Another problem...I give up!

[poolecw]

Well guys, I spent most of Friday evening and night taking the carbs apart and cleaning. I'm no expert but I didn't find anything that would lead me to believe that my issue is due to dirty carbs. They all look very clean and I saw no varnish or gunk. I kinda wished that they were dirty...no I'm back to the drawing board.

Just to recap:
Spark plugs are brand new. I used NKG part number BUHXW-1
During last week's trip to the lake, the motor would not get up on plane. Lack of power. Also, warning horn started going off as I was running the boat.
Idle was smooth but would shake when trying to get up on plane.

Made two trips to lake in early summer and the boat ran like a champ . No problems what so ever (this was after sitting up for several years). On third trip, motor would not idle except using fast idle throttle setting. I used Seafoam and it fixed the idling issue. Forth trip to the lake, idled fine but would shut off when putting into gear. This led me to change out spark plugs.

I think my next steps will be to drain all the gas and replace. Fresh gas was already in there but I just want to eliminate that possibility. I may also try to clean out the oil tank and oil line leading up to the VRO. I don't think this is an issue but the oil in the tank is a couple years old. I will then try to test the spark on each plug.

By the way, I did a compression test and all cylinders were between 83-85 psi.

 

[fireman57]

fresh fuel and known good oil are musts anymore. I would do the spark test as per Joe Reeves method. Make sure the spark is bright blue. If you do take it out and it still wants to bog bump the primer solenoid (choke) and see if it picks up and goes. Trying to determine if it is fuel or spark problem. AGain, you could have an air leak in a gas line fitting. The warning horn that was going off, was it the overheat alarm? I did have a 70hp that the wire was shorting out. Unhooked it and boat ran fine. Had to trace down the short and fixed it but it isolated the problem.

 

[fireman57]

one more thing, make sure you use the correct champion plug in these engines. They were literally built around them and make sure they are gapped correctly.

 

[poolecw]

The warning horn was continuous so I believe it was the overheat indicator. The NKG plugs that I put in there are not the style that are gapped. The end is Blount. Going to test for spark, chang fuel & oil, take it back for test. Plugs seem to too cool so I will look for the champion plugs.

 

[Joe Reeves]

Get rid of those Jap surface gap plugs and install the recommended Champion QL77JC4 plugs, gapping them at either .040 (original recommended gap) or the later revised gap of .030 which came into being in the late 1990's. One gap or the other will provide improved performance either at idle or full throttle (it varies from engine to engine).

Surface gap plugs regardless of their designated heat range are cold running plugs and prone to fouling.

The warning horn sounding off as a constant steady beeeeeeeeeeep, on that model engine can be either a indication of Overheating... OR... a indication of a fuel restriction.

Questions:
1 - Does the engine appear to be running hot?
2 - Does the fuel primer bulb have a tendency to be drawn flat when the horn sounds?
3 - Did you manually clean the high speed jets with a piece of single strand steel wire as solvent doesn't do that job properly?

 

[emdsapmgr]

The Bombardier Parts and Accessories Guide recommended spark plugs for that V6 engine are: Champion UL77V, the tipless plugs. From 1976 through 1987. That's what I run in all of my early V6 crossflows. Never had any issues with them in any of my V6 engines.

 

[poolecw]

I cleaned the jets using some thin wire. They all looked fine. I don't know why the horn was going off. It did not appear to be running hot and the fuel primer bulb was fine. I checked that first thing.

This morning, I replaced the NKG's with the Champions and I changed out the gas and the oil. I also started it up for the first time since cleaning the carbs. It took a lot of choking and running at fast idle to get it to not shut off on me. I had to keep working the choke for a few minutes before it finally settled in and would idle. One thing, it seems to be idling at higher rpms now.

I'll make the hour trip to the lake tomorrow after church for a test run.

 

[Joe Reeves]

The high speed jets I speak of (2 to a carb) are located way in back of the drain screw plugs of the float chambers... horizontly in the center bottom portion of the float chambers. Are these the ones you manually cleaned?

 

[fireman57]

Idling at higher rpms to me indicates that you have been chasing a fuel problem. Glad you went to the champion spark plugs. Please stay with them. Like Joe said, this jet is behind the drain plug in the carbs. You can make a special screwdriver to get them out by grinding down a small screwdriver. Don't remember the tolerance but don't just dig in there with a regular screwdriver. Do a search on here so you get it to the right tolerance. Also, when you do get it out there and it bogs, just bump you primer solenoid and see if it does pick up and go. Still looking at a fuel delivery problem from here.

 

[poolecw]

Yes, I didn't have that special "OMC TOOL" so I ground down the point of a flat head screwdriver in order to get them out. I have a 1984 OMC V4 and V6 Service manual that I used to go by to disassemble the carbs.

 

[poolecw]

Well, the trip was unsuccessful. The motor would not idle without having to use the throttle. It idled just fine at higher RPMs. I think it needs adjusting to give it more RPMs during idle. I think this may have something to do with the linkage connecting the carbs.

Also, while sitting on the ramp working on keeping it to idle, the warning horn went off. I'm 100% sure that the motor didn't get too hot. Must be sounding due to a fuel restriction but I don't find anything.

 

[emdsapmgr]

Even if the engine shows it's running cool, it may think it's overheating. So, try disconnecting the two head temp switches an see if the horn silences. One of them could be shorting to ground, inadvertently causing the hot horn. Same test for the fuel vacuum switch.

 

[poolecw]

SUCCESS!

All the old motor needed was a return trip to my dad's. He went over it with a fine tooth comb and found a few things (mostly from my fumbling around with it). First, he notices all three carbs were not synced up. Then he found the timer advance had become disconnected. After giving it a test run in his 12 acre lake, we pulled the plugs and found the bottom left and bottom right plugs were not burning. So he pulled the bottom carb and found the jets were clogged. So we cleaned it and the other two carbs. After putting the carbs back on and syncing up, we put it back in the pond. It ran like it was fresh out of the OMC factory in Calhoun, GA.

Thanks guys for putting up with all my questions.