Foul Spark plugs

[macojoe]

I have a 1989 Yamaha 175 model 175ETXG <br />The oil injection mercury switch went and it kept over flowing the the oil tank. Well I disabled the injection system. Now I have been mixing 50 to 1 and being very careful to get a good mix!! But ever since I have been mixing I am only getting about 4 to 6 trips out of it and the it starts breaking down till I can't get more the 3000 to 3500 out of it. I then change the plugs and it fine I get my full 5000? Now it is not very offten that I go WOT and I no that the injection system mixs 200 to 50 to 1 depending on the need of the motor.<br /> So should I mix less?? or could there be something else wrong?? <br />Thanks Guys

 

[roco]

Re: Foul Spark plugs

I've have a similar problem with an old Merc 20. I'm in the middle of trying to fix it. You could try a hotter plug--check with a shop--and/or you could change the thermostat. I understand that the water coming out the engine should be warm not cold and if it is not that will contribute to fouling of plugs. Worst case is that the rings are bad, and you're stuck with the cycle you described. My humble opinion of course. Good luck.

 

[macojoe]

Re: Foul Spark plugs

Well I do not think its the rings, I have compressinon test done that reades 123,123,122, down the lt side and 123 124 123 on the rt side.<br /><br />The water does come out warm. <br /><br />I use the NGK BR8HS 10 I belive. I did try he Champion version this last time but I have only been out once and it worked great, But as I said they go bad about the 4th time out. <br /><br />Someone else I no said to check the carbs one might be working badly, But then I should be lean, I think??<br /><br />Thanks for responce! Good luck

 

[jim dozier]

Re: Foul Spark plugs

Just a thought, are you positive you completely disabled the oil injection system?<br /><br />A poster on another post (Capt Ken) mentioned that he felt Yamaha ignitions/spark were not always as strong as other brands, if that is true your ignition system may be on the edge and the extra carbon may be putting it over.<br /><br />While I was testing my Suzuki oil injection I was using 50:1 premix combined with the oil injection and never had any carbon problems.

 

[macojoe]

Re: Foul Spark plugs

Well I belive so?? I disconected the pump and the alarm. There is no other oil in the boat at all, Only what I put into the gas tank my self. I have removed the remote tank, and I drained the tank on the engin so I am not getting any oil there.<br />I am still thinking that I am to rich, because I am at 50 to 1 and I almost never go WOT?? <br />I am so confused <br />But thanks for the replies!!

 

[jim dozier]

Re: Foul Spark plugs

Perhaps there is nothing wrong with your engine. I don't know the history on your boat, but in general it is better to be able to give the 2-stroke engines full throttle about 1/2 the time. They do not like to be lugged (strained at less than full throttle) for extended periods of time for just the reasons you are complaining of. Perhaps you are over propped and a smaller diameter or reduced pitch prop is in order. You've got that puppy in a corset and it can't breath. Unleash the hound.<br /><br />Another thought, are all the plugs getting visibly carboned up or just 1 or 2. Carb floats that stick open may make the associated cylinder run rich particularly at slower speeds. At higher speeds the engine demand can overcome the float leak. Also, a leaking inner fuel pump diaphragm can inject fuel into the associated cylinder causint the cylinder to which it is attached to run rich, but that would only be one cylinder.<br /><br />Also, I am assuming that you have checked with the manual and the plug heat range you are using is the proper one.

 

[macojoe]

Re: Foul Spark plugs

I am using what the book says as far as plugs go. As for the pitch of the prop goes I am using a 17 pitch which I think is to small?? I would like more out of the whole and less on the top end as I do nopt use the top end all that much.<br />All plugs are even in color and smell.<br /><br />So maybe I have to open her up more?? It is a 175 on a 20 foot wellcraft V20. I can do about 40 WOT but the boat design does not allow this unless it is a flat day, and how many of them do we get here on Cape Cod? <br />This time I changed from NGK to Champion for the plugs. I have only been out 1 time so lets see what happens. Maybe NGK is just junk, I hate them in autos! I like Auto light But they did have them<br />I will keep you posted, and again Thanks. Anyone else that might shade some light on this problem please do so.

 

[jim dozier]

Re: Foul Spark plugs

There is nothing wrong with NGK plugs. You might go one heat range hotter. If you can rarely get to WOT you may want to explore getting a prop that will allow a higher rpm at your current common speed. Think of it like this. Your boat in water is under a constant load of friction from the water, kind of like a car pulling a big load or going uphill. If due to the nature of the road you can't go very fast you would keep the car in a lower gear to avoid lugging the engine in 5th gear. A different prop would be like selecting a lower gear. Your hole shot would improve also. The only disadvantage would be that when you did use WOT you would have to avoid overreving the engine. It doesn't sound like that would be a big problem with you.

 

[macojoe]

Re: Foul Spark plugs

Thanks jamid for sticking with me! I got this prop because that is what I was told to get, But I have never been that happy with it. I have a old 15 pitch in the yard which is what this boat had on it when it was a I/O. And I think it had better performance. <br />The new out board set up out performs the old I/O every day of the week. But that 17 pitch don't seem to cut it. I am going to try that maybe tomorrow and I will get back to you on its performance, but I might have to do a few trips for the plugs to foul.<br />Again Thanks!!