88 Evinrude 48 SPL - correct orifice sizes?

[Darren418]

I am rebuilding the carbs this winter to give me something to do. The motor runs great but has always seemed a little too rough at idle. Misses, coughs, etc., but smoths right out as soon as you give it throttle. Hopefully the rebuild will solve that problem especially since I troll a lot. I've had the motor a year and I don't think the carbs have been rebuilt for awhile, certainly not since I've owned the motor.

I took the air silencer off an noticed the low speed orifice on the top carb was marked 29. Isn't this a little too small for this carb? Perhaps someone switched them out as an easy fix to a lean running condition? When I rebuild the carbs, I plan to replace the orifices with the correct size as I assume whatever the problem was that caused the lean running condition will be solved by the rebuild (partially clogged idle fuel passageways, my guess) and i should be able to go back to the stock orifice size (right?).

Question is, what i s the correct low speed orifice and high speed jet size? I'm guessing the low speed is supposed to be 36. Also, do the top and bottom carbs use the same size orifices? I would think so but want to make sure.

Also, when doing the rebuild, should I bother removing the metal disc with a punch as per the OMC manual and replacing it with a larger flat punch after cleaning and sealing with Gasoila? Yes, that's what the manual says, but do I really need to bother?

By the way, engine model is VE48ESLCCC and both carbs are stamped N431995 and are the style that have fixed low and high speed orifices.

Thanks for any help. This forum has already been a great help to me by just reading all the informative posts.

 

[OBJ]

Re: 88 Evinrude 48 SPL - correct orifice sizes?

The parts breakdown says the idle air jet should be a #36 (PN 323703) 'bout $6.70 at a J/Rude dealership.

It's possible the previous owner or possibly mechanic replaced the jet to cure an idle problem and just made it to small.

Do make sure the link and sync is correct. One throttle plate open a tad could cause the problem also. Also make sure the fuel system is in good order, hoses are still good and there are no leaks. Check the ignition system also for good spark. May not even be a bad idea to get a compression reading on the holes.

On very few occasions, I have replaced idle air jets to correct idle problems but ONLY after exhausting all other efforts to correct the idle problem.

 

[Darren418]

Re: 88 Evinrude 48 SPL - correct orifice sizes?

Thanks, OBJ. I already did a good link and synch. Took the time and got that pretty much perfect. Adjusted WOT timing and pickup timing and both are spot on. Checked fuel system for leaks or obstructions and found none. I did not thoroughly check the fuel pump yet, other than check that it has no obvious leaks. I didn't bother more with the fuel pump figuring since midrange to full throttle is butter smooth, the fuel pump must be ok (could pump problems show up first at idle??). I checked spark by pulling each plug wire at idle. Engine sputters and runs like crap when either of the two wires is pulled, indicating both cylinders are firing. Compression test done in May and showed 160 on both sides. Sorry I didn't give all that background in my first post. I'm pretty sure the carbs just need a good rebuild, but following your advice, I'll take a closer look at the rest of the fuel system and change the plugs for good measure. Ignition problems are relatively rare and not likely to cause rough idle, though, right? Could a weak coil only make itself itself known at idle? Honestly, I didn't even think of ignition, assuming carbs the whole time! :$ I run a farm and do all of the work on a variety of small engines, including chain saws, pressure washers, etc., but I am relatively inexperienced with outboards. Seems pretty straightforward though especially with the OMC manual which is very good. Thanks for the help.

 

[OBJ]

Re: 88 Evinrude 48 SPL - correct orifice sizes?

The 48SPL's are a pretty straight forward engine. Sounds like you covered bases pretty good. I think I would spring for the correct larger orifice and see what the engine does. The carb rebuild is a very good idea.

 

[Darren418]

Re: 88 Evinrude 48 SPL - correct orifice sizes?

The correct size orifices, #36, should be arriving in a few days then I'll dive in and rebuild those carbs. I also got a pair of 32's for experimenting with a slightly richer mixture in case it likes it better. It'd be nice if the idle mixture was adjustable on these carbs, but I suppose it's simpler and more "proper" to get the carbs running like they should using the stock orifices. If the carbs (& gaskets) don't leak and are clean, the engineers knew what size orifices it would need.

Yes, the 48 spl is silly-simple good old-fashioned American engineering. No computers or electronics, no power tilt and trim. I don't know why anybody would want power T&T on a motor this size...it's quite easy to do manually. A couple of simple single barrel carbs on two cylinders, mechanical linkages, no worries about emissions back in the late 80's, so no complex emissions controls or other extra garbage...I love it!

Thanks again OBJ.