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Author Topic:   OMC V6 Spark Plug Gap

jimh posted 09-10-2007 08:49 AM ET (US)
One of the fun parts of going boating with ol' kingfish is he has the same outboard motor as mine, a c.1992 Evinrude 225-HP V6. After a short run on John's boat I noticed his engine seemed to have smoother acceleration than mine. I was getting a bit of hesitation and stutter around 2,000 to 3,000-RPM as I accelerated. John remarked, "Mine was doing that, too, until I put in new spark plugs last week."
Ahah! I had not changed spark plugs this season, and the last time I checked the plug gap was back in October 2006. The recommended gap is 0.030-inch. So this weekend I pulled the plugs to see what they looked like. All the plugs had eroded the center electrode to the point where the gap was over 0.040-inch, and several were even more worn. I had a new set of plugs ready to go, but I decided to save them for 2007, so I just reset the gap on the old plugs.
Yesterday I had the boat at the local lake for some propeller testing and guess what: no more stutter or hesitation in the range of 2,000 to 3,000-RPM when accelerating. The spark plug gap was all that was wrong. And it is an easy cure to implement.
As a result of modern automobile ignition systems and their iridium or platinum tipped plugs which can last for 100,000-miles, I had forgotten that the capacitor discharge ignition on my old outboard was zapping these plugs rather hard. Electrode wear looks like it can take them out of tolerance in about 50-hours of use. Note to self: check those plugs mid-season and re-gap them.
cdnwhaler posted 09-10-2007 09:34 AM ET (US)

I had very similar experience on my 1990 V6 225 Evinrude with that very same fellow this summer . Luckily I had a complete set of new plugs with me which he promptly changed... I had the plugs he had the wrench... one more item I neglected to carry, along his recommendation of a better gap tool. Mine were worn to .04+ like yours.
What turned up as well was a fouled plug wire. So check the wires too for possible replacement. And check both ends. Mine was fouled on the coil end, not the plug end.
Pete
newt posted 09-10-2007 09:48 AM ET (US)
Jimh, Based on a few of your posts, I may try and switch to the XD-50 oil that you run. I use XD-30, and find that I need to remove and clean (or simply replace) the spark plugs long before they wear down that much. I can tell the plugs are getting fouled up from the way the engine idles and typically the gap has only eroded to .035" +/-.
I assume that since you only re-gapped, that the plugs still looked nice and clean?
Peter posted 09-10-2007 01:30 PM ET (US)
It's not just the gap between the hook and the center electrode that needs to be right. For a J-shaped spark plug to work properly, the center electrode also needs to have a "corner". Electricity tends to concentrate at corners and a rounded off electrode doesn't have corners for the electrical energy to concentrate. So even if the gap is good, if the center electrode does have that "corner" edge coming from a cylindrical shape, it might not be working as well as it could.
jechura posted 09-10-2007 10:50 PM ET (US)
At least you guys with those modern V6 Outboards have plugs to gap! I can't do anything with the Surface gap plugs on my old 1985, but clean or replace.
Jerry
jimh posted 09-11-2007 02:26 AM ET (US)
Peter--your insight is excellent because the center electrode of these plugs was worn away and rounded. When I pull them out next spring I will try to remember to take a picture of them. The motor will only be run a few more hours this season and then heavily fogged, so I couldn't bring myself to install new plugs now.
The plugs were a bit on the oily side. The only time I have seen the elusive dry and light brown color on my plugs was when I pulled them right after a long high-speed run followed by almost no idle time. Any time at idle and they seem to get dark and oily.
knothead posted 09-11-2007 12:42 PM ET (US)
My plugs always seem a little oily as well. I don't believe I've ever pulled a plug that was a light tan color and dry. It must be an OMC thing.
Just guessing
regards---knothead
DeeVee posted 09-11-2007 09:31 PM ET (US)
Jim,
Almost the exact story with my 1992 Suzuki 200. I changed the plugs and she purrs again.
I also note that my plugs always seem oily. I have never seen them the preferred dry, chocolate color.
I just change the plugs often, especially since NAPA stocks the NGK plugs. It only costs $13.00 to replace the set. Double that if I buy plugs from the local Suzuki dealer.
