Jetting for Evinrude 300XP

[charlie_kula]

Hello,<br /><br />Anyone knows what differs in jetting between the Evinrude 275 and the 300 xp year 88?<br /><br />The engine smokes a lot at low rpm, so my mechanic suggest re-jetting my 300xp to the jets of the 275 for the low and middle rpm. He is however unsure if it will work.<br /><br />Anyone done something similar? <br />Thanks!

 

[P.V.]

Re: Jetting for Evinrude 300XP

"Smoking" of your engine really has nuthing to do with "jetting"!!!! I would be more concern'd with engine temp and the proper oil ratio via the VRO pump! Also, consider the re-circ valves! It is NOT "normal" to change far, if at all, from "stock" jetting unless you are at altitude or are modifing performance!! Has your "mechanic" ever been around OMC looper engines at all????

 

[Dhadley]

Re: Jetting for Evinrude 300XP

I agree with P.V. Loopers are great motors but V8's are in a world all their own. Theres a lot more to it than just jetting.<br /><br />He's unsure if it will work. Is he willing to pay for a powerhead if it doesnt?<br /><br />Find another "mechanic".

 

[charlie_kula]

Re: Jetting for Evinrude 300XP

He is certified OMC and Mercury since early 80th!<br /><br />The VRO pumps are the latest updated ones. The engine runs really great when warm, but att start up it chokes out all excessive oil from the last session. I looks like indian signals! Not very popular at the yacht club <br /><br />There are feedback lines from the crank case to the manifold. The inside of the air intake cover is solked with fuel.<br /><br />Please tell me more about the re-circ valves. How do they work?

 

[seahorse5]

Re: Jetting for Evinrude 300XP

Both the 300 and 275 used the same idle air bleed jets that year. If you changed the midrange air bleed to one from the 275, the 300 motor would run richer!<br /><br />After the engine has been run and then sat overnite, remove each of the VRO fuel inlet lines and see if the gas is discolored from oil leakage internally from that pump. Sometmes a pump will have a leaking or weak outlet check valve that will allow oil to migrate into the fuel chamber when not running.

 

[charlie_kula]

Re: Jetting for Evinrude 300XP

OK, thanks for the tips!