69 Merc 500 saga cont'd - NE1 near Baltimore?

[tredragon]

So here's the short version of my story:

First boat. Just got it a few weeks ago. 68 Larson All American (Lapline hull). Great potential but since I don't have a lot of time or money, I'm just trying to enjoy it as much as I can for now.

First it wouldn't pee... pulled LU and everything was fine. Cleared tell-tale and she started peeing. Unfortunately I had the shift shaft stuck in forward gear, hard to start (cause it was always in gear)... ran battery down, stuck in middle of lake... dropped LU, fixed that. Took her out yesterday, happy to have a properly working engine.

Now to the current problem... She starts, might take me 2-3 times and I have to choke if she hasn't been running for 10 minutes or more... but that's no big deal... now, when she's started, I can throttle up in Neutral and she's fine... I can put her into gear, just first click into either gear... still runs. When I throttle up the controls in gear though... she sputters and stalls. I was able to get her moving a few times with a combination of throttling up in Neutral and letting her "warm up".... then putting her in gear (after throttling back down of course)... and the other few times I had to basically throw the controls way fast and hard deep into throttle and she'd go.

I'm a beginner at this... but since it throttles up fine in N but not in either gear... I'm wondering if the linkage somehow isn't giving her enough juice in that first band of gear... Or is it maybe the idle is set too low? Running rich?

If anyone is near baltimore... I'm looking for help not only with the troubleshooting of this boat which we all know there will always be something... but also someone who's boated a day or two and would like to actually go out on the boat with me!! My wife and youngest son, 2, don't always want to go... leaving either just myself, or my 6 year old and I to put in, take out, and fish, putt around alone.

Thanks in advance!

 

[emckelvy]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

So you're saying that you actually got past the "idle bog" a few times and then it ran OK? If so, sounds like you may have a combination of too-slow idle speed and too-lean idle mixture.

The fact that you have trouble restarting after sitting only 10 minutes leads me to believe it's lean.

Adjust each idle mixture screw 1/2 turn CCW (rich) and see what that does. It should be easier to start, restart better, and take off better. You may also have to adjust the Idle Stop to get a stable idling speed.

BTW if you put the control box in Fwd with the engine stopped, you can advance the throttle all the way and watch the action of the distributor and carbs, to see if they're moving as they're supposed to. Look down the carb throats and you'll be able to see the butterfly valve opening.

G'luck.......ed

 

[dlplost]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

Yup, sounds like your idle mix is too lean. Seems lots of people like to play with that trying to stop it from smoking at idle. It works best if it is a little on the too rich side rather than on the too lean side.

 

[tredragon]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

yeah, it starts (kinda hard though) and will throttle without missing a beat in neutral. I can kick it just into either gear and she'll stay running... however any bump up in throttle once in gear makes her bog and choke and puke. I've been able to (on rare occaisions) cram it to near WOT in forward and have her take off... once in gear though, it's the lower RPM's (but beyond idle) that stall her out.

I'm going to take your advice and first look at how the dist. and carbs act when throttling up in gear (engine off). It was like the throttle didn't start going up soon enough as the control advanced. Maybe there's a gap in there... I'll also throw the muffs on and check the idle mix screws. I think I can figure those out since they all seem to be labeled.

So... anyone near Baltimore that finds themselves on a boat alone alot? I could sure use a first mate. And the Doctors say I'm past that whole psychopath thing too... ;-)

 

[tredragon]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

ok, so I have 3 labeled screws. Throttle stop, Idle stop and spark advance. I'm guessing retarding the spark advance makes her run more rich?

 

[Yepblaze]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

No.

but opening up the idle mixture screws might help a little.

 

[tredragon]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

okay, so i noticed a couple of things...

first, (this probably doesn't matter) the electric choke solenoid seems to move an arm that closes the top carb. This arm is supposed to be connected to another shaft/arm that runs down to the bottom carb. This second shaft/arm is also what goes up to what I'm assuming is the manual choke button on top of the powerhead... and I say that because it does the same thing the solenoid would but if you didn't have power to the solenoid...

