Proper carb jet size 94 88spl

boredindaboro

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Hello,

With the help of many folk on here I finally have my 88 SPL back up and running. It runs very well after I swapped out the carbs for older 115 carbs due to ethanol eating the plastic bowls on the old carbs. The problem is it now runs rich. I need to know what sizes the original jets were so I can order the equivalents when I rebuild these. I don't need a part number just the sizing as I imagine the older carbs will have a different part number for the jets. I have reproped and made no rpm difference. Thanks for everyone's help in advance
 

boredindaboro

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Thank you so much. I will post a model number of the old carbs on Wednesday. I assumed the mains were different. This way I can order the proper rebuild kit and jets.
 

emdsapmgr

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You need to be careful when rejetting. If the older 115 carbs have a larger throat (venturi) than the 88 carbs, you'll be leaning the carbs out by putting 88 jets back into a 115 carb body. Check the face plate of the carbs. The venturi size is cast into that front flange. The carb size may vary between 1 1/4" up to 1 3/16" or even 1 5/16".
 

boredindaboro

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So is there an equation that will determine the proper carb jet size if the venturi is different? I know it's been a long while since I've been on here but life got in the way. I'm sure it's running rich just not sure how much smaller a main I need to install. I'm down about 1200 rpm at wot. It also has a hard time restarting if I throttle down quickly and shut the engine off. (like when my local wildlife officer pays me a visit) it restarts but acts like it's flooded
 
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jimmbo

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The 88 uses a 1 3/16" carb, but so does an early 115(1969 - 1970). From 1973 onward the 115 uses a 1 5/16" carb. Unless the 88 block is ported to match a 115/140 block the bigger carbs are actually a performance reducer. The engine can't inhale or exhale well enough to utilize the bigger carb.
 

boredindaboro

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So would a slightly smaller jet help or would a reducer of some sort on the opening of the carbs help. Best I can get is about 4500 to 4600 rpm then it loads up and coughs. Going back to the original carbs is not an option as the shop who changed them probably doesn't have them and they needed a complete retro fit due to the plastic bowls splitting due to age and ethanol. If I could get another 500 to 600 rpm and better hot starting I would be happy. Great old motor resurrected from the grave otherwise
 

Faztbullet

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Need to know part number or replacement carb and venture size stamped on front of carbs...
 

jimmbo

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Just curious. What WOT RPM were you getting with the original carbs?
 

boredindaboro

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Not sure what WOT I was getting with the original carbs. Boat never ran right and the one time it ran ok the tach was dead. I have family who will not go out on the boat as it left them stranded too many times. Lol. All the tech specs I have looked up say it should do about 5800 rpm at WOT. So I figure I'm down 1200 to 1400 rpm. If I could get half of that back I would be happy. I've been told that any lower rpm at WOT could damage the engine.
 

jimmbo

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The WOT range for that engine is 4500 - 5500. That engine actually makes its best power around 4800 rpm. If you prop it to run higher, it will actually be making less HP as its porting and port timing are too restrictive. Since you say the engine has never run right, your issues might not be the carbs. Was the entire fuel system checked over? What are you basing the 'rich' condition on? How do the spark plug look? Are the floats set properly? Is the spark advancing correctly, as in sync with the carb opening and its full advance setting?
 

ondarvr

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I think I have a set of carbs of a 94', I'll check them tomorrow and see what jets are in them.
 

boredindaboro

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The entire engine has been gone over. Started with compression check, then resurfaced heads, New head gaskets, flushed tanks, New lines, New water fuel separator, New fuel pump, New cdi, New coils New plugs, New water pump, wear plate, carbs, had cabling reset and synced, New prop (went to a different pitch to increase rpms. Did not change the rpms) currently hard to restart hot acts flooded, plugs are almost black but not wet, and stumbles if I push the throttle to WOT. I can slowly push throttle to max rpm which is about 4500 rpm. Also if I pull a tube behind it acts like it's loading up. Will clear out on its own after a run without the tube.
 

jimmbo

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Do those carbs use an enrichment system instead of a choke? If so, is it functioning correctly? A a high float level, or heavy floats, wrong gaskets used or missing gaskets in a rebuild can cause a rich mixture
You said you changed props but no rpm difference? What was the old prop and what was the new one? Makes, AL or SS, model, pitches?

What were your compression numbers?
 
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ondarvr

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Looked at the 94' carbs I have, 1 3/16" and 58C main jet. Didn't have time to dig deeper.
 

boredindaboro

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Compression is approx 120 across all cylinders (analog gauge all nearly identical) it could be a timing issue but only at wot would be a weird issue and other than the mentioned issue it runs well. As far as the carb gaskets, I was told the carbs were just done, but I plan on ordering a rebuild kit and rejetting at the same time but the jets seem to become a complicated issue. The props are aluminum as I run in shallow water fishing, but I'm sick right now and will not be able to get the pitch numbers tomorrow
 
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