 minutes)."<br /><br />Lets get on the same track with the terms. Cranked usually will mean "with starter motor"<br /><br />Run would indicate the motor was run or running.<br /><br />So lets assume you are indicating that after running the motor for what at times might have been 15 minutes it has a loss of power and performs poorly.<br /><br /> Check the compression in all the cylinders. They need to be within 15% of each other. <br /><br />Perhaps it's time to dissasemble and clean out the internal components of the carbs.

 

[sho305]

Re: '84 - 150HP Mercury If It's Not Plug Wires, What?

A known problem with these Mercs with the dual ignition boxes (if you have them) is one will go bad. Then 3 good sparks and 3 bad. You can switch them and see if the other 3 cylinders have bad spark then. You can trace the wires to which box they are. <br /><br />Could also check the plugs to see what ones are running poorly anyway, and do above post(and always use new plugs first on a 2-stroke).<br /><br />Hope this helps, and yes the CDI boxes are pricey but seem to last a while. There are aftermatket ones available now I have heard.

 

[PaulDskier]

Re: '84 - 150HP Mercury If It's Not Plug Wires, What?

I finally have had some time to do some more checking.<br /><br />I switched one of the plugwires I knew was good with one of the ones that was not getting fire. And still no fire. I also did the same with the Spark Plugs. Same result, no fire. I'm going to try to switch the power packs as suggested and see what happens. <br /><br />I will also buy a compression gauge and see what I get there and let you know what I get. <br /><br />Sorry I took so long..<br /><br />Paul

 

[PaulDskier]

Re: '84 - 150HP Mercury If It's Not Plug Wires, What?

Okay guys, I finally got ahold of a compression gauge. Every cylinder read 110 pounds.<br /><br />I also re-checked fire through plug wires.. Only getting fire through cylinders 1 & 2. So, what do I do now? Any help is greatly appreciated.<br /><br />Paul

 

[oldboatsal]

Re: '84 - 150HP Mercury If It's Not Plug Wires, What?

Some engines only fire on a few cylinders until a boost in RPMs is achieved. Give it some throttle and then see how many are firing.

 

[lakensea]

Re: '84 - 150HP Mercury If It's Not Plug Wires, What?

It appears you have an ignition problem. The only way to check it properly is with a peak reading voltage meter. A qualified Merc tech can check out the entire system (switch box's, charge stator, trigger & stop switch circut) in about 5 minutes. Otherwise you may be buying expensive electronic parts that you may not need. By the way, do not crank the engine over without a spark checker hooked up. If the spark has no place to go, it can damage the switch box ($180 ea).

 

[jphotroder]

Re: '84 - 150HP Mercury If It's Not Plug Wires, What?

if when cold it runs poor let it warm up before galding it it might just be the gas to air is to lean in you post you said it ran fine after running a while try a manual choke and adjust it till warm up

 

[PaulDskier]

Re: '84 - 150HP Mercury If It's Not Plug Wires, What?

OLDBOATSAL HIT THE NAIL ON THE HEAD!!<br /><br />After checking the coils, stator, trigger,plugs, wires, and all checking out fine, I gave up and took the boat to a Mercury Certified Master Mechanic. This guy really knows his stuff. He was very professional and was able to diagnose my problem in about 5 minutes. And the problem was?<br /><br />"Gummed up carburetors." WHY? Letting the boat sit over the winter without running and proper winterization the last 2 years. He proceeded to tell me that he could rebuild and clean my carbs, or buy a bottle of this stuff called "Quickleen" by Mercury ($9.95 / pint). Add 4 ounces to each fuel tank. Let the motor Idle for 45 minutes in the lake, or with the muffs on, and that it would clean my carbs as good as rebuilding them.<br /><br />I asked him about the firing on only 2 cylinders. He said the only true check of spark needed to be done with the motor cranked and turning a minimum of 500RPM.<br /><br />I'm happy to report that after the 45 minutes of idling with the quickleen, the motor ran smooth and fast the rest of the evening.<br /><br />Thanks everyone for your help.