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502 Mag plug reading
32 Sunsation Dominator, twin 502 Mag MPIs.
Ran it today for basically the first time, started and idled great, good power, but kind of fell flat after 42-4300 rpm. Saw 72mph and then nothing more. Could not gain RPM on either motor past that point. Got home and pulled the plugs out, most of them look lean to me, but I'd welcome additional opinions. I've suspected the fuel pressure is low on both motors, despite new pump on Stbd motor, possibly bad regulators on both (?) motors since pinching the return lines results in a spike to 60+ but normally they are running at barely 32psi with the vacuum lines removed from the regulators. Fuel filter/water separators are both new. I'm going to compression test tomorrow, and I'm probably going to order 2 new regulators and send out the injectors for cleaning/flow testing unless someone else has a better idea. Opinions on these plugs? Thanks! https://cimg7.ibsrv.net/gimg/www.off...07941a6f02.jpg https://cimg8.ibsrv.net/gimg/www.off...708e28b719.jpg https://cimg9.ibsrv.net/gimg/www.off...804e1aa0e5.jpg https://cimg0.ibsrv.net/gimg/www.off...2d8d861135.jpg |
X2 on the compression test then get back and repost. You might have a few down but unless you do a proper plug check it doesn’t really tell you much. You under propped?
And X2 on the injectors also! |
Curiosity kept me from waiting til tomorrow. Here's the comp test results:
Port 1 160 2 171 3 161 4 175 5 166 6 171 7 161 8 179 Stbd 1 175 2 175 3 179 4 180 5 159 6 165 7 166 8 172 |
Your fine there.
i figured you’d ck sooner. 👍 |
Are these vst or cool fuel engines ?
How old are those plugs ? Some look old and some oil fouled. Getting the injectors gone thru is smart. They weren’t the most dependable. Arcticfriends/smitty knows these intimately. Is this a new running condition or is boat new to you ? If new to you, there where a ton of these boats with these engines do i’d see what props you have snd what owners of these boats found where best props. |
On the upper set of eight plugs, #5 and #6 are heavily fouled with Ash. 8 is wet.
On the lower set of eight, #1 has ash building up. In any case new spark plugs in both engines will probably fix you right up. Temporarily. My plug insulators were white like yours. Living in Florida I dropped the heat range. Now they have a Florida tan. |
Originally Posted by SB
(Post 4826584)
Are these vst or cool fuel engines ?
How old are those plugs ? Some look old and some oil fouled. Getting the injectors gone thru is smart. They weren’t the most dependable. Arcticfriends/smitty knows these intimately. Is this a new rubbing condition or is boat new to you ? If new to you, there where a ton of these boats with these engines do i’d see what props you have snd what owners of these boats found where best props. These engines have the older injectors and the MEFI 1 style ECMs, but the later cool fuel modules (no VST). I know that stock, Sunsation determined that Bravo 1 4-blade 28P were the best prop, but this boat has 4- blade Hydromotive 28Ps on it. |
Originally Posted by AmiableDave
(Post 4826585)
On the upper set of eight plugs, #5 and #6 are heavily fouled with Ash. 8 is wet.
On the lower set of eight, #1 has ash building up. In any case new spark plugs in both engines will probably fix you right up. Temporarily. My plug insulators were white like yours. Living in Florida I dropped the heat range. Now they have a Florida tan. |
Doc, If you need any help, please let me know.
Tx, SD |
Take a look at inside of dist cap for fuzzy posts too.
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