carb adjustment for altitude?

[iaonbb]

Hey all, here’s my dilemma…I have the 310 carb engine. 10 hours thus far. Followed the break-in schedule religiously. Here are the symptoms I’m experiencing:

1. Won’t idle at start-up. Must run in neutral at 1k rpm’s for a couple minutes before I can do anything.
2. Acts like it wants to die when shifted into gear and/or trying to idle out of the no-wake zone
3. Runs very inconsistent overall, e.g., rough, surges, grinding noise? etc..
4. Idles perfectly after running 3-4k rpm’s for a few minutes and then returning it to idle, e.g, stopping to pick up a rider, etc… then, starts acting like it wants to die again after another few minutes.

History: It’s an ’04 that I just bought new. Guessing it had gas sitting in it for extended periods of time. I’ve ran 2 tanks of premium through it, the second with a bottle of dri-heet to try and absorb any moisture in the tank/fuel that might be causing any issues. No change whatsoever. Going to run a 3rd tank through tomorrow with a can of seafoam to see if that helps. At this point, I’m thinking it may need some minor carb adjustments. I’ve spoken with my dealer who said it sounds like it might be running rich, which makes sense at this altitude. I’m scheduled to have it in the shop at the end of the month for the 20 hr service and winterization. I planned on having him adjust the carbs then, including drilling out the caps to access the bleed screws if necessary. Sounds like carsondoc’s post from ’03 best matches my situation.

“YellowMoomba,
I was having all kinds of engine problems at slow speeds and idle until I adjusted mine. Now you can barely tell the difference between this boat and an EFI engine. Runs great. I live at 4700 feet and often operate the boat at 6200 feet."

However, I was hoping I might be able to make a few adjustments to the idle, air/fuel ratio, etc. myself first, without resorting to drilling. We’re heading out tomorrow for the first day of riding after the break-in and I would like to try and tweak it a little while we’re out. I know very little about engines but I’m sure I could turn a few screws here and there. Anyone care to help out a newbie with some “carb 101” advice. Step-by-step inst’s would be most appreciated! Need to know by tomorrow a.m. if possible…many thanks in advance!!!
MDB

[carsondoc]

Hi ia. It does sound like you are having the same problems I encountered. The first thing I did was have my dealer try to fix it in the shop. He increased the idle speed a little and advanced the timing a little. Unfortunately, these changes made only little difference. The problem with just increasing the idle to fix this is that you will start putting more stress on the transmission when going from idle to "in-gear". That's why it's not recommended to increase your idle rpm above 1100 (actually, it shifts smoother when your idle is about 6-700 rpm and is probably better on your tranny).

With that said, you can try to increase your idle rpm a little (you said you were already idling at 1000 rpm?). The screw is on the port side of your carb. You can figure out which one it is by taking the air filter off your carb and looking at your accelerator linkage on that part of your carb. With your boat off (in the garage maybe) just look at your carb while someone accelerates/decelerates a couple times. It should be fairly obvious--it's a big screw that stops the accelerator mechanism on the carb. Then, when you are in the water idling, take off the air filter and turn the screw a little while you watch your tachometer. Obviously, be very careful around the front of your engine where the parts are moving.

I would not increase it above 1100 idle rpms. When you shift into gear you will drop a couple hundred rpms. If this does not fix it, adjust the idle air-bleed screws and get your idle back down to 700 or so.

Good luck and I'm sure with some tweeking you can get your boat running great.

[iaonbb]

Thanks buddy...never guessed you'd still be on, lol! I should be more clear...I normally idle around 700'ish or so I think. Right after startup, I run it in neutral (using the tranny disengare at the bottom of the throttle) at 1k until it will idle decent.

So, my only two options are either the idle speed or drilling out the caps to get to the bleed screws? I was hoping there was some sort of air/fuel mixure screw or something that I could adjust as well (or is that what the bleed screws are)? I know I can't adjust the timing, right?. Many thanks for the quick reply!
MDB

[rbc_racing]

I had the exact same problem on my 04 that I bought this year. It just needed a slight adjustment of the idle mixture screws under the caps. There was another thread about this posted not to long ago where the indmar rep said it was ok to adjust them as long as you don't live in cali. I started out by screwing them in all the way and backing them out 1 and 1/2 turns, then fine tuning the adjustment on the lake after that. It runs great now, It acts just like and EFI engine now.

[carsondoc]

Ia, the air/fuel mixture screws are the idle air bleed screws--same difference. It's actually a very simple process. It's just a matter of popping the brass caps off so you can get at them. Everyone on this board talks about drilling them out but I have to admit that I was skiing with my dealer when we did mine and all we had was a rock and a screwdriver! What ever gets 'em out! As RBC can attest, it makes a world of difference. You'll be a happy camper.

