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Mid 70s three cylinder Johnson carb fuel efficiency upgrades?

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Buckey

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It might be a bit early for me to be asking this question as I haven't operated this boat/motor combo yet.
I recently bought a 1973 Johnson 65 that I am familiar with, as it had been serviced for years by someone I know. I will be installing it on an early 80s Vanguard Banshee. I'm told that these motors are quite hard on fuel as the carbs don't have any fuel metering abilities. I understand that these three cylinder motors have been used for several years. Can anyone tell me if the later model carbs on these motor are any better in terms of fuel metering/efficiency? If so, has anyone tried to upgrade to new model carbs?
Thanks
 
Fuel consumption is not really determined by the carburetors.-----Yes go ahead and try a set from a 1988 model 3 cylinder.---From a 49 cubic inch model as there are also 56 cubic inch motors in later years.
 
faztbullet said:
You will need to rejet if using the 56ci carbs on a 49ci...been there and done that.
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Thanks, do you know if the newer carbs have a better fuel metering system when compared to the older ones?
I have the 73 model. If not I probably won't bother spending the time.
 
I have another post out there for this question, but I thought I'd ask here as well (no hits on the other post).
I see that the bottom of my boat near the back appears to have indentations on each side, but not in the middle.
If I lay a straight edge where I've displayed the green marking I see a gap, around 1/4inch at its deepest point.
Would this be design from the manufacturer or would it be that the back of the boat is flexing downward.
It is odd that the center is not like that though?? Any insight would be appreciated. Thanks.
 

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The hull could be MFG idea to add air into water steam tp loosen up hull or a molding/layup problem(my bet).....The carbs wont make any difference except a little mid-range grunt. Going to burn 7 gallon of fuel @WOT no matter if 1974 or 1994
 
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Buckey... Take "Bullets" advice, leave the time tested original carburetors alone as contrary to your belief pertaining to fuel metering abilities, they do incorporate the same type brass high speed and idle metering jets..... and you aren't going to get any better than what the engineers have com up with.

At full throttle, yeah, that thing will run through six gallons of gas pretty quick, however after hitting full throttle and being on a plane... then dropping back to approximately 3/4 throttle will put the engine into what is referred to as cruising range whereas that six gallons of fuel fuel will last roughly another 45 minutes. That action leaves the spark advance at its full setting BUT drops the carburetor throttle butterfly setting considerably without too much a loss of speed.

Remove the hood and run through that scenario with the engine NOT running while observing the engine's linkage movement to see what I speak of.
 
joereeves said:
Buckey... Take "Bullets" advice, leave the time tested original carburetors alone as contrary to your belief pertaining to fuel metering abilities, they do incorporate the same type brass high speed and idle metering jets..... and you aren't going to get any better than what the engineers have com up with.
Click to expand...

Thanks, I'll take that advice. I don't need to make more work for myself at this stage :)
 
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faztbullet said:
The hull could be MFG idea to add air into water steam tp loosen up hull or a molding/layup problem(my bet).....The carbs wont make any difference except a little mid-range grunt. Going to burn 7 gallon of fuel @WOT no matter if 1974 or 1994
Click to expand...

Thanks. I was concerned that the curve in the hull was damage that would need to be fixed.
 
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