1993 115? or 90......

[Mike Lammert]

Ok, I have a 1993 johnson 115 (j115tlats on the plate), that I have had about 5 years. Until recently I didn't question anything, as it ran pretty well, I just felt that it should push my boat a little better than it does. I recently noticed fuel leaking from the plastic carb bowls, and after research I found the correct new aluminum bowls, and the correct size orifaces in the correct new thread pitch, or so I thought. After having local shop do carb rebuild, it idles like a dream, however I don't think it feels quite right, as there is a midrange shudder and sloppy top end...I recently bought a omc manual for my motor, and when looking at the pictures my motor doesn't have the bubbleback exhaust cover....its flat like the 90...so that made me go look through the box, as I kept the old carb parts.....I now see the old bowls had 26c and 56c orifaces, consistant with a 90....i had 25c and 67c installed as this is what comes in a 115..so from what I can gather I now have a 90 powerhead on a 115 bottom with 115 orifices in a 90hp carb......what should I do now? I am thinking about researching the 26c and 56c in the new thread pitch to get it back to 90 hp specs as it ran better before.....do I make any sense? Any opinions?

 

[emdsapmgr]

Re: 1993 115? or 90......

The swapout of fuel bowls is normally a straightforward process, as you have assumed from the start. I would agree with your evaluation about your powerhead: Likely you have an engine with a replacement powerhead on a 115 midsection. The carbs you thought you were buying jets for are the wrong throat size. 115 carbs are probably 1 5/16" throat size and could flow more air to go along with the larger fuel flow from the 115 jets. A 90 carb has 1 3/16" throats and will flow less air, so needs the smaller jets to match the lower airflow. If you get the wrong jets in the wrong carb-it's a noticeable problem: The 115 jets you've installed now are probably overfueling-a problem which becomes more noticeable as the engine increases in rpm's. All is not lost. You should replace the 67C jets with the 56C jets, to put the new alum bowls back to the old 90 hp config. They are the same thread size. I'd also swap the mid jets back to the 26C also-if they fit. [Some of the direct replacement alum bowls (v6 models) use a different jet thread size for the mid jet, so your 90 mid jets may not fit.] Hopefully they will, but if not, you may not notice much difference if you leave the 25C jets in..You've done a good job of describing the jets by the "C" designation-the difference being the machined thread of the outside part of the jet. The only real difference between a 90 and 115 is the block porting, carb throat size and the bubble back exhaust.

 

[Mike Lammert]

Re: 1993 115? or 90......

The old plastic bowls had 14/20 thread pitch for both mid and high speed jets....the new aluminum bowls has an 8/32 thread for both....the ones with 8/32 have no A, B, C, D designations so I believe I am going to order #26 (0324652) and #56 (0333982) orifices from the research I can gather. I am thinking of attempting this myself as it seems straightforward...a couple of questions though. The carb kits were installed about a month ago, are the bowl gaskets reusable or should I get 2 more kits? Do the mid or high jets do anything at all during idle or no? This is just for my understanding, as they both take the same idle jets anyways.

 

[Mike Lammert]

Re: 1993 115? or 90......

Does anyone else have a 90 hp that had plastic bowls and converted? If so, do you remember the part numbers that you used? Or maybe there is this info somewhere among the vast amount of info here on iboats? I would just like to know I am ordering the correct stuff.

 

[emdsapmgr]

Re: 1993 115? or 90......

You should be able to re-use the rubber bowl gaskets. They are very durable and will seal well for years-as long as the mating surfaces are flat/parallel. I've replaced a set of V6 bowls on an 89 175 a number of years ago. Each hp and model year engine is designed for different jets, so there is no standard replacement scheme. The factory parts diagrams show the correct jets that are standard for a family of hp engines for each model year. Sounds like you are working from the factory exploded parts diagrams found on this website: epc.brp.com. The factory service manuals all for these model years usually show the master list of OMC jets that their engineers select from, broken down into these 4 thread size categories: 8-32, 1/4-20 D size, 1/4-20 C size, 5/16-24. There must be 150 various jet sizes listed in total. Again, my memory of the V6 alum bowls was that the mid jet changed to an 8/32, but the high speed jet was still a C size-meaning it can be reused as is.

 

[Mike Lammert]

Re: 1993 115? or 90......

Yes sir you are correct. I am using exploded diagram parts list to find orifice size, and the omc manual to find correct thread pitch/orifice part number. The only red flag to me is that 0333982 is called "orifice plug", all others, even the same orifice in the old (1/4-20) thread are just called "orifice". Maybe this is just terminology, but why differ? I think I am going to double check with brp tech service this afternoon.