1990 200 Yamaha problem

[i_build]

I ran a can of spray decarb through the carbs while running the engine, the directions ask that the engine then be shut off and started again after a period of sitting. When I started the engine it began to miss "hard" I imediately shut it off, and restarted it and it ran fine. <br /><br />It ran fine for a few all day trips, but now it started missing as it did during the decarb consistently. It starts missing at about 2500-3000 rpms which is not enough for me to plane. The weird thing is that if I shut the engine off, and start it and IMMEDIATELY got to WOT, it almost gets up to about 4500 rpms at a plane and then starts to miss dropping back down. Otherwise if I let the engine idle for a few seconds after starting then try to throttle up, it only gets to 2500 - 3000 rpms (without getting on a plane). I'm guessing fuel related, but I am open to suggestions / recommended tests. Thanks.<br /><br />

 

[i_build]

Re: 1990 200 Yamaha problem

Got it... Didn't think it would react as described above because of a failing battery, however in switching batteries (a problem I did not mention above), all symptoms went away. My battery recently refused to hold a charge overnight. <br /><br /> Could this battery issue really have been the root cause of the missing at high rpms?

 

[Ray Neudecker]

Re: 1990 200 Yamaha problem

Low battery voltage will cause the CDI to do weird things.

 

[i_build]

Re: 1990 200 Yamaha problem

Thanks Ray, but I think I may have spoken to quick. Drove across Tampa bay to Apollo beach at 30MPH... came back at 6MPH. <br /><br />Same thing... after getting across the bay, and shutting her down starting her again... when I throtle down she starts to miss hard. Even when I rev her up (which I don't like doing) in neutral... she's missing after about 2500 RPM. <br /><br />Would a bad coil pack cause an intermitent issue like this? It's just odd that it's an off and on issue. I assume if it were mechanical... it would be consistent. <br /><br />Also what's weird like I mentioned before, when experiencing the problem she reaches higher rpms without missing if I start and immediately throttle down versus letting her idle, but once she starts bucking, I have to bring the rpms down to about 2500rpm for her to run smooth again. <br /><br />Any suggestions would be greatly appreciated.

 

[rodbolt]

Re: 1990 200 Yamaha problem

sounds almost like an alarm signal is sending it into speed reduction. have you tested the audible horn lately ?

 

[Ray Neudecker]

Re: 1990 200 Yamaha problem

Many things can cause the symptons, from a fuel problem such as a needle sticking in a carb to bad ground connections on the coils or other electrical parts. Like Rodbolt, I would want to test the horn to make sure it wasn't going into a safety mode. Did you relace the plugs after decarboning? Have you changed the fuel filter? May be time for a complete going through of the fuel system.

 

[i_build]

Re: 1990 200 Yamaha problem

Yes I did change the fuel filter, plugs, thermostats, poppit valve,& even water pump after the decarb. I will search on how to test the horn. I havent done anything with the fuel pumps yet, but when I first got the boat about 2 years ago I did the carbs. I will test the horn & post back. Thanks for being so helpful.

 

[bigbrownbuku]

Re: 1990 200 Yamaha problem

an easy test for the horn is ground out the high temp switch wires running to the cylinder head. a small black rubber piece holding a shiny metal disc in place with 2 wires coming from it.

 

[i_build]

Re: 1990 200 Yamaha problem

OK, another issue not mentioned is that my choke & digital guages have also been working intermittently. I also noticed that the buzz that I normally hear from the oil tank area at start up is non-existent. Hence Ray's bad ground theory comming to fruition. Cleaning & Tightening the ground connection made the guages come on, and the choke work & oil pump began buzz... But the ground cable going to the engine was far beyond repair. Cut 3 inches off the ground cable to try to get to clean copper, but still hit corrosion. I'm going to replace the cable entirely tommorow. I will posts back results.

 

[i_build]

Re: 1990 200 Yamaha problem

HUGE DIFFERENCE in idle , performance, accesories... my nav lights that did not work now work. I guess I have to stick to the philosophy of checking the smaller things first. Thanks you guys... keep up the great work.