Full Narrative
I’m trying to help out a friend with his outboard. Nearly every part has been replaced or rebuilt except the motor itself. But it still wont run right. It’s been to every local outboard shop and mobile mechanic that will work on it. Nobody’s been able to figure it out. We’re at our wits end and need the help of the iBOATS community.
CDI
Before I started working on it it had the CDI replaced. The lower unit was also replaced with a an SEI remanufacture. The wiring of the CDI looks correct. I’ll touch on what I found with the lower unit shortly; I’d like to go in the order I troubleshooted.
Flywheel
The owner advised that a previous mechanic had, “epoxied the magnets on the fly wheel”; The motor would turn over and fire up but there were obvious problems with timing and it would quickly come to a clunking halt.
The owner didn’t have a lot of details about the magnets. He wasn’t sure if they’d come loose, completely off or why they needed to be epoxied.
I found the magnets had in fact been reattached, but the placement was off. So we bought a replacement.
Stator
The stator was in bad shape. Much of the resin had melted off and there were signs of some sort of impact. I only did a visual inspection. I did not test it. He already planned on replacing it for good measure and it was on its way.
I cleaned up the melted resin and inspected the timer base. It moves smoothly and freely without any signs and hesitation. I installed the new stator and flywheel. It fired up after that and the timing problems subsided. But it was still running very rough. I was able to keep it running long enough to set the idle timing. There were timing marks on TDC and 4 degree ATDC (factory spec idle). But the WOT mark at 18 degrees BTDC was missing. I manually confirmed the TDC mark was accurate and then set idle timing to spec.
Water Pump
After achieving an idle consistent idle, I noticed there was no stream from the tell-tail. There was little to no water coming out of the exhaust as well so we ordered a full water pump rebuild kit.
I noticed that the top seal was all stretched out. I also noticed a gap between the shaft and the top opening of the housing, maybe about a millimeter in size. The impeller was shredded. I fished out the loose chunks of rubber and flushed it out using the flush port. I haven’t pulled the water jacket or heads so I don’t know if I got everything.
As I pulled what remained of the impeller off of the driveshaft, it got stuck. I discovered the drive shaft was scored where it had come in contact with the water pump housing. And the bottom opening had been ground from a circle to an egg shape and a bur had formed. The wobbly shaft must have caused, or at least contributed, to the scoring I found. I did my best to sand it smooth and rebuilt the pump.
I advised the owner of the problem. He called SEI and they told him, “It’s good for a drive shaft to be wobbly”. I’m not the most seasoned marine mechanic, but I have rebuilt dozens of water pumps and never seen a drive shaft with that much play.
Link & Sync
With the motor being properly cooled from the pickup, I was able to do a link and sync and achieve a decent idle. But it would randomly stall. I noticed a miss when it was running and the miss seemed to cause, or contribute, to the stall. I started pulling spark plug wires until I isolated the miss to cylinder #4. With that plug wire pulled the motor seemed to smooth out and. The miss went away and it stalled less. I could even rev it a little but it was still running rough and occasionally stalled.
Carburetor Rebuild
Setting the miss on cylinder 4 aside, it felt like there was a fuel delivery issue. I pulled one carb and discovered a few problems; the gaskets were intact with no holes, tears or fatigue cracks, but some were partially collapsed where the channels are. I also found a lot of oil (in retrospect this should have led me straight to the VRO).
I’ve seen carbs in worse shape running better but I recommended we rebuild the carbs. We used all OEM kits with new floats, pins and seats. I was careful to set the floats parallel to the housing. I also visually inspected the bowl and manifold mating surfaces because I know these plastic OMC carbs are prone to warping. They looked fine so I reassembled them.
I inspected the fuel rail for leaks and then rebuilt it with brand new fuel lines and spring clamps. I also replaced all of the zip ties with spring clamps on every fuel line between the tank and the fuel pump with the exception of the main line which has screwed clamps.
Before reinstalling the carbs, rail and lines, I visually inspected the reed valves. They looked brand new. The intake manifold gasket looked brand new as well. I’ll bet they were both replaced as someone was chasing the problem I am.
With the carbs reinstalled, I was able to get a hard primer bulb. The motor fired right up and idled well enough to do another link & sync and reset the idle timing. I felt like it was ready for a water test & tune.
1st Water Test
Immediately before driving to the boat ramp, I started and idled the motor on muffs for 15 minutes. It only stalled once shortly after it started as it settled down to a lower idle. It was still smoking a lot more than it should but it was running well enough for a water test/tune.
In the water the motor that had started on the 1st key turn and idled well would barely even start. It would turn over and fire but then immediately stall. The only way I was able to keep it running was to bring the idle way up. After running for a while I was able to reduce the idle down low enough to safely shift into gear. So I took her out to see if I could throttle up.
She idled beautifully all the way through the no wake zone. But the moment I tried to throttle up she hesitated, sometimes backfired and stalled. It was also smoking really bad. I had the air fuel mixture set to 7 full tuns (the middle between factory spec 6-8). I adjusted up and down but could not find a setting that the motor liked better. I’ve since found she likes 6 ½ turns best.
Compression Check
Back on dry land, I wanted to make sure we’re working with a viable motor before proceeding. I know, this should have been done sooner. The results were not encouraging at 68-78 (only one was at 78). Based on the miss I’d seen I thought I might find lower compression on cylinder 4, but it was in line with the rest at 72. I can post pics of the results.
I’ve seen compression improve with use so, after advising the owner it may be due for a rebuild, I continued trying to get it running in the hopes that it would improve once we could get it to run at WOT and clean itself out.
Fuel Pump
Still convinced that I’m dealing with a fuel delivery issue, the next logical step was to inspect the VRO (I’ll bet most of you reading this arrived at that quicker than I did). Live and learn. And the carbs did show signs of needing a rebuild anyway.
I started by pulling just the oil pump, it looked fine. So I pulled the front off of the fuel pump and had an ah-ha moment. The rubber around the piston had two fatigue cracks, one about two 3 centimeters long. This has to be the source of the fuel delivery issue, excessive smoke and oil I found in the carbs and oil rich / gas lean state I was seeing.
We couldn’t find a full rebuild kit that included the diaphragm so we ordered the only thing we could find… a piston rebuild kit. I was so sure I’d finally found the problem I didn’t even bother pulling the pump and inspecting the diaphragm. I rebuilt the piston replacing the seal and o-rings and reassembled the VRO. I was able to achieve a rock hard primer bulb. You can literally stand on the damn thing. And it stays hard with the motor running… like a teenager on Cialis.
2nd Water Test
There was no doubt in my mind that we’d found and fixed the fuel delivery issue. I was 100% convinced that the motor could be water tuned and the WOT timing set. So I invited the owner out on the water to help. I was so excited to see his reaction when it ran well for him for the very first time since he’s owned it. And flabbergasted when it did the exact same thing as it had on the first water test. I couldn’t even get it to start and stay running without cranking the idle way up. I found an idle that minimized stalling and still allowed us to shift, so we pulled away from the dock. It barely made it out of the no wake zone before stalling. Then I couldn’t even get it to idle again, much less throttle up.
I don’t know what to try next. Do I back track to double check my work? I pulled two of the carbs to adjust the floats and they looked perfect. I haven’t pulled the fuel pump back apart because I know it’s pumping well.
I apologize for the long post. I tried to list everything without being verbose. I failed miserably. If you made it this far, I thank you very much. I appreciate any help you’re inclined to offer.
