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nicknack2

Regular Contributor
"Hey JWB How are u???
Well af

"Hey JWB How are u???
Well after rebuilding my carbs (200 HP Johnson 90-93 model not sure what it really is) I found out that my HS jets are 62D at one point you stated that as an up grade...
1. All carbs, needed to be #67 HS jets EXCEPT--#2 Cyl Carb-it needs a 69. Since there is an inherent cooling problem w/that cylinder, more fuel/more oil.
Would having a 62D would reduce my RPM range at WOT???
Also I had a broken base gasket (the one that seals the carb in to the throttle bodies) on the bottom portside carb... would that cause lower RPM range?"
 
"any body????<[img]"http://www

"any body????
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"on yours,u would go up to 65D

"on yours,u would go up to 65D hs jets...all the way around.......the later models came w/65's,.62 is prob not affecting hs runs..just larger,is helping the eng longevity...but,jetting,for the rig,and the area u r in,is a tuning process...since u have 62 i'd put 65 all the way and try...no matter where u end up,u want a 2 size lgr jet,in #2 carb...looking at FRONT of eng,it will be top LEFT carb.a bad gasket anywhere on the intake side,could potentially,cause HS running prob,as well as LS prob...lean running,spitting back,.etc..."
 
As part of my tuning last year

As part of my tuning last year I downsize my high speed from 64d to 58d lost 800 RPM on my top end. So the answer is YES you will see a reduction in RPMs
 
"[b]"in #2 carb...looking

""in #2 carb...looking at FRONT of eng,it will be top LEFT carb."... top left carb(from the front of the engine)or top starboar carb should be # 1 cylinder right???"
 
[b]As part of my tuning last y

As part of my tuning last year I downsize my high speed from 64d to 58d lost 800 RPM on my top end. So the answer is YES you will see a reduction in RPMs why did you go down on jet sizes???
 
"I downsize thinking it was th

"I downsize thinking it was the reason for my plugs loading up, turns out it was wrong plugs gap at .40 , I re install the 64d and change the plugs from NGK's to Chamions and gapped at .35."
 
"re-jetting,is always,..the la

"re-jetting,is always,..the last straw...the engineers,altho,i would love to have 1 at my shop,fr time to time,for a lil discussion,..designed the eng,to run best,..in all circumstanes.....but when,u put hundreds,of tech's,having to rejet....u might...have a problem!"
 
"Now if I go to 65D or maybe 6

"Now if I go to 65D or maybe 67D what are the chances that my RPM will increase??? to the desired over 5000 RPM range??? as the RPMs decreased for Andrew after he re-jetted to a smaller jet number, it is just frustrating taking the motor to the shop have them put it on the dyno and telling me that is runs good and it is putting out the desired PSI on the dyno at the right RPMs (more frustrating is paying), then when I go in to the water, the motor just do not get over ~4500/~4700 RPMs… un less it has the air silencer off… at WOT (with silencer on) the motor feels like it is at ¾ of the power, but it just does not develop in to the full RPM range, too much fuel??? And not enough air??? I took the boat to the ocean over memorial weekend hoping that at see level I would notice a difference but the motor acted exactly the same, in reality it runs good but again it just do not develop full power…
Over propped??? 14 ½ X 19 for a 21’ old fiberglass Stamas and I’m guessing it weight little over 3000 Lbs, that prop should be about right…. now the placard on the boat states that max power of the motor should not exceed 280 HP, I have a 200 HP, before it had 6 cylinder twin Mercs (115HP from back in the 70’s) so that still puts me at the 70% max power allowed… guys I’m just frustrated I which there was a simple test that I could do to solve this issue…"
 
"Hang in there , its RPM we ta

"Hang in there , its RPM we talking about.
Remember is NEVER recommend to run the motor with the silencer off.
Note bigger jets may mean higher rpms but remember they can flood the engine and foul your plugs.
For ever pitch you reduce on the prop you should see around 200 RPM'S more.
Don't go changing the prop just yet hopefully the guys will add some valuable info later on.
I must point out also your timing MUST be right on if not you will lose top end RPM big time.
Confirmed your timing as step one."
 
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