95 johnson oceanrunner

Joined
Aug 27, 2008
Messages
58
just had motor rebuilt.Ran great for first few trips but now motor will surge at planing speeds.I checked fuelines from tank to motor no air leaks.Ocasionaly it wont do it.Could it just be a bad plug.
 

mikesea

Lieutenant Commander
Joined
Oct 1, 2006
Messages
1,830
Re: 95 johnson oceanrunner

when it surges does the tach drop to the same rpm,for ex.if running at 4000 and it drops to 3400,then kicks back to 4000,that would likely indicate a cyl.drop,if thats the case check all connections at coils,including the small primary wires,check the grounds to coils also,you could have loose primary or larger sparkplug wires,they should have put new plugs after rebuild,but during breakin extra oil could have fgouled,that said,you may have an issue with fuel system,but you would have an alarm if the vro system is being used and everthing hooked like factory,did you squeeze the ball during the surge,doing so will send a large flow and the surge will stop,does the ball collapse,if so prob is upstream toward tank you need to be sure your vent is working ok,a simple loosening of fuel cap thus venting that way will correct,then change or clean vent,you could have hose kinked in fuel delivery,anti siphon at tank,if you have access,do a spark and compression ,however the symptom being occasional may not show much,did the eng blow up,did they figure out why ,you may have the same problem,being fuel starved,are filters cleanlet us know what you find
 
Joined
Aug 27, 2008
Messages
58
Re: 95 johnson oceanrunner

my boat was allready in the water and i had some sparkplugs i,d bought for a johnson 115 4 of them so i went to change them even though i only had 4.The top 2 plugs were jet black and the middle ones were a little better and the bottom ones were even better.The plugs were not the same number but were the same length.Boat ran great.I,ve been mixing my fuel a little rich maybe too rich,would that do it?
 
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