Go ahead and try the idle adjustment first but if that doesn't cut it, just fix the idle air-bleed adjustment and you should be good to go.

[YellowMoomba0]

You and I are at much different altitudes. Me about 360. The idle screw did nothing more than raise the rpm and make the tranny plates slam into gear. As well, idle speed was too fast. I kept this setting all of 10 minutes. I know of no other way than to adjust the bleed screws. Then again, Im not sure how the altitude difference will affect you. All you can do is try it with the idle screw first. If I had to guess now, then Id say you will have to adjust the bleed screws to get happy about the performance. I would be interested to learn though if the idle screw adjustment alone would fix your problem.

[iaonbb]

Ok, so I printed the older post on how-to remove the brass caps...I'm out in my garage as I type, cover and filter off, trying to figure out exactly which caps we're talking about. I see two diferent sets of brass screws on the top of the carb (small and smaller), and four larger brass "leather tack" looking ones on the side. None of them look right?Where the heck are these things? Afraid to start drilling unless I'm 101% sure. Sorry guys, but engines are not my forte'

[YellowMoomba0]

Whats your email address, I will send pictures of the Carb

[iaonbb]

Found 'em! Wil report back later on how it worked out..thanks

[iaonbb]

Well, I'd have to say it was a success...Most noticeable diference was in the idle smoothness and puttering out of the marina. Also starts much better after being turned off for 5-10 minutes, e.g., switching riders, drifting, having a beer, etc. I did not touch the idle speed as it was around 8k and I though that was plenty high. Still needs a little tweaking though I think. I turned the bleed screws about a 1/2 turn out (counterclockwise) from their original position and noticed it smoothed out almost immediately. Didn't have to use the tranny disengage and pump the throttle and get it to re-start once!

So....here's my next question...what is actually happeing when I back the screws out (counterclockwise)or turn them tighter (clockwise)? Does one direction equal more fuel and less O2 and vice versa? I'd assume that backing them out (counterclockwise) increases the O2 and decreases the fuel? Does one screw control the air and one the fuel, or do they both do the same thing? Figure I could probably have her dialed-in by the end of day tomorrow if I knew exactly what was happening when I turn the screws one way or the other...any techies out there know?

In summary...this board rocks!!! Solved most of my probs and saved me the $95/hr labor!! woohoo...now what else can I buy for the boat with my savings :p
MDB

thanks guys!

[carsondoc]

Ia, That's great to hear. Make's boating much more enjoyable. Both screws do the exact same thing. I can't tell you if counterclockwise=more or less rich idle mix however. I'm sure a techie on the board can probably help.

[iaonbb]

Anyone? Bueller? Would be nice to add it to this thread for the record....Put another 3 hours on today with a little more tweaking...bottom line: ANYONE with the carb motor absolutely, positively has to do this "mod" if you wanna call it that. I can't friggin' believe the diference. So smooth, doesn't die, started right up this morning, starts every time after sitting for 10 min....unbelieveable!!! I can't even believe something so simple can have such a big impact. I'll have it in end of the month and all I have to pay for is the 20 hours service and winterization now...easily saved me a couple hundred bucks and a month of frustration. If anyone has been thinking about it but is on the fence, just do it!

[Wolf-]

Originally posted by iaonbb


Anyone? Bueller? Would be nice to add it to this thread for the record....Put another 3 hours on today with a little more tweaking...bottom line: ANYONE with the carb motor absolutely, positively has to do this "mod" if you wanna call it that. I can't friggin' believe the diference. So smooth, doesn't die, started right up this morning, starts every time after sitting for 10 min....unbelieveable!!! I can't even believe something so simple can have such a big impact. I'll have it in end of the month and all I have to pay for is the 20 hours service and winterization now...easily saved me a couple hundred bucks and a month of frustration. If anyone has been thinking about it but is on the fence, just do it!

It's on my list. Problem is, have a youth outing next weekend, and if I muck something up, I'll have 40 unhappy teenagers on my back. Although, I do have this Sat and Mon to "tweak it" if I wanted to.

Some one toss me some pics before I pull the air cleaner off and take a screwdriver and rock to it...
Er, I meant Craftsman tools, honest, I did...

