1990 SN Spark Plug Problem

[rkuntze]

My 351 240hp SN is only getting 4000rpms after a carb rebuild and new spark plugs. Before the rebuild i was getting 4500rpms. I checked the plugs and all of them look like new except 2 of them are very very black. The low volts light on the dash also comes on ever once and awhile. When going full throttle from a dead stop it will pull pretty decend but then only go to about 37mph or 3800-4000rpms. The boat idles and otherwise runs fine. It smells like it is not burning some fuel tho when wakeboarding behind it??? Anyone have any ideas. Thanks

[Rick]

RE: 1990 SN Spark Plug Problem

It sounds like a cracked cap or loose wires. For the price I would replace the wires and make sure all plugs are firing. I would also check the firiing order It's possibler the wires were put back in the wrong order. The 2 black plugs aren't firing or firing occasionally.

[DavidF]

RE: 1990 SN Spark Plug Problem

Also, check the float level for the secondaries. The float may be adjusted too low and starving the secondaries of fuel at WOT. This will cause a lean condition that can damage the engine at WOT.

[rkuntze]

RE: 1990 SN Spark Plug Problem

I looked in the carb while someone was driving wide open throttle and the secondaries were only 1/4 open, but there was alot of fuel coming out of the secondaries. It just isnt burning it up fast enough, hence why i think i have 2 really dark plugs and one wet plug. Im thinking it must have something to do with the plugs and or the cap, points, or wires. Let me know if u guys think im on the right trail. Thanks

[DavidF]

RE: 1990 SN Spark Plug Problem

I still think it is a carb setup issue since you had it rebuilt. Standard float settings are not correct with the carb at the angle present in DD boats. Unless you have a newer boat with the PCM reduction tranny that lets the engine sit more level in the boat.

You may be flooding the secondaries.

[rkuntze]

RE: 1990 SN Spark Plug Problem

well it was a couple faulty plug wires and spark plugs were junk right out of the box. New wires and plugs and she snorts fire once again!

[rkuntze]

RE: 1990 SN Spark Plug Problem

what way should the secondary float be adjusted if it is flooding out? Should i bend the tab down which raises the float up so that it is no longer paralell with the floor of the bowl? This would have the float going uphill so to speak...is that right? Let me know...thanks

[rkuntze]

RE: 1990 SN Spark Plug Problem

also i noted while rebuilding my carb that the original seat # was 97 and the one that came in the kit was something like #115. Dont know if that makes a difference or not. The needles were the same part #

[83sn2001]

RE: 1990 SN Spark Plug Problem

well it was a couple faulty plug wires and spark plugs were junk right out of the box. New wires and plugs and she snorts fire once again!

If your adjusting the float for a flooding condition you want to lower the float. Asfar as your needle and seats go if they didn't mtch you would really be experiencing some flooding.If the above post is correct I would leave it alone.

[rkuntze]

RE: 1990 SN Spark Plug Problem

no the dealer told me it was running great, and when i got it back same thing 4000 rpm tops. So i checked their new plugs and 4 of them were black. The new rebuild kit from skidim had a different seat # in it, im wondering if this is causing my rich condition on the topend? It may also be affecting my float position. ??????