Secondly, I see set screws on top of each carb, kinda right above where the butterfly is, and they run perpendicular to the ground (up and down). I also see, when looking from the transom through some small holes, back to the carbs, a set screw on each carb that goes horizontal to the ground. This second one is recessed quite a bit while the top ones portrude 1/8" or so.

Are either of these the mixture screws?

 

[emckelvy]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

Take a close look at this parts diagram of a typical 50 HP carb. Piece # 26 is the idle mixture needle and if you follow the line from the needle you'll see where it goes.

http://www.mercruiserparts.com/Show...ng&inbr=437&bnbr=11&bdesc=CARBURETOR+ASSEMBLY

Screw each needle "in" (clockwise - lean) until it seats lightly. Then back out 2-1/2 turns. This will probably be a bit rich in the water but she'll run and take throttle with those settings.

Now, one important thing, when you're running on the muffs you have no backpressure or load on the engine. So any idle mixture adjustments you make in this condition are gonna be too lean to run the motor smoothly in gear in the water.

When I'm adjusting mixture and can't put the motor in a test barrel, I'll set the screws for best idle then go rich 1/2 turn. At least then it's gonna be close in the water.

At any rate, no matter what kind of adjustment you make on the flusher, you'll need to 'tweak' in the idle speed and mixture with the motor warmed up, in gear, in the water.

One caution, DON'T mess with the 'spark advance' screw unless you're setting up max timing. This does not affect idle functions.

Don't mess with the 'throttle stop' screw unless you're setting that up.

'Idle stop' is the correct screw for adjusting idle speed.

As far as choke setup, when you're at the above link looking at the carb diagram, look in the left-hand column and you'll see various other selections including "carburetor linkage and choke solenoid". This diagram shows all that stuff and how it relates.

And if you go here http://www.mercruiserparts.com/selectSerailRange.asp?doc_nbr=500 and click on the serial # range that corresponds to your motor's serial #, you have the exact parts diagrams for your motor.

Give that a shot and see what happens...........ed

 

[tredragon]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

oh, and I forgot to mention when I was talking about the choke... the choke linkage that connects both carb's choke valve... the pin that holds it into the top carb's choke valve is broke. So, either manual or electric choke, the bottom carb is the only one getting choked. when I get the mixture good... is this worth addressing or only if she doesn't start well cold?

Once again Ed... you're the bomb.

 

[emckelvy]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

Well, it's gonna start a lot better with both carbs being choked, aint it???

If I recall that's a little stainless pin, don't know if you can find a suitable replacement elsewhere but you know what, seen plenty of 'em come in with a small nail or brad taking the place of that pin. It'd do in a pinch!!!

 

[tredragon]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

I think I'll do that. I'll just keep some small brad nails and maybe a few paperclips around. Never had a chance to adjust the idle mix cause the darn rain never stopped last night.

 

[tredragon]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

okay so i just screwed them in until they lightly seated and it was only about 1 1/2 turns. if it ran, albeit a little lean, at those settings... should I try 2 turns? I'm going to get my trusty trash can and see how she runs... but there isn't much circulation in there so it still won't be very indicative.

oh, and a "picture hanging nail" that come with those little G shaped brackets for hanging light pictures in drywall... that fit in the choke linkage and I bent it 90 degrees to keep it in. it doesn't rub on anything either so I'll try that and see how long it lasts.

 

[tredragon]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

I went in until they seated, it was slightly more than one turn. I backed them out each to 1 1/2 turn, then started. Idle was slightly rough so I adjusted idle stop. All of this was, mind you, in a trashcan full of water. She shifted into gear and through the powerband just fine in either gear. Also, fixing the upper carb choke linkage and the new mix settings made her fire right up (choke for 3 seconds first start... then fired up within a second each subsequent start).

I'm faunching at the bit to take her out on the water (equipped with my long flat screwdriver of course) and test out the mix settings.

I set both carbs to the same mix setting, as far as number of turns rich from full lean... my question would be... how would I know if one needed adjustment over the other... a different adjustment?

 

[emckelvy]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

What you just did is only an initial adjustment and I'm thinking 1-1/2 turns is probably still too lean but see what happens.

Once you're in the water, you'll still need to warm the motor up, get it to some kind of idle speed where you can adjust the carbs, stick 'er in gear and start tweakin'!

