Connection between steering and rpms??

[Georgie]

Ok gents - need some suggestions as I've encountered a gremlin and can't for the life of me figure out the cause

My V4 johnnyrude crossflow is fluctuating approximately 250 rpms at (running slow speed in the channel at 1500) depending on which way i turn my steering wheel     Turn the wheel a couple turns to starboard, and she gains 250, turn back a few turns to port, and she drops those same 250.  I'm completely at a loss as to how steering could affect engine speed instantaneously like that since no parts of the actual steering assembly (arm, tube, cable, etc) actually enter the cowl.    

Things I do know:
1.  while the issue somehow may be fuel related, pretty sure it is NOT a pinched or kinked line b/c the engine rpms change immediately upon turning the wheel, but it would takes 30-60 seconds to burn though all the fuel in the carb bowls.
2.  the issue has nothing to do with any list in the hull.   To verify this I centered the steering and had my passengers switch sides of the boat changing the list from starboard to port and back, but saw no change in rpms.
3. aside from the rpm issue, she is also misfiring some (excessive unburned fuel exiting through exhaust  and wobbly at idle), so the two issues are likely somehow related.
4. all coils/plugs are currently firing (removing plug boots while running affects operation)

Commence brainstorming... I'm planning to run her after dark tonight to look for arcs in the ignition wiring and will post results.

[RickK]

I think it is the throttle cable somehow moving as you turn the motor side to side, which moves the throttle in the motor.

[Georgie]

Good point.  So focused on the other side of the engine I completely overlooked the most logical possibilty.     I'm gonna feel like a horse's behind if you're right. Talk about full-blown mental block.  Perhaps I should lay off the sauce til I figure this one out.  

[GoneFission]

I think it is the throttle cable somehow moving as you turn the motor side to side, which moves the throttle in the motor.

I'm with Rick, but there's also a chance a wire is intermittent and you are losing one cylinder when you turn at that speed.  At 1500 RPM, you would lose about 300-400 RPM with a single cylinder misfire.  Also, check the carb mounting bolts/nuts - you could be sucking air on one carb when the engine turns if the nuts are not tight.  

Good luck!

[Georgie]

OK - I'm throwing pride out the window for the sake of brainstorming.   :(

The steering/rpm connection appears to have just been a minor sync issue with the carbs.  The throttle cable was under a TINY bit more tension when turned to stbd and it pulled microscopically on the carb linkage.  Loosen flathead screw...adjust tension on carb linkage...tighten flathead screw...fixed.

HOWEVER -

I cannot figure out why she's still missing, but it seems like she's either not burning the fuel she gets well, or is getting way too much fuel.  

Symptoms:
-intermittent wobbling at all rpms (lower half of throttle range only b/c I'm on muffs in the yard)
-excessive smoking
-VERY obvious petroleum on the puddle under the engine
-fairly heavy black ooze drip behind the prop and down the skeg
-unsteady RPMs...fluctuates a few hundred rpms for a few seconds at a time (i.e. running at 1500 rpms for 8 secs, then slowly drops to 1200 rpms for 3-5 seconds...then wobbles and climbs up to 1600 rpms for a few secs, etc.)  I feel like this symptom is the key, but I can't for the life of me figure out why she's being inconsistent given all the things I've already checked (see below).

What I know/have done/haven't done:
-not a fuel issue related to the vent...it was GUSHING air last time I filled (last weekend - and therefore it's not an old fuel issue either)
-not a filter/separator issue...just replaced it a few weeks ago and every time I drain the bowl the fuel in the bottom is fine (no water or grit
-not a) anti-siphon issue b/c my primer bulb isn't flattening
-not a fuel pump issue b/c the primer bulb is always more than half full of fuel
-not a blown cylinder (verified compression two days ago)
-carb float needles look good under magnification (but I haven't replaced them)
-no clogged jets (cleaned and inspected each one)
-no observable arcing/grounding of ignition charges to the block when running after dark
-pretty sure I don't have a vacuum leak in the fuel hosing b/c I've gone over it with a fine toothed comb and tightened/checked all my hose clamps/tie wraps
-all cylinders are getting strong spark (removed boots during operation)
-not spark plugs (just swapped them in case one was randomly malfunctioning)
-can't feel any slop in the pistons so I'm pretty sure I haven't blown any crank/rod or wrist pin bearings
-Probably not the carbs in general (I've gone through the carbs twice just to verify all passages are clear and everything moves and is sealed properly)
-have NOT yet verified timing, but a timing issue is not likely b/c the engine was running fine a few weeks ago and I haven't adjusted anything nor has the linkage loosened.

Whatcha got for me Gents???  Fingers crossed!

