1998 Yamaha 9.9ELRX won't rev up past idle?

[JimEd B]

Afternoon,

Just picked up a new to me 1998 Yamaha T9.9ELRX outboard (along with the rest of the boat.) Looks to have had very gentle use.

Engine ran great when I bought the boat last month. Its been sitting since then, as I've been sorting out the Merc outdrive (yikes!). Big motor runs and shifts, so was hoping to do a quick service on the yamaha and hit the water.

No dice. On the muffs, the thing starts easy as pie. Idles real well, pees like it should, etc.

But any attempt to throttle up, including but not limited to "fast idle," and the thing just starts chugging hard. It doesn't die, it just bogs down, and sounds bit like its maybe misfiring? The little engine that couldn't. Engine sort of twitches a bit, and its really chugging low and slow. RPMs sound like they decrease and become inconsistent when you give it any throttle at all.

I went through the likely suspects. Fuel is flowing, ran it off the bottle on some crystal clear ethanol free. I cleaned the carb and plugs as PO's fuel looked like half brewed sweet tea.

It has spark, as it idles like a top. Plugs are heat range 4 and should be a 6, so will get those swapped out, but those are the plugs that were in it when I ran it before buying the thing and it revved up fine then.

Anyway, been looking around, and can't find much on this particular issue. Figured I'd ask around on here and see if this is a common condition, and if anyone has any other components to check?

I'd rather not just throw parts at the thing until something works.Thinking maybe something with that electric wax needle valve job bolted to the carb? Not really sure how to test that thing.

What y'all got? Heard it before? Halibut season opens tomorrow and I'm landlocked..... bummer.

Thanks,

 

[JimEd B]

Update:

Got it idling, and realized that there is no power to the Prime Start unit.

Neutral terminal has continuity to negative post on starter. Jumped power from positive post on starter to the PrimeStart positive side, full 12 volts coming out the negative side. Device definitely had power, and felt like it warmed up a bit, but no effect on the way the engine would run.

I also checked to see if the motor was sending power back to the battery, which it does not appear to be doing. Do these engines send a charge back to the batter?

Wondering if this is potentially an electrical issue more than a fuel issue. It has spark, and fuel, and air. So something is out of proportion somewhere.

I see that the power and neutral both go straight up to the coils under the flywheel, but I didn't have time today to get the flywheel off and see what lives up there.

I'm just learning these engines as I go here, so forgive me.

Any thoughts?

Would love to get my hands of a factory service manual if one exists. Anyone know where to find that?

Thanks,

 

[JimEd B]

Ran 12v to the electrothermal valve. It extends. Motor still running rich.

 

[99yam40]

All I have is make sure the fuel pumps are in good shape and not leaking into the crankcase, and make sure the timing is advancing as it should

 

[JimEd B]

Yeah, grabbed a manual. So far all I've been able to do is verify that certain parts were working correctly.

Fuel pump tests OK. Electro thermal tests OK.

I put in new plugs, correct heat range, and that made no difference.

Can't check valve heater coil resistance because I don't know the internal resistance of my multi-meter, and its less than 1 ohm. I don't have any loose known resistors around to measure my meter with, and I doubt that the coil would have gone bad.

Everything is pointing to tearing apart the carb again, but who knows. It really didn't look that bad, its not leaking, float isn't water logged. This particular set of conditions is not really identified in the manual.

I don't understand how it would idle fine, then misfire when you give it the gas. It doesn't stall out, it just chugs and slows down. Then when you let off the gas it wants to die. Getting some white / grey / blue smoke right at start up.

 

[99yam40]

do you have a timing light to see if timing is in spec and advancing as it should?

correct compression, spark, timing, and fuel to air ratio are needed to run properly

 

[JimEd B]

I do not. Apparently I would also need some tachometer attachment.

From my understanding, the book wants the engine running at 1500 rpm for testing. I don't think I can get it up that far as is, and could probably replace the CDI unit for close to the price of those two tools anyway. I believe its an electronically controlled timing system, so it either works or it doesn't. No adjusting. Is that correct?

I'm going to borrow a pressure tester tomorrow to make sure compression is good. Will tear carb down again as well and make sure I didn't miss anything.

If that doesn't get the job done, and compression checks good, I'm going to start throwing parts at it. I hate that approach, but usually either cheaper or faster than taking it to the shop (closest decent shop to me is 40 mins away, but FedEx delivers). Blackmouth / Halibut season is already in progress, Spot Prawn is coming up, and I just want this thing running.

Also, this boat is destined to fish 15 miles out in the salt, so new (good quality) parts are never really a bad thing. The kicker motor is not just for trolling, its also my number one life line.