Adjust one carb at a time. Adjust mixture for fastest idle. Once you've got that carb idling as fast as possible, turn the idle screw in the "rich" direction, maybe 3/8 turn to 1/2 turn. This must be done in order to make it rich enough for the motor to be able to start well cold, and also accelerate ("hole shot").

Once you've adjusted both carbs this way, attempt to accelerate and see what she does. If it still bogs, adjust each needle CCW another 1/8 turn and see what happens.

If you need to, repeat a couple more times but by then it'll probably be plenty rich. Of course, if you keep adjusting the carbs rich and it doesn't help, that's not working for you either!

But I bet once you get the carbs dialed in, it'll run real nice for ya.

G'luck.........ed

 

[tredragon]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

Sorry for the hiatus to the thread. I spent all day yesterday doing fiberglass keel touchup and building a custom back seat (bench) that folds up to gain access to the stern/transom.

So where I put in I have to idle (no wake) for a good 10 minutes before I can get out to the lake from the creek. That should be plenty of time to warm up. As I near the lake, I'll start fiddling with the carbs.

I guess I still don't understand how to tune each carb... I mean, how to know how each carb is individually running to make adjustments to them separately. My initial plan was to just get done idling through the creek, then gradually increase throttle in gear as I normally would when exiting the no-wake zone, and see if she bogs. If not... I'll go back to idle and then try a good hole-shot and see what happens. In either case... if she bogs, I'll adjust but again... how to know which carb needs what?

 

[emckelvy]

Re: 69 Merc 500 saga cont'd - NE1 near Baltimore?

As you start with one carb, and turn its idle mixture needle in and out, the engine should respond accordingly and speed up/slow down as you're going lean and rich. The "happy spot" where the motor really likes what you're doing, is when it's running the fastest as you're making this adjustment.

So, you've just 'tweaked' one carb needle to achieve the best rpm that you can. What next? Well, this "ideal" adjustment, while it makes the motor idle nice and "crisp", is too lean to allow good acceleration. Your outboard's carbs don't have an accelerator pump, as do automotive carbs.

So, you've got to make things 'less than ideal' by richening up the idle mixture on the carb you've just set up to be ideal ! But that's just the way it is with these. If they're too lean they'll bog. If they're too rich they won't idle very well at all but at least they'll cold-start real good!

So there you are, you've got one carb all nice and adjusted to the "slightly rich" setting that'll allow a bog-less takeoff.

What to do next? Well, go to the next carb and repeat the same thing you just did with the first!

And after you do that, the motor's probably going to be idling a lot different than it did before you started. You may need to adjust idle speed. Typically when you get the carbs 'tweaked in' it'll idle faster. But you might need to bump up the idle speed. Whatever the motor wants at this point to idle well enough in gear that it doesn't stall.

At this point you're done. If you had an Inline Six, you'd still have one more carb to adjust. Fun, eh!

So, now we think we've got a decent carb setting; see what happens when you accelerate. If it takes off like a banshee you're good. If you still have a hesitation, you might still be a bit rich.

So, what now? Well, now you're into the Fine-Tuning part of this thing.

Remember when we first adjusted the carbs? Well, now they're both set pretty much the same, "slightly rich".

Now we're gonna make them even more "slightly rich". Do this by turning each carb's idle mixture screw the SAME amount, say 1/8 of a turn CCW (rich).

Why turn both screws the same? Because we just went thru all the trouble of getting both carbs tuned "about" the same, if we started making different turns on each one they'd be Out of Whack, wouldn't they?

Time to check acceleration again, if you're Bog-Free you're done.

If not, try another 1/8 turn Rich on each mixture screw and repeat acceleration test.

Obviously if you do this 8 times you're going to have turned each idle screw out another turn and that's usually too much. And it'll probably be so rich it won't idle anyway.

At that point you've got to say that there's something else wrong and start looking at other things.

But you have to go thru this tuning process whether you're troubleshooting or just setting a motor up to run well.

Once you're done you're gonna have a lot more info than when you started and that'll help with the diagnosis if there's still a problem.

Anyway, that's enough words for one post I expect, hopefully that explains things a bit better for ya..............ed