Changing My New Jets

[TrenchFisherman]

I went to the local marina to get jets for my project. I am using my 150 hp carbs on my rebuilt 200 Hp block. He ordered me jets to make it work but i have a question on where to put them. The orifice jets are what concerns me. There use to be size 34's i believe in the orifice jet that you can see in the opening when you remove the air cleaner. I replaced them with 35's but then after looking the whole carb over i noticed that there were more orifice jets in the float bowl cover which are 29's. My question is did he not give me enough jets or am i just suppose to replace only the ones i did? I know this is confusing but I am confused myself. Thanks a lot

 

[Dhadley]

Re: Changing My New Jets

There is no need to change jets. The carbs are jetted to mix fuel with the appropriate ammount of incoming air. The carbs ahve no way of knowing if they are on a V4 or a V6. The jetting and calibration is according to venturi size not horsepower.<br /><br />Good luck!

 

[FlyBoyMark]

Re: Changing My New Jets

CORRRRECTO.....Dhadley..........

 

[TrenchFisherman]

Re: Changing My New Jets

so you are saying that even if i had a 1986 Evinrude 150hp V6 and now i have a 79 200 hp v6 and i am using the 150hp carbs the jets will be the same? how come everyone else told me to get new jets?

 

[Dhadley]

Re: Changing My New Jets

Yes. The carbs are metered to flow of air. The larger ports in the 200 will pull more air therefore more fuel. <br /><br />The 150 carbs probably have the 1 1/4 venturis. If the 150 was set up properly (capeable of 5800 with an average load) the 200 will give you a bit better acceleration and slightly better top RPM. Maybe 100 or so. <br /><br />To check for proper jetting, run the boat on plane and start at about 3500 RPM. AS you are running along hit the primer. If the RPM's pick up then fall off, its lean. If the RPM's fall off immeaditly, its slightly rich and most likely OK. If it blubbers without hitting the primer, its rich. <br /><br />Do this at 500 RPM increments until you get to 5000. Then go in 200 - 300 RPM steps. <br /><br />This is all assuming the motor is running well and broken in, with the correct plugs (Champion L or QL77JC4) the right fuel (fresh 87).<br /><br />As you have found out, carbs off the same horsepower are metered differently which effects the way they are calibrated. Some have circuits that others dont, like pull-over circuits. Some have only two jets per side. Some have 3. Some have the mid range jet inside in the bowl, some have the mid range jet accesible from the outside. <br /><br />Sorry about the long post, but its not all that simple. I wish it was.<br /><br />To answer your last question -- I don't know. Sorry.<br /><br />Good luck!

 

[TrenchFisherman]

Re: Changing My New Jets

wow...everyone has been telling me that if i don't jet up i will burn down the new powerhead i bought. even the local dealer called some reps up and they told him the jets i should order. i do believe you though because what you said makes sense. so i should go back home and put the original 150 carbs back on my 200 motor and run it? sorry i am asking the same question but i like to be told over and over again. u seem to know what you are talking about and if you want to reply to me directly you can email me at sgruver78@yahoo.com i would aprreciate it!!!

 

[Dhadley]

Re: Changing My New Jets

Its good to be cautious. If the high speed jets you bought are larger I might put them in to be on the safe side until I got the rig dialed in. The idle jets may have to be fine tuned but thats a product of todays fuel more than anything. <br /><br />Set the deal up to be capable of 5800 with an average load, use FRESH 87 octane and Champion (Q)L77JC4 plugs and it'll run great.<br /><br />Good luck!

 

[Dhadley]

Re: Changing My New Jets

One more thing -- make sure the hi speed jets are "C" type and not "D" type. They are stamped as such.<br /><br />Good luck!

 

[Dhadley]

Re: Changing My New Jets

I keep re-reading your first post. Are you saying he only sold you 6 jets (very small) to go in the roof of the carb throat? If so, those are idle air jets. If you go bigger on those you will make the motor leaner at idle because they regulate air - not fuel. <br /><br />Just asking.

 

[TrenchFisherman]

Re: Changing My New Jets

he gave me two different looking jets to replace six of each. two longer ones where i had to remove screws on the side of the float bowls which i know are right. the other "Orifice" jets according to the books are what concern me. the ones that i replaced are near the needle on top of the venturi opening because i thought they were the only ones but when i went to put the bowl back on the carb i saw that there were more orifice jets in there as well. i don't know if i changed the right ones

 

[TrenchFisherman]

Re: Changing My New Jets

^