Idle speed adjustment question

[vissertrades]

Hi, I've got a '95 50 Hp looper and I'm trying to get her to idle down to 800 rpm consistanly. I'm not having much luck. I have the Factory Service Manual and have followed the "sync & link" to the "T". Both idle mixture screws 2-1/2 out to start. Idled down to 800 rpm in lake and adjusted timing (idle speed screw as they call it) to 1ATDC. Idle speed seems to be controlled by mixture screws NOT the idle screw which adjusts timeing. Motor is smoothest with idle mixture screws at 2 out which in turn makes the idle 900 rpm. Do I have a problem or what? Everything else is perfect but this idle speed issue!

 

[Joe Reeves]

Re: Idle speed adjustment question

Piet.... Adjust the carburetors as follows, then use the mechanical idle stop adjustment screw to set the idle rpm.<br /><br />(Carburetor Adjustment - Single S/S Adjustable Needle Valve)<br /><br />Initial setting is: Slow speed = seat gently, then open 1-1/2 turns. (All carbs at the same time)<br /><br />(On the following adjustment, finish one carb before going on to the next one, then double check the adjustments).<br /><br />Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.<br /> <br />Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting. <br /><br />When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[vissertrades]

Re: Idle speed adjustment question

Joe, thank you for taking the time to reply! I'll take your advise but have a few questions:<br /><br />1. Make adjustments in forward while in water, correct?<br />2. What about timing, as the idle stop screw moves the spark control lever, do I need to be concerned about 1ATDC+/-1 at 800 rpm?<br />3. Once idle is adjusted, having moved the spark control lever (via idle stop) do I need to verify 19 BTDC max advance?<br />4. I have the Factory OMC Service Manual, why isn't your adjustment method listed?<br />5. Should I target 800 rpm as slowest idle?<br /><br />Thanks in advance!

 

[Joe Reeves]

Re: Idle speed adjustment question

You asked:<br /><br />1. Make adjustments in forward while in water, correct? = (No, in neutral. Makes no difference whether in water or on a flushette)<br /><br />2. What about timing, as the idle stop screw moves the spark control lever, do I need to be concerned about 1ATDC+/-1 at 800 rpm? = (Not unless you've changed the factory setting)<br /><br />3. Once idle is adjusted, having moved the spark control lever (via idle stop) do I need to verify 19 BTDC max advance? = (Again, not unless you've changed the factory setting)<br /><br />4. I have the Factory OMC Service Manual, why isn't your adjustment method listed? = (It may be but worded differently)<br /><br />5. Should I target 800 rpm as slowest idle? = (Whatever the manual calls for)<br /><br />EDIT: 09/13/03 - 10:41am<br /><br />If adjusting the idle on a flushette, set the idle to 1000 rpm if a 20" shaft engine, 1200 rpm if a 25" shaft engine.

 

[vissertrades]

Re: Idle speed adjustment question

UPDATE: I tried the adjustment method that Joe suggested and this was the result.<br /><br />1. Motor would NOT run with S/S needles at 1-1/2 turns out. Motor needed a minimum of 2 turns.<br /><br />2. Idle speed screw lowers idle speed but does it by changing timing. I got it to idle down to 800 rpm on the water in forward. Idle was smooth as silk, but when I checked timing it was about 6 ATDC. Spec at idle is 1 ATDC+/-1. I'm not sure what's going on but I set idle timing to 2 ATDC (most retarded while being in spec) and idle speed is now 900 rpm in forward on the water.<br />3. S/S adjustment was best at 2 out.<br /><br />Leave it or do I have a real problem that dealer need to address?<br /><br />Thanks

 

[vissertrades]

Re: Idle speed adjustment question

Could a partially plugged fuel filter cause this? Idle speed screws set at 2 out, any further in causes motor to hard/no start and die at 1-1/2. At 2-1/2 out motor smokes and idles rough. Any help, Joe?<br /><br />Thanks!