I tried searching on Seahorse, and didn't see this addressed in the 200+ posts. 
<br /><br />I acquired a 69 Seahorse 33 over the weekend. It was running rough during test drive, so I pulled the plugs to take a look. The bottom plug was loose. Neither was *significantly* fouled, but didn't look "new" either.<br /><br />The manual suggests J4J plugs. The top cyl was running a J8J, and the bottom a J6C. Nobody in my small village (hardware store, NAPA, two marinas) was open over the weekend to get new plugs. (The hardware store was, but didn't have J4Js - not even listed in the Champion cross reference book! )<br /><br />I cleaned and replaced the plugs. About 10 minutes up the river I hit a rock and my pontoon started running rough. Touched top wire, all OK. Touched bottom wire, shocked The bottom plug had snapped in half! (Old plug? Hairline crack?)<br /><br />Limped back home, then pulled another J6C out of an old non running 'Rude in my garage. Put it in, and got running again. Trolled up, watched the sunset over the marsh (incredible ) and then back home.<br /><br />On the way home, my neighbor *blew* by me in his much newer pontoon with Merc 30. (I was half his speed!) I could pull either plug wire and keep the motor running on 1 cyl, so I know both were firing. (I believe my ponts are galv steel, while his are much lighter aluminum.)<br /><br />OK, way too much detail now My questions: what is the correct plug to take the place of those J4Js? Is the J8J hotter? Or is it just the 'intended use' of the plug that differs? (i.e. 8 = snowblower rather than 4 = marine?) What about the J6C? Is this a 'direct replacement with updated part numbers' or the previous owners have just found that J4Js weren't hot enough and this is conventional wisdom?<br /><br />While I don't LACK power, I probably should be getting more than I am. Once I'm up to speed, there shouldn't be as much difference in the two boats - just the amount of time it takes to get the extra weight up to speed. What can I do to look at this? (A new prop is likely my first order of business! Admittedly the one on there is pretty carved up.) <br /><br />One additional bit of info, I do have more than what I consider an acceptable level of oil/gas in my exhaust/cooling. (I can see it on the water when idling.) I also see it if I manually tip my outboard out of the water. (I don't have power trim.) I'm not 'dumping' gas - I've had that happen with another motor when one cyl quit working altogether - but it is more than what I think it should be. (And I don't want to pollute the river.)
<br /><br />I acquired a 69 Seahorse 33 over the weekend. It was running rough during test drive, so I pulled the plugs to take a look. The bottom plug was loose. Neither was *significantly* fouled, but didn't look "new" either.<br /><br />The manual suggests J4J plugs. The top cyl was running a J8J, and the bottom a J6C. Nobody in my small village (hardware store, NAPA, two marinas) was open over the weekend to get new plugs. (The hardware store was, but didn't have J4Js - not even listed in the Champion cross reference book! )<br /><br />I cleaned and replaced the plugs. About 10 minutes up the river I hit a rock and my pontoon started running rough. Touched top wire, all OK. Touched bottom wire, shocked The bottom plug had snapped in half! (Old plug? Hairline crack?)<br /><br />Limped back home, then pulled another J6C out of an old non running 'Rude in my garage. Put it in, and got running again. Trolled up, watched the sunset over the marsh (incredible ) and then back home.<br /><br />On the way home, my neighbor *blew* by me in his much newer pontoon with Merc 30. (I was half his speed!) I could pull either plug wire and keep the motor running on 1 cyl, so I know both were firing. (I believe my ponts are galv steel, while his are much lighter aluminum.)<br /><br />OK, way too much detail now My questions: what is the correct plug to take the place of those J4Js? Is the J8J hotter? Or is it just the 'intended use' of the plug that differs? (i.e. 8 = snowblower rather than 4 = marine?) What about the J6C? Is this a 'direct replacement with updated part numbers' or the previous owners have just found that J4Js weren't hot enough and this is conventional wisdom?<br /><br />While I don't LACK power, I probably should be getting more than I am. Once I'm up to speed, there shouldn't be as much difference in the two boats - just the amount of time it takes to get the extra weight up to speed. What can I do to look at this? (A new prop is likely my first order of business! Admittedly the one on there is pretty carved up.) <br /><br />One additional bit of info, I do have more than what I consider an acceptable level of oil/gas in my exhaust/cooling. (I can see it on the water when idling.) I also see it if I manually tip my outboard out of the water. (I don't have power trim.) I'm not 'dumping' gas - I've had that happen with another motor when one cyl quit working altogether - but it is more than what I think it should be. (And I don't want to pollute the river.)