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9.9 or 15 carbs.. Did i get hosed????

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BRUPP79

Regular Contributor
Good afternoon gents. I am guessing I got hosed here, unless I missed something. OK, I will try to make this more clear than mud. Carb A 15hp on left side new and shiny, Carb B 9.9hp on right, old and dirty. Carb B i know is a 9.9 as it has a .8125" dia throttle bore and approx .6875 venturi dia, but came with a #51 jet. Carb B has a 1.000" throttle bore and a .6875 venturi dia, but came with #38 jet. Carb A was bought online as a 15hp and I guess I missed the venturi size in the picture. Carb B is what is on the 9.9hp engine at the moment. The engine runs fine, sorta sluggish getting to a plane with anything more than 2 people in the 12ft lund boat, but does get there, plugs tan in color. My questions are: Is Carb A really a 15hp even though the venturi isn't .875 and it came with a #38 jet? Second, should Carb B have the #38 rather than the #51 jet in it? I have been searching, and have found no answers that say Carb A is a 15hp, being it has the small venturi. And i have found mixed results as to the proper main jet size, although the majority say run the #38 jet in it. Fully confused here.
Thanks for the help.

Can't get pictures to load, will try later to edit :mad:

P.S. Carb A has large brass tube half and small brass tube fully thru the venturi, Carb B has large brass tube half way only.
 
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All my 15 hp carbs do not have the tube through the middle the 9.9 carbs do. Are you measuring in the center of the carb that is where it counts. There is a significant difference in the 2 venturis.
 
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carb A.jpgcarb aa.jpg OK these are Carb A the "15hp"


carb B.jpgcarb bb.jpg Carb B "9.9"

jets.jpg #38 on left & #51 on the right
 
UGGGGHHHHH..... Wouldn't you know it. I did one more search, and yes. It looks like I indeed was given a bunk-deal. I received a large bore 9.9 carb. I will wait for a confirm from you guys before i ask for my Peso's returned. Unless I just keep it if this was a better 9.9 carb design and the #38 jet is indeed the correct one.
 
flyingscott said:
All my 15 hp carbs do not have the tube through the middle the 9.9 carbs do. Are you measuring in the center of the carb that is where it counts. There is a significant difference in the 2 venturis.
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Yep, I measured the inner venturi bore where the brass tubes are. Measured .6875" on old and new-mail ordered one. I thought I had read on one post that OMC made a next gen carb that was for the 15hp that had a smaller venturi than the .875". But that could be the plastic top carb.....
 
Yes those are both 9.9 carbs one without the tube is newer version. Tell the seller he may refund your money. The problem with part #s on your carb is Evinrude does not seperate the 2 carbs on the parts fiche. The model # of the motor is the part #.
 
flyingscott said:
Yes those are both 9.9 carbs one without the tube is newer version. Tell the seller he may refund your money. The problem with part #s on your carb is Evinrude does not seperate the 2 carbs on the parts fiche. The model # of the motor is the part #.
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Thanks Flyingscott. I will message the guy tonight. At best i can find for my 1975 9.9 is either a #38 or #40 main jet correct? I will definately take out that #51 out of the current setup.
 
I will confirm what Mr. Scott posted. I do alot of 9.9 and 15's here. In fact I got 2 15 carbs from Joe Reeves a couple years ago. Sold a 9.9 the other day and happy the guy wanted to keep it a 9.9. He likes the economy and the way it idles and trolls. Personally I like to change the exhsust tuner when I convert, but I'm not sure how much difference it makes. Either jet should work, but it kinda depends on a couple things like boat load and perhaps even what your thermostat is providing for temp. A new thermo should run 145 to 150 if you gun it right alongside spark plugs. If it's running cooler, you can use the larger aforementioned jet. A hotter motor more effectively utilizes it's fuel. Thermostats are only 12 to 15 bucks and fit everything.
 
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Hey Tim, thanks for the second on the carb. I texted the guy tonight and he said he is going to dig into it. But yea I saw 9.9 as soon as I had time to look it over today. If I am stuck with it I may just run the carb to see if it makes a difference on top speed. Seems a big jump in jet size. Last big trip i did into Basswood lake by Ely it was really thirsty! Who knows, with this other carb and the #38 jet it might not slug out so much to get on-plane and sip instead of gulp fuel. I have a new t-stat comeing as well.
 
Here is a 1975 15 horse tuner. Putting together tomorrow. Did alot of mods on these 9.9 and 15's when 10 horse limits were applied up there. Used to take Fritz Mondale up when he was VP. Been fishing with him since 1967. Secret service wanted 15's, so I had a couple "sleeper 9.9's. He is still doing pretty fair for 92, but they won't let us up to Canada with this f...in Covid.....even though we are property owners at the Manitou and Big Canon NW. of Vermillion Bay off the Wabigoon. This would have been the last year his family would let him go.....but we can always try for next year. Jimmy Carter still doing pretty good too. I'm from Hibbing. Helped my Brother and Dad in the radio and TV business as a tradesman. Dad built the cable system in Hibbing in 1964. Brother Frank built KUSA radio in Hibbing....1988. That's Dad at the tillers of our twin 30's up on the Wabigoon....rock choked Clay/Segise Lake. In fact Mr. Mondale bought those motors with us in 1987. Built a camp with us on Big Canon L.....portage in only....from 1982 to 1986. We used to freight with an 18 foot Alumarine.....lined up across the transom 2, 15's with a 25 in the middle. Fun. Those were some damn good years. Sorry for social hour but if my mentors here learn a little about me, they might forgive my foolishness. Ha! Mr. Scott says I belong back in the 50's.....probably he's got a good point.
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BRUPP79 said:
Hey Tim, thanks for the second on the carb. I texted the guy tonight and he said he is going to dig into it. But yea I saw 9.9 as soon as I had time to look it over today. If I am stuck with it I may just run the carb to see if it makes a difference on top speed. Seems a big jump in jet size. Last big trip i did into Basswood lake by Ely it was really thirsty! Who knows, with this other carb and the #38 jet it might not slug out so much to get on-plane and sip instead of gulp fuel. I have a new t-stat comeing as well.
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Jets go with the carb not the motor. Why do you think you have the wrong jets
 
Just don't want to run a carb that flows the same, but has leaner jet in it. Equals a unhappy engine. I see depending on the serial number suffix for my engine they ran different jets. #38 = lean. #51 = rich. Tempted to graft a Tillotson HR onto it and have a easier to tune engine. Granted the linkage would be a trial. But in the end it would be much better. I just need to be sure that what came with this newer carb is correct. Why the steep change in jetting. Hate to seize it on a hunch.
 
You can modify some of these carbs to put an adjusting needle into the float bowl access port to main jet......I have done it several times over the years. They stopped allowing the operators to make these adjustments to high speed because of irresponsibility.....not only by operators, but our lawmakers. Kinda sad. See they got cars and trucks now that'll park themselves...come and pick you up. Don't know about you, but I actually LIKE to drive. Why would I want some ugly truck to come over to me when I push a button?
 
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