Doug
jeffs22outrage posted 09-11-2007 09:54 PM ET (US)
I am with Jerry however, I prefer the surface gap plugs. I have and still run NGK surface gap plugs in ALL of our Outboards and other 2 stroke motors. I ran the standard gap champion plugs in 235 Evinrude when I first bought the boat as they were brand new. With in 2 outings they seemed to have lost smoothness and power. I replaced them with NGK's and have been happy ever since. I also like them because there is no gap to set so no need for a gap tool. It can be a pain gapping the plugs when on the water rolling around. Makes it though to hit the hole the first time and even the slightest tap of the prong can change the gap. Get the tool out and repeat said process.
Of course Dave and Doug at lockeman's give me hell every time they see those plugs but, mainly the flack is that they are Japanese plugs not US made. Doug did tell me last time I was in that the motor will not be affected by running the surface gap plugs.
To each their own but, I say to try them next time you by a set of plugs.
Sal DiMercurio posted 09-11-2007 11:59 PM ET (US)
If you are just cleaning your plugs with a wire brush, & starting fluid, & re-gaping them at .030, you also need to use a diamond finger nail file, to square off the end of that electrode & under the electrode, just as Peter said.
I thought everyone knew that.
While speaking of using the Bombardier XD50 oil, I premix mine on my 1997 - rebuilt 70 hp at about 60.1 ratio, as I troll for hours on end & hardly ever go to wot.
This engine while using the XD50 oil, just plain purrs at idle for sometimes 3 hours straight & not even a hint of smoke, & absolutely no hesitation, or stumbling, when going from a 3 hour troll to 3500 rpms where I cruise.
Today was exceptional rough on the water, on the Sacramento river, with the outgoing tide [ current ] running to the Southwest at 4 - 5 mph, & the 25 - 30 mph Southwest wind, blowing to the North east,[ against the flow of the water ] making for 5' - 6' & breaking.
We were in my 15' sport & he said, were gonna get soaked,................to his surprise, not even 1 single drop of water in the boat, or on us, & never came off plane, while running in the trough & quartering the waves.
Trolled for 2 hours, limited on stripers from 12 lbs to 16 lbs, & back across the open water again [ 4 miles of open water ], & he kept saying, this little boat is amazing, I can't believe how this little boat handles this lousy water.
Back to plugs, try Napa auto parts for the best price in plugs.
Sal

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Author	Topic: OMC V6 Spark Plug Gap
jimh	posted 09-10-2007 08:49 AM ET (US) One of the fun parts of going boating with ol' kingfish is he has the same outboard motor as mine, a c.1992 Evinrude 225-HP V6. After a short run on John's boat I noticed his engine seemed to have smoother acceleration than mine. I was getting a bit of hesitation and stutter around 2,000 to 3,000-RPM as I accelerated. John remarked, "Mine was doing that, too, until I put in new spark plugs last week." Ahah! I had not changed spark plugs this season, and the last time I checked the plug gap was back in October 2006. The recommended gap is 0.030-inch. So this weekend I pulled the plugs to see what they looked like. All the plugs had eroded the center electrode to the point where the gap was over 0.040-inch, and several were even more worn. I had a new set of plugs ready to go, but I decided to save them for 2007, so I just reset the gap on the old plugs. Yesterday I had the boat at the local lake for some propeller testing and guess what: no more stutter or hesitation in the range of 2,000 to 3,000-RPM when accelerating. The spark plug gap was all that was wrong. And it is an easy cure to implement. As a result of modern automobile ignition systems and their iridium or platinum tipped plugs which can last for 100,000-miles, I had forgotten that the capacitor discharge ignition on my old outboard was zapping these plugs rather hard. Electrode wear looks like it can take them out of tolerance in about 50-hours of use. Note to self: check those plugs mid-season and re-gap them.
cdnwhaler	posted 09-10-2007 09:34 AM ET (US) I had very similar experience on my 1990 V6 225 Evinrude with that very same fellow this summer . Luckily I had a complete set of new plugs with me which he promptly changed... I had the plugs he had the wrench... one more item I neglected to carry, along his recommendation of a better gap tool. Mine were worn to .04+ like yours. What turned up as well was a fouled plug wire. So check the wires too for possible replacement. And check both ends. Mine was fouled on the coil end, not the plug end. Pete
newt	posted 09-10-2007 09:48 AM ET (US) Jimh, Based on a few of your posts, I may try and switch to the XD-50 oil that you run. I use XD-30, and find that I need to remove and clean (or simply replace) the spark plugs long before they wear down that much. I can tell the plugs are getting fouled up from the way the engine idles and typically the gap has only eroded to .035" +/-. I assume that since you only re-gapped, that the plugs still looked nice and clean?
