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I just purchased a 13’ Boston Whaler with a 40HP Johnson VRO engine on it. The boat starts and runs but stalls out when I push the idle control lever all the way down. I am having trouble determining what year the engine is. Any help determining what year the engine is as well as a starting point to trouble shoot the issue would be appreciated. To start I plan on replacing the plugs as well as get fresh fuel / oil in the tank.

The following info was taken from the Engine ID Plate:
MOD No. J40ECUD
SER No. G 7417642

Thanks,
Josh

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J= Johnson
40 = HP
E = Electric
CU = the last two digits of the year using this code (INTRODUCES)
C = 8
U = 7

So you have a 1987 40HP Johnson

Now, what year is your 13' Whaler?
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Welcome aboard Whaler Central.

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Thanks for the quick response. Now its time to try and get this thing running.

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Are you running on both cyls? Have you done a compression test? If both are good, it is most likely your idle circuits. These engines have a small jet that feeds fuel for it to idle. Carbs will have to be cleaned. Easy job with torch files and some cleaner.

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So I rebuilt both carbs, changed fuel tank, fuel lines and fuel filter as well as replaced spark plugs. I thought that did the trick because the boat was running great. Put about 5 gallons of fuel thru it and it’s back to running rough. The boat ran great in a 10 minute ride to go clamming and after it sat for about an hour we were headed back it and it was running rough only on one cylinder. You could feel the 2nd cylinder kicking in for a second or two at first and now it is totally dead. Anything else I should check? Possibly a new ignition?

Thanks,
Josh

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Switch the coils and see if the dead cyl changes. My bet is on a bad coil.