Cannot figure out a lean running 93 140hp

[jeffj254]

Re: Cannot figure out a lean running 93 140hp

I checked the timing last time it was in the water and I believe it was correct. It's tough to do though as the motor doesn't really run well enough to get a good reading, and from what the service manual tells me it needs to be under it's own power in the water to check properly.

If it wasn't releasing the quikstart timing advance, wouldn't that mean a problem in the power pack?

 

[jeffj254]

Re: Cannot figure out a lean running 93 140hp

It's been a while since I've posted, there's a video at the bottom with the current state of the motor. I've been slowly working on the motor piece by piece, but I'm just as stumped as ever. Here's what I've done:

took apart entire top end of motor from carbs down to crankcase. Replaced all gaskets including intake manifold, reed box gaskets, throttle body gaskets. Rebuilt all 4 carbs again. Replaced water pump, replaced thermostats.

The reed boxes looked perfect. No light showing through, no cracks, nothing broken. The intake manifold looked fine, perfectly flat, existing gaskets lookd fine too. The carbs looked OK. I found one with a bad gasket on the upper body to throttle body connection. I'm having a hell of a time getting them to seal perfectly though. Fuel still seems to seep out from the bowl gasket. I really don't like these plastic carbs.

Anyway, after all of this, I just started it again for the first time in 2 years. It runs almost exactly the same. Won't idle, sounds like 2 cylinders are out. The one thing I do notice is that the starboard cylinder bank is significantly warmer than the port cylinder bank. Warm enough that it would burn my fingers if I held them against the thermostat cover. This seems odd to me, but I'm not sure if it's due to inadequate cooling, or those cylinders running lean and getting too hot.

I've recorded a video of the motor trying to run, maybe it will help. Any tips are much appreciated.

http://www.youtube.com/watch?v=PeyIG9vpIjM

 

[jeffj254]

Re: Cannot figure out a lean running 93 140hp

Another update:

Spent some more time on it today. I bought a 3 gallon portable tank and filled it with 50:1 premix. I wanted to be positive it was getting enough oil and I can rule out the tank in the boat, water filter, old gas, etc. Still ran pretty much the same. Still didn't smoke much. This is the first 2 stroke outboard I've seen that doesn't smoke when it's cold.

I also bought an infrared thermometer. After running the motor for a while I shut down and checked the temps on each of the thermostat covers. Port side was 115-120, starboard side was 160. This seems odd to me, not sure what it means. My service manual says it should be between 120-150, but it seems odd that each side would be so different.

While it was running I tried spraying fuel down the carb throats. The starboard side of the engine clearly isn't running right. Spraying down the carbs on that side would cause it to perk up a bit and run better, while spraying in the port carbs would immediately make the engine stumble. I tried spraying at the plates on the sides of the carbs and at the throttle body connections, but this didn't seem to do anything.

I'm really lost at this point. It seems like the starboard side isn't getting enough fuel, but when I pulled the plugs right after running it they were covered in carbon and seemed somewhat wet(they're fairly new). I guess the head gasket could only affect that side of the motor, but compression is fine, so it's not obviously bad. Both thermostats are brand new, as is the water pump.

Long story short: Motor won't idle, starboard side hotter than port, extra fuel seems to help, plugs look slightly fouled.

 

[cdoliver]

Re: Cannot figure out a lean running 93 140hp

did you remove the jets when you rebuilt carbs? you might have to remove the heads to see if you have gunk built up in the water passageways. also inspect replace the rubber water deflectors. I don't think that motor is should to be run without the air box cover on. does it still sneeze when you spray premix in the carbs? Have we checked spark yet? The video sounds like its down a cylinder or 2. are all of the carb butterflies closed at idle position?

 

[jeffj254]

Re: Cannot figure out a lean running 93 140hp

I pulled one of the jets out when I did the carbs as I was replacing the entire bowl section, it was spotless. I didn't pull the others.

I've been thinking about pulling the starboard head. Is there anything I can do to check for a clogged coolant passage other than just looking at the water jacket?

I don't normally run the motor without the airbox on, but how else do you decarb it or spray anything down the carb throats? Oddly when running without the airbox it spits fuel through the air bleeds, seems odd.

Spark is definitely good when the engine is revved, I'm not too sure how to check at idle. I don't have one of those tester things the service manual mentions. I just bought 4 new spark plugs today, so I'll be replacing those again.

Could the powerpack be bad for just one side of the engine? I'm wondering if the timing is all screwed up on just the starboard side.

 

[Dhadley]

Re: Cannot figure out a lean running 93 140hp

Keep in mind that the starboard carbs feed the port bank and vise-versa. The block uses an X pattern front half.

 

[jeffj254]

Re: Cannot figure out a lean running 93 140hp

I didn't realize that, thanks for pointing it out.

So that would mean the starboard side seems to be running normally while the port side isn't. Which means my temperature readings really get confusing. Perhaps the hot temp on the starboard side is normal while the cool temp on the port side indicates constant missing from those cylinders?

Should I even be looking at the temps at this point then?

 

[cdoliver]

Re: Cannot figure out a lean running 93 140hp

Id take a look at the starbord side carbs again. If you spray premix in those carbs and it picks up, you either have a air leak in the line somewhere or a clogged jet. less fuel from the starbord carbs means there is less burning going on in the port cylinders hence the lower temps.

 

[jeffj254]

Re: Cannot figure out a lean running 93 140hp

I've been into the carbs 3 times now, and from the very beginning they've been absolutely spotless. No varnish, no dirt, they look perfect.

The motor runs fine at higher RPMs, if I rev it hard with the air cover off I can see fuel getting sucked up out of the main jets in each carb.

Is there another jet or orifice somewhere that fuel goes through at idle? I've sprayed out every passage on every carb 3 times now and I can't find anything that seems in any way clogged.

The recircs are all brand new, and should be fine, but I can't find a syringe and tubing to actually do the test on them. That's pretty much the last thing I'm wondering about, if the recirc pathway is somehow plugged up on the port cylinders.