Peter	posted 09-10-2007 01:30 PM ET (US) It's not just the gap between the hook and the center electrode that needs to be right. For a J-shaped spark plug to work properly, the center electrode also needs to have a "corner". Electricity tends to concentrate at corners and a rounded off electrode doesn't have corners for the electrical energy to concentrate. So even if the gap is good, if the center electrode does have that "corner" edge coming from a cylindrical shape, it might not be working as well as it could.
jechura	posted 09-10-2007 10:50 PM ET (US) At least you guys with those modern V6 Outboards have plugs to gap! I can't do anything with the Surface gap plugs on my old 1985, but clean or replace. Jerry
jimh	posted 09-11-2007 02:26 AM ET (US) Peter--your insight is excellent because the center electrode of these plugs was worn away and rounded. When I pull them out next spring I will try to remember to take a picture of them. The motor will only be run a few more hours this season and then heavily fogged, so I couldn't bring myself to install new plugs now. The plugs were a bit on the oily side. The only time I have seen the elusive dry and light brown color on my plugs was when I pulled them right after a long high-speed run followed by almost no idle time. Any time at idle and they seem to get dark and oily.
knothead	posted 09-11-2007 12:42 PM ET (US) My plugs always seem a little oily as well. I don't believe I've ever pulled a plug that was a light tan color and dry. It must be an OMC thing. Just guessing regards---knothead
DeeVee	posted 09-11-2007 09:31 PM ET (US) Jim, Almost the exact story with my 1992 Suzuki 200. I changed the plugs and she purrs again. I also note that my plugs always seem oily. I have never seen them the preferred dry, chocolate color. I just change the plugs often, especially since NAPA stocks the NGK plugs. It only costs $13.00 to replace the set. Double that if I buy plugs from the local Suzuki dealer. Doug
jeffs22outrage	posted 09-11-2007 09:54 PM ET (US) I am with Jerry however, I prefer the surface gap plugs. I have and still run NGK surface gap plugs in ALL of our Outboards and other 2 stroke motors. I ran the standard gap champion plugs in 235 Evinrude when I first bought the boat as they were brand new. With in 2 outings they seemed to have lost smoothness and power. I replaced them with NGK's and have been happy ever since. I also like them because there is no gap to set so no need for a gap tool. It can be a pain gapping the plugs when on the water rolling around. Makes it though to hit the hole the first time and even the slightest tap of the prong can change the gap. Get the tool out and repeat said process. Of course Dave and Doug at lockeman's give me hell every time they see those plugs but, mainly the flack is that they are Japanese plugs not US made. Doug did tell me last time I was in that the motor will not be affected by running the surface gap plugs. To each their own but, I say to try them next time you by a set of plugs.
Sal DiMercurio	posted 09-11-2007 11:59 PM ET (US) If you are just cleaning your plugs with a wire brush, & starting fluid, & re-gaping them at .030, you also need to use a diamond finger nail file, to square off the end of that electrode & under the electrode, just as Peter said. I thought everyone knew that. While speaking of using the Bombardier XD50 oil, I premix mine on my 1997 - rebuilt 70 hp at about 60.1 ratio, as I troll for hours on end & hardly ever go to wot. This engine while using the XD50 oil, just plain purrs at idle for sometimes 3 hours straight & not even a hint of smoke, & absolutely no hesitation, or stumbling, when going from a 3 hour troll to 3500 rpms where I cruise. Today was exceptional rough on the water, on the Sacramento river, with the outgoing tide [ current ] running to the Southwest at 4 - 5 mph, & the 25 - 30 mph Southwest wind, blowing to the North east,[ against the flow of the water ] making for 5' - 6' & breaking. We were in my 15' sport & he said, were gonna get soaked,................to his surprise, not even 1 single drop of water in the boat, or on us, & never came off plane, while running in the trough & quartering the waves. Trolled for 2 hours, limited on stripers from 12 lbs to 16 lbs, & back across the open water again [ 4 miles of open water ], & he kept saying, this little boat is amazing, I can't believe how this little boat handles this lousy water. Back to plugs, try Napa auto parts for the best price in plugs. Sal