200 2.4 carb question

[123trentm]

Hi all. I have a 1988 200 2.4 mercury. Compression is 140-145 on all cylinders. I bought this powerhead used, so I dont know exacly what work has been done to it. I know the heads have been off due the studs and it has carbon fiber reeds. now my question. Currently the jets on the carbs are as follows; #1=82 #2=80 #3=80 #4=80 #5=80 #6=74. Does this seem right? I thought #1 and #5 were supposed to be rich. Any advice would be greatly appreciated. Thanks

 

[j_martin]

Re: 200 2.4 carb question

The base jetting depends on the carbs. Different carb numbers in the same application could have vastly different jets. That wide a range in jetting on a single engine does not seem right.

On some engines, 2 and 5 are jetted slightly richer. Which carb bore is different depends on if it's a vert reed or horizontal reed engine.

At that compression, your minimum octane would be about 92. Anything less will hurt the motor.

Obviously someone has been modifying that engine. You need to identify
1. The actual carb model on the engine, and that all 3 are the same.

2. Timing settings, Idle, throttle pickup, and WOT, and what advance modules if any are on it.


Set up right, you got a real hummer of an engine. 1 lean cylinder, or timing off and you've got a grenade.

hope it helps
John

 

[123trentm]

Re: 200 2.4 carb question

Timing is good. module removed. carbs all the same. Are you sure that 2 and 5 run rich? I was told that 1 and 5 run rich. I was thinking about getting another 82 jet and replacing the 74 with it, but I want to make sure which ones to run rich/lean. thanks

 

[j_martin]

Re: 200 2.4 carb question

Timing is good. module removed. carbs all the same. Are you sure that 2 and 5 run rich? I was told that 1 and 5 run rich. I was thinking about getting another 82 jet and replacing the 74 with it, but I want to make sure which ones to run rich/lean. thanks

On a horizontal reed engine, the upper left carb, looking at the front, is #2. On a vertical reed engine, the upper right carb would be #2.

On the charts I have, if anything is richer it's #2, then #2 and #5, usually both main jets and vent jets. (Vent is usually omited completely for the rich cylinders.)

Brace yourself, somebody with a dremmel tool and drills may have totally hosed that carb. Also it could be a 74 jet drilled out to 82.

If you can tell me the WH number for your carbs, (or all the numbers on any one carb, it's imbedded there somewhere) I could tell you what it came off from, and it's natural jetting. If you're going up in HP, you'd probably want to start out a little fatter than normal.

Then put new plugs in, run the engine a short time WOT, and kill it at WOT with the switch, (or kill lanyard) if possible, or shut it down as quickly as possible. Get to shallow water or a dock so you can pull your plugs and read them. If possible, also look in the cylinders and look at the pistons.

Good running would make the plugs a grocery bag brown, and the piston would be wet for about the size if a quarter near the intake port. A little wetter is OK, dryer will burn a piston. There's a fine line between peak performance and grenading the powerhead. Unless you're racing, run it a little fat. Keep in mind that if you tune for peak in warm water, you're likely to be too lean if the lake is cold.

Normally, if you peak tune an engine, it will wind up a little leaner than factory, and vary 0 to .004 between cylinders. It depends on a ton of factors, including port placing, liner rotation, compression between cylinders, and cooling efficiency cylinder to cylinder. The pro's say, "Read the plugs and pistons and give it what it wants."

hope it helps
John

 

[123trentm]

Re: 200 2.4 carb question

Where the carbs bolt to the intake every carb reads 13745427 WH. On the outside above the butterflies top carb reads 46 10899, middle carb reads 46 20969, and bottom reads 46 31049. I took the jets out and the 074 looks as big if not bigger than the 082. It is a horizontal 7 reed cage. When facing the carbs top left hand corner is 082 and lower right hand corner is the supposed 074. I am not after a race motor, I want a good, reliable, strong motor. I am hanging it on a 1976 18' 6" ranger. I appreciate all your help J.Martin.

 

[j_martin]

Re: 200 2.4 carb question

Those are WH 46 carbs, and are for your engine.

Stock Jetting is
Mains .080, except 2 and 5 are .082
Idle .056
Vent .096, except 2 and 5 are none

I'd guess your heads have been shaved a bit. I would run .082's in the mains, and check the plugs after a WOT run in cold water, and increase any that seem a little lean to .084's. If .they all seem rich and you want a bit more, go down carefully in size.

The .072 has been drilled. Replace it with a new .082

I would run 92 octane or better gas in it, preferably without alcohol.

Prop it for about 6,000 rpm

Should go like a bat out of hell.

hope it helps
John

 

[123trentm]

Re: 200 2.4 carb question

Where would I purchase new jets? By the way, are you the same j.martin off scream and fly? thanks again j

 

[j_martin]

Re: 200 2.4 carb question

Where would I purchase new jets? By the way, are you the same j.martin off scream and fly? thanks again j

Yep, same old geezer.

Buy from Mercury. Only reference I have is an image imbeded in a doc file. It's 23 kb so it won't upload. Got it from BigHammer, and the page is down.

.080 is 1395-6201
.082 is 1399-3518
.084 is 1399-3517

They're about 3 bucks each.

hope it helps

 

[j_martin]

Re: 200 2.4 carb question

Try this: System won't let me upload a decent quality .doc file with the info, but I can degrade it into a fat jpg file and it goes.

sheesh

 

[123trentm]

Re: 200 2.4 carb question

Thanks for all your help J