'97 big 25 HP carb and intake

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nccatfisher

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Ok, it has been determined that my motor is actually a '97 model and it does have the small bore carb. I have been cruising eBay religiously and even going to the vendors "other" sales looking for a comparable big bore 25 carb or 30 carb. From any models that use a primer instead of have an actual choke. No luck. Do any of you guys have any ideas where I could look? I am happy with rebuilt, used, rebuildable. I still am not in a big enough hurry to shell out for new stuff but will prior to cool weather getting here and when I really want to be using it.
 
onthewater102 said:
Make? Model? Serial #?
Johnson, J25TELEUM, Ser# G0482792 You can see by the pic. that it has the small bore carb. Not the larger one like is on a 30HP


Large and small bore side by side for comparison. Mine is easily identified.
 
Last part that I could not find anywhere was found at a local boat shop that had been in buisness since the 60's. Call local. You may surprised because they don't advertise what's in their collection.
 
Stumpalump said:
Last part that I could not find anywhere was found at a local boat shop that had been in buisness since the 60's. Call local. You may surprised because they don't advertise what's in their collection.
I have tried that. Most of the time I get "we don't have anything that new here".
 
FYI you need more than a carb to do a 25-30 conversion on a johnson - the 25 and 30 hp have different intake manifolds (intake manifold assembly diagram) and different bypass covers (crankcase & piston assembly diagram) - I didn't see any other part differences in the diagrams on www.marineengine.com looking by your model # but I could have missed something.
 
onthewater102 said:
FYI you need more than a carb to do a 25-30 conversion on a johnson - the 25 and 30 hp have different intake manifolds (intake manifold assembly diagram) and different bypass covers (crankcase & piston assembly diagram) - I didn't see any other part differences in the diagrams on https://www.marineengine.com looking by your model # but I could have missed something.
Yeah I have been searching for the intake also and am aware that I have to advance the timing.

I am about to ditch the whole effort I believe though. I ran across a guy this weekend that has a '00 model 30 HP Johnson and he was kind enough to let me put it on there and see just how much difference it would be. It was a whopping 1.5-2 MPH top end and almost no appreciable difference as far as power and aceleration. His has a tiny tach on it and I know his is turning correctly.

I think I am just going to save my money and go with a 40 a little later on, I was going to convert mine to power trim, to I made all these mods I would be better off just selling mine and buying one with what I wanted on it.
 
I once read a detailed boat test by noted marine author Bob Stearns where he put a 75, 90 and then 115hp OB motor on the SAME boat and took the time to rig each at the BEST height & with correct prop.

The 115 was fastest, of course, but by 5mph. At cruise, the 90 was only 1-2 slower but had a batter fuel economy. Hull design is typicslly the limiting factor in 'how well' given horspepower will push something ...
 
Out of curiosity, do you recall if those three motors were all from the same series class so there wouldn't be much difference in the weight of the motor for the 75 vs the 115? I know my 60hp late 80's merc weighs the same as the 50hp of the same line, but 75-115hp seems a much larger jump & it might have added a lot of weight in the process to only have achieved 5 mph difference.
 

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