[fitz73222]

Georgie,

Don't rule out a fuel pump issue. I've seen a ruptured diaphragm or sticky check valve cause fuel to get dumped back in through the pulse line and try to flood the engine or cause excessive fueling of the cylinder adjacent to where the pulse line connects to the block. I would have a look at the fuel pump diaphragm and look for small cracks, stretched or other abnormalities. They're cheap to rebuild. This condition can occur and have no adverse effect on a performance issue other than idle and midrange overfueling. Also incorrect float height or saturation of the float material from ethanol attack can effect their buoyancy and also cause overfueling. The floats can be weighed on a gram scale to check for saturation. For Merc's, they actually list the float weight so I'm sure it's available for OMC's.

[Georgie]

Two excellent suggestions.  Thanks Farley.    Will look into both.  Probably just gonna rebuild the fuel pump anyway b/c she's OOOOLD and has undoubtedly seen her share of ethanol!  Just never had a reason to do so til now.     You think excessive fuel in the cylinders could cause the rpm issue (kinda like intermittent flooding)?

[fitz73222]

Yep, overfueling can lead to all kinds of issues. That was one of the big reasons why a lot of older engines meet an early death. The engine cokes up, rings get stuck and that's when they catch on an exhaust port and its all over. The engine has to have about a 14-1 air fuel ratio to run right otherwise they run like crap. Too much fuel upsets that ratio and combustion doesn't work right anymore. The opposite is true when an engine is running lean, but it will destroy itself from heat but run great right before it bakes alive. I play with antique outboards and am a collector. All of those engines had adjustable high and low speed needle valves and you learn about mixture and how it affects running quality. I just got through putting together a '53 Mark 20 Merc that was a barn find. The engine loves to run lean on the high speed jet but you have to run it a 1/4 turn back to rich to keep it from destroying itself and there is a noticeable difference in performance between the lean and rich. So you compromise. When you take the purge line off see if it has oil or fuel dripping out of it. It should really be bone dry since it really should be just exchanging air pulses from piston motion and crankcase pressure changes. Hope it works!

[Georgie]

No luck!   :evil:

overhauled fuel pump w/new guts (sierra repair kit)
Replaced floats and needles w/spares from other carbs (carefully adjusted float heights/range and inspected needles with magnifier before re-sealing
replaced spark plugs
ran off auxiliary pre-mix tank  with two-week old fuel to make certain the fuel in my tank and filter weren't somehow bad.

Still runs rough at idle, rpms are unsteady, and excessive oil in the exhaust.

My fuel pump doesn't have the separate pulse tube, it mounts to the manifold and has a hole in the back that seats over the pulse opening (spacer gasket in between).

In essence, none of the above work changed anything in how she runs.  Any other ideas where I can look?    I'm completely at a loss.  Have been in and out of this dang engine so many times I'm not sure where else to go.  clogged vacuum lines?? stator/timer failing?? I don't want to tear her down if I don't have to, but it's getting close to that point b/c I don't feel safe taking the boat offshore with a known gremlin.  

I took a short video but I left my usb cable at the office so I won't be able to transfer it from my phone to my computer until tomorrow.

[fitz73222]

Ryan,

What year is your engine?

[Georgie]

'89 block, '82 carbs and ignition.

[fitz73222]

Have you taken this engine out and run WOT since you've done all this? She may be really loaded up and the flush in the driveway isn't going to get it. I guess it wouldn't hurt to check the bleed lines and make sure they're not clogged. Is this engine VRO?

[Georgie]

No.  Haven't been back out offshore since last outing when I noticed it running rough at trolling speed and when idling while we deep dropped on a few wrecks.  Cruised out at and back planing nicely at 25 knots.  Sounds great when on plane, she just sounds like chit when RPMs are below 1500-1800.  I run pre-mix through a 1982 OMC fuel pump.  No VRO.

[Georgie]

Sound quality sucks, but you can definitely hear the rpm issues in the last 15 seconds of the video.

http://www.youtube.com/watch?v=UzBWFygsxGE

Since I've checked all the things mentioned above, and since I've verified compression and spark to spec, I was going over components/systems related to fuel that I haven't verified yet....and had a VERY hopeful epiphany!   I wonder if my primer solenoid is bypassing fuel during operation thereby enriching the mixture and nearly flooding the cylinders?  easy to check and in principle could very much be the culprit.  Fingers crossed. Will check when I get home.

[fitz73222]

Sound quality sucks, but you can definitely hear the rpm issues in the last 15 seconds of the video.

http://www.youtube.com/watch?v=UzBWFygsxGE

She is loading up and trying to miss then recovers. This engine runs fine at 3000-5000 rpms?