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90hp johnson over oiling


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i have a 2004 90hp johnson with the oms still connected and runing xd50

i noticed a thick black burnt oil running from th ejoin between the leg and the gear case.

this hasnt happened before even though the engine gets a 5-10min run every weekend.

the difference was i havnt used the boat for 2 months or so and figured it was unspent oil

i took it out Saturday with a mix of high speed and downrigging and the smoke just wouldnt clear up to what i was use to

on the xd50 there was bugger all smoke compared to the yama lube i was using.

not very scientific measurements but basically before i could start it and not worry about where the smoke at all

i tried the texter mark on the oil res but it uses bugger all and is impossible to accurately measure

possible oms pump failure and over fueling ? air leak in fuel line causing pump to pump more ?


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They only over oil due to air on the fuel side making the fuel mixture aerated on the fuel side of the OMS and as a result the oil/fuel ratio is greater. Make sure all the fuel lines, connectors and fittings are tight and also an engine running cold will exhibit this sort of thing, so check the thermos too.

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thanks huey, it will you it will be brought to i just wanted to check it wasnt something stupidly easy to look at first

the tell tale runs hot after a few minutes

i switched to the xd50 after talking to you and the smoke was almost non existent and the prop was a grey colour and not black

now i smoke the neighbours out

ive seen unburnt oil come out of props before is it normal to leak between the leg there?

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Hi Juggs, what you see is the "split line" gearcase and that is not so much unburnt oil but soot due to the rich oil mixture. The tell tale is just that and you want to make sure that both cylinder heads are coming upto temp-especially at idle-that is critical for all outboards and it is a must to run QL78YC plugs in that OIS ignition system.



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