'89 Yam 150ETXF issues not firing (but has spark) on bottom 4 cylinders?

[StamfordRob]

All.

I spent the season chasing what was thought of as a fuel issue. Everyone that I bumped into mentioned fuel fuel fuel but at this point I have something odd and I think its leading towards ignition unless I can get recommendations of new places to look.

The motor is a 1989 v6 150ETXF and it started as an issue where the motor didnt go over 3k. It ran as if it was hitting a governor. At the same time I needed to replace my fuel tank so I started following the lines towards the motor. New tank, new lines, 2 new pumps, broke down carbs and rebuilt them. Reran motor on pony tank and all issues still the same after motor work. I can dump the carbs and see that all bowls are full of fuel. Did pressure check and have 120lbs on each cylinder. When I pull the plug boots off the top 2 cylinders give an expected lob to the motor. When I pull any of the bottom 4 cylinders the motor doesnt flinch but I hear spark happening. I sprayed cleaner into the bottom 4 throats and nothing happened. The motor didnt jump or change at all. Every few rotations the motor has a miss and a burp, but nothing steady.

note..I also changed coils around and nothing changed. I'm at a loss.

At this point I am lost on where to look. Any ideas are appreciated. I would like to salvage some of my season in CT and God knows my wife would love her parking space back.

Thanks.

Rob

 

[cgvirginia]

I have similar issues with mine. I would get a inline spark tester and check all your plugs. They are cheap and auto zone has them. If you don't have spark check your boot, wire, coils and go from there. swap known good ones with questionable ones.

 

[StamfordRob]

Last night I looked at it again and I have spark on all cylinders and even moved coils around and no change. Its very odd but as I move down the cylinders I get less reaction when I pull off the boots. I do see some reaction on the lower cylinders but not like when I pull the boots off the top 2 cylinders. Big difference. I even swapped plugs and double checked gaps but no change. I increased the idle needles on the bottom cylinders from 1 5/8 to 2 turns and still no change (will return back to 1 5/8 tonight). I see that I am getting fuel to all cylinders though.

 

[Doh]

I would call a carb problem. The Idle Needles that you talk about are actually Air Screws, so turning them out makes the engine Leaner, screwing them in will make it Idle richer.

 

[StamfordRob]

OK. I have been tied up this summer and just wasted my season this year. But the boat is in the water and I am back to the problem with a month left before I have to pull it out for the season.

Before it went in i pulled the carbs and rebuilt them again. They looked just as clean as they did with the last carb cleanup. I have new needles, floats, gaskets, etc. I still have the issue with the bottom 4 plugs not giving a powerful spark. Matter of fact the bottom 2 barely have enough charge to light. I can hear the spark but its so low I doubt its firing the cylinder. When I pull the top 2 boots the sparks is strong and snaps really clear.

I ran it today and the top 2 plugs looked good and the lower down the motor the wetter the plugs got.

Am I looking at a power pack?

** The screws. So I know what I am talking about. The spec manual called them Pilot screws ( i called these idle screws). Are these the Air screws?

 

[StamfordRob]

Is there a way to measure the voltage at the boot? I'd like to see if I am getting full voltage at the plug. Maybe that will help resolve my issue.

 

[99yam40]

they make KV testers that read 1000s of volts
But most use a spark tester to just see if spark can jump a 7/16" gap

You also measure the input into the coils with the proper test equipment.
DVA adapter with DMV will work

 

[StamfordRob]

OK. So I looked back at the motor today and found that the spark is good on all cylinders. Odd I think it sounded better today than before but I will go on the fact that it jumped the 7/16 gap with ease.

But today I found that it was pouring fuel from the throats so something must have blocked or was sticking my float. I tore down the carb and found debris in the seat. I removed it and doubled checked the float height again (specs listed 15.5-16.5mm from gasket). All is good. But when I glanced over at my pilot numbers again I saw that my specs are listed at 1-1 1/4 so I was way over at 1 5/8. I believe that I used the same turns that I removed it at and not from the manual. So be it I stand corrected.. Good. BUT. I also notice that there was a note on that carb spec that stated that the 1-1 1/4 was for most 150 models other than a 'P" model. How can I identify this carb because they have the oddest specs (1 1/4-1 3/4 PORT, 3/4-1 1/4 Starboard). I attached a pic of my numbers but was told that the P on the end is not part of the model but I want to check on it as its a big coincidence that I have a P on the carb and I could have a motor that is 50% rich.

I assumed my carb model was 6G405 (left number). Can anyone identify the number on the right (8502P).?

** I added the specs and note 11 that shows the 'P" model note. Please review for me.

Any help identifying this would be great.

My outboard:
1989 Yamaha v6 150 ETXF.

Thanks...r