[iaonbb]

Wolf~ There's no possible way to muck this one up...the little brass leather tack looking caps just smaller than a dime about 1/2 way on the carb and on towards the bow of the boat cannot be missed. They're identical on both sides of the carb. Just drill sloooooowly until you just pop through and then use the needle nosed pliers to pull out the caps. All I did was turn them about a 1/2 turn to the left (counterclockwise) from their original position while idling in the water. You could hear the improvement immediately. Took maybe 10 minutes and all of that was the drilling. Go for it man...you won't regret it or muck anyting up

[Wolf-]

Originally posted by iaonbb


Wolf~ There's no possible way to muck this one up...the little brass leather tack looking caps just smaller than a dime about 1/2 way on the carb and on towards the bow of the boat cannot be missed. They're identical on both sides of the carb. Just drill sloooooowly until you just pop through and then use the needle nosed pliers to pull out the caps. All I did was turn them about a 1/2 turn to the left (counterclockwise) from their original position while idling in the water. You could hear the improvement immediately. Took maybe 10 minutes and all of that was the drilling. Go for it man...you won't regret it or muck anyting up

1. Wife is out picking up pizza...
2. Wouldn't she be surprised to return and find the boat I just washed and covered, uncovered with engine cover up.
3. Better yet, the sound of electric tools...

You have convinced me. Will drill it out tomorrow morning and adjust this weekend.

[iaonbb]

LOL! I did mine early in the a.m. while the Wife and kids were upstairs sleeping so she wouldn't freak out when she saw me drilling holes in my new engine...haha...Seriously, so darn easy it stupid. Just get the caps off in the garage and do the tweaking once wamed up and on the water. I'm still amazed at the diference. Lemme know how it works for you? Where are you located? Altitude an issue for you too?

[Wolf-]

Originally posted by Ed G

why doesn't anyone post any photos of the location of these caps?

If they have, can someone please direct me to them.



Because you asked nicely.
Well, let me get you one thats zoomed in.
I was lucky, my caps were already off.
http://www.feather.us/wp-content/uploads/2006/09/WindowsLiveWriter/MoombaAdjustingtheBleedScrews_A3E8/IMG_7893%5B2%5D.jpg

[Wolf-]

Originally posted by Ed G


thanks!

Where are the brass caps in relation to the throttle linkage?

I think we need to document this procedure with as many pictures as possible.

Now that my boat is out of warranty, I'm getting interested in trying this.

I read where Brian Raymond recomended turning the screws all the way in, then backing them out 2.5 turns and then back in until idle settles.


Thanks for the zoomed in shot! That clarifies a lot.

Work in Progress:
http://www.feather.us/2006/09/01/hobbies/boating/moomba-adjusting-the-bleed-screws/

[iaonbb]

Excellent write-up Wolf! Makes me wonder though...Assuming I was running rich before, and I turned mine about a 1/2 turn out from their original seting , wouldn't I be running richer? Hmmmmnnn....Could it be the other way around?

Again, nice job!!!
MDB

[Wolf-]

Originally posted by iaonbb


Excellent write-up Wolf! Makes me wonder though...Assuming I was running rich before, and I turned mine about a 1/2 turn out from their original seting , wouldn't I be running richer? Hmmmmnnn....Could it be the other way around?

Again, nice job!!!
MDB

"Normally" in is lean and out is rich. /me ponders.
I'll let you know tomorrow. Going to look for my vacuum guage tonight. Then you can "see" your engine wheezing.

Too lean and too rich sound very similar in an engine.
Lets say you are running lean. You turn out past the optimal point (the sweet spot) and you are now too rich. She will cough, sputter, choke.

Where is our Indmar expert?

[iaonbb]

Forgot to mention...my operating temp also dropped slightly...not sure if this is related to the adustment, break-in, or both..worth mentioning. I might have to try turning them in more next time and see what that does? It's running so good now I don't wanna mess with it though...if it ain't broke...curious though

[Wolf-]

Originally posted by iaonbb

Forgot to mention...my operating temp also dropped slightly...not sure if this is related to the adustment, break-in, or both..worth mentioning. I might have to try turning them in more next time and see what that does? It's running so good now I don't wanna mess with it though...if it ain't broke...curious though

I don't know about the temps. I had to tear my thermostat out on vacation at hour 12-13. It seized up and wouldn't let anything through.

I'm looking forward to tomorrow. Got the video camera cables back so will be able to get those video clips from the tower mount someone asked for like 4 weeks ago. Got the wake tuned w/ #440lb under the seat and about #300 up towards the bow. Was landing in the flats all last Saturday. Felt really good, well, other than taking a kneeboard in the face, a nice black eye, and a 3 day headache.

[iaonbb]

OUCH! I feel your pain! I took a face plant on Wed and bruised my sternum/lung/ribs/whatever it was, it still friggin' hurts like a mutha! Still having trouble breathing...Gotta' watch that toe-side edge, lol.

I've been running around 165 deg F and it's now around 160 or so..well within range but a smidge cooler. Wondered if that 's sign of too rich or too lean before...I'd guess too rich, because now it's purring like a kitten...

[carsondoc]

Wolf, Great job! This tweek has made a world of difference for me and my enjoyment of my boat. It can be a bit challenging to describe verbally and you really did a terrific job with this.