V-4 OMC crossflow idle tuning

[Georgie]

Evenin' Gents -

To those who've worked on these engines or have suggestions for this frustrating final step, please throw them my way:

I've been trying to dial in my father's recently rebuilt 1990 Johnson 110 and can't figure out for the life of me why we can't get the engine to stop stalling when motoring at idle    (it runs great throughout the rest of the throttle range).  I've rebuilt 4 of these engines already, so I've made all the basic adjustments, but he doesn't have a working tach which makes things a bit more difficult than they should be to set timing (he also doesn't have a timing light).   Simply put, the idle RPM's are too low, but the idle adjust screw is already bottomed out, and I've already had him advance the timing just a hair, but afraid to go any further.  He's also running stock 110 jets and carbs as well as pistons.  I compared the alignment of the entire throttle/carb linkage to the alignment on my engine (same generation) and his 110 is already slightly advanced compared to mine (both throttle and timing), yet mine idles around 900 rpms without stalling and I'd guess his is probably trying to run as low as 4 or 5 hundred rpms and just can't quite hang on to stay running.

To try and refute fuel restrictions as a potential issue I had him pull his plugs the other day and they're all pretty wet (not dry, white, or ashy) so the motor seems to be getting plenty of fuel.  However, I did use a mix of old parts when I remanufactured and installed his fuel pump, so I wonder if the diaphragm could be bad and the engine's only getting enough fuel when the engine's running at speed and creating a stronger vacuum?

I'm out of ideas at this point.  Throw me whatever pops in your heads PLEASE!  Picture below.

[slvrlng]

Maybe low speed jets are clogged.

Did you link and synch?

[Georgie]

Carbs and jets were cleaned with B-12 chemtool, plugs appear to be getting even amounts of fuel, and carbs are synched and tightly linked to timing linkage, but not sure if the timing advance is perfect.

[fitz73222]

Georgie,

You have to establish base idle timing with a timing light before you can proceed with anything else. Timing lights are cheap; go get one at the auto parts store. The timing settings should be on the front of the air box cover. You can't compare the position of of the linkage between your motor and this one. That's why the timing is adjustable mainly do to slight differences in stator tolerances and running production changes in system components. The timing can be set at cranking speed without the engine running; you need a fully charged battery to do this. I recommend you do this with a flush attachment hooked up with water flowing to avoid damaging the pump or do this in the water. Take the spark plugs out, ground them to the block and hook the timing light up to #1 spark plug wire making sure the plug is grounded. With the plugs out, it will make sure you obtain the minimum 300 rpm at cranking speed to adjust the timing. Point the timing light at the timing pointer; 0 timing mark on the flywheel is TDC (top dead center) all numbers to the left of 0 are (advance) or BTDC, all numbers the right of 0 are (retard) or ATDC, most engines run poorly if at all at ATDC Also check your max advance timing. You will need to disconnect the throttle cable at the engine and open the throttle wide open using the timing arm to fully advance the throttle and have someone crank the engine or you can jump the solenoid. If you jump the solenoid, make sure the keyswitch is on so you get fire.   Once you get the engine timed, put the plugs back in and see how it runs. If she fires up and races back off your idle speed screw until it starts to run at a reasonable idle speed. You have no low speed mixture screws on this engine if memory serves so that eliminates that variable. Try doing this first and let me know the results. Next we'll work on throttle synchronization and phasing in the throttle butterfly positions. I apologize if you already know how to do this; I'm just trying to establish the baseline.

[Georgie]

Thanks Fitz - I kinda figured he wouldn't be able to go any further without a timing light, so he's been sent on a shopping mission to buy more "toys".   Once we set timing per manual, I'll post back if we still can't get the adjustments right.

btw - Happy B-day!!

[Georgie]

Looks like timing was retarded.  timing light showed 25 rather than 28 degree advance timing.    Have reset per factory spec and will report results once tested in water.  Should solve the idle issues too.  Fingers crossed.  Thanks for the assistance guys.

[saltfly]

When it was rebuilt, do you have it bored, and  if so how much over?  When you bore a cylinder by .010 or more, you have to resize the jets. So motors will run but lean. other will stall.

[Georgie]

Salt,

I just had the cylinders honed true.  Engine had overheaded and locked up, pretty sure b/c VRO failed.  I was able to free it without any major damage, clean it up, and re-use pretty much everything after having it honed and installing new rings.  Just running on premix instead of VRO now.  Obviously honing takes a tiny bit of meat outta the sleeves and may drop compression a hair b/c the seal is not quite as tight as original, but not enough of a difference for me to worry about with these old clunkers, so I'm still running stock jets in the carbs.  The timing adjustment seems to have solved the issue, but we'll know for sure when he puts her in the water.  We're watching the spark plugs like a hawk to keep an eye on combustion mixture as she's broken-in.  Thanks for the pointer!

[Dhadley]

The wide open timing stop has no effect on idle. Make sure your 28* is under a load at or close to wot. You can use the -4* set up procedure if you want to set it at lower rpm.

[Georgie]

DHadley,

Do you have a login over on iboats.com forums?  If so, I think you've given me good advice over there in the past!    I may need a bit more 'splainin' as far as your comment is concerned though.  We set timing advance to 28 degrees using pretty much the exact procedure Fitz described earlier.  Removed and grounded the plugs, throttle at max forward (even though the timing position doesn't change in the top 1/4 of the throttle range), and timing light rigged to #1 plug wire.  One guy turns ignition key while other reads the timing at the pointer.  We did find that the timing at max throttle was previously retarded by 3 degrees (25 instead of factory recommended 28 degrees) which likely explains the entire problem.  I know increasing timing advance from 25-28 will also correspondingly advance the idle timing a little and should remedy the extremely low rpm idle issues, but we haven't been able to get her back in the water yet and put backpressure on the exhaust to verify.  Which wide open timing "stop" are you referring to?    If the 28 degree setting is simply a matter of matching the ignition spark to a certain position of the flywheel/crank, then why would load affect the accuracy of the setting?  Where is this 4 degree procedure you speak of   It might be very useful as a cross-check.

Thanks!!

[Dhadley]

Setting the wot timing that way is fine but you'll be looking for 24* rather than 28*. When you run the motor under a load the motor will automatically pick up the extra 4*. Very very seldom do we see any difference between 28* and 26*. Those motors do not like timing over 28*, they tend to burn pistons at over 28* timing (speaking of recreational motors).

Normally the idle stop and the adjustment on the throttle cable are pretty much centered when everything is set right and the motor is running as it should. Make sure the cam follower is not touching the roller at dead idle. Disconnect the throttle cable to set the sync & link as per your factory service manual. Then reconnect the throttle cable.

[Georgie]

Ok - so it sounds like I took a borderline bad but still functional setting at 25 degree advance, and made it even worse then by advancing to what I thought was correct at 28 degrees.... great.

Now I'm even more at a loss for the low idle RPM's b/c resetting the timing to 24 degrees at WOT will slow it down even more.

[Georgie]

Took the "plunge" (literally) and timed her on the submerged trailer at the ramp in forward gear and at full timing advance.  Sure as chit she read 32 degrees just like you advised DHadley.     Dialed back down to 28 and purring like a kitten.    Thanks for the advice guys.  Now we can be confident she won't detonate and that timing is optimal.  Will see how the idle does over the next few trips, but so far it seems to be slighly improved so she's not stalling when shifting gears.  

[kraw2]

Thank you all for the information. I'm just about ready to do this on a '98 115 SPL.