Three questions

[sherwindu]

I have three questions concerning my Yamaha 9.9 four-stroke outboard.<br /><br />First concerns possible overcharging from the alternator and what to do about it.<br />The alternator has a max output of 10 amps. Even feeding a bank of two wet-cells<br />in parallel, that's a lot of current to feed in over an extended time. The batteries get<br />up to 14 volts and possibly higher. Will this high charge rate hurt the batteries, although<br />they will build up resistance as they charge up? Would there be any damage to the alternator if it<br />were disconnected from the batteries at any time?<br /><br />Second question concerns the susceptibility of this engine to develop blocked jets<br />in the carburetor. Although I have and inline filter from my tank and another filter<br />in the engine fuel line, I had to clean the jets today after doing the same job a month<br />ago. Although I did not use the engine hardly at all in the interim, I was made sure<br />to run it for a few minutes every week, but it got progressively worse. My gas is typical gasohol, which I bought the beginning of the season. About mid season I added a carburetor cleaner and gas preservative to the main gas tank. Both my filters do not look very dirty. Pulling the carbs and cleaning the jets is a half day job,<br />so this is getting a bit tedious. Maybe they will someday design a carburetor with a built-in cleaning mechanism, like a needle plunger which can be operated without pulling the<br />carbs.<br />Seems like these types of carburetor problems are almost an epidemic, as engines are lined up at my mechanic for this same problem. Four strokes are<br />especially susceptible to this problem because of their fine diameter jets. Any ideas on how to minimize this problem?<br /><br />Last question is about throttle handle behavior. When increasing throttle with the handle control,<br />my engine does not react immediately and then it<br />reaches a point where it increases quite a bit with just a small turn of the handle. I can then<br />back off to try and find a good speed. Should there not be a smooth increase of engine rpm as the handle is turned?

 

[rodbolt]

Re: Three questions

question 1 is no worries. keep a monthly check on the battery water level and do not use maint free batteries just like the service manual says.<br /> question 2. running a few minutes a week with 2 month old gasahol is a waste of time. run the motor under a load for at least 30 min each week and dump any gasahol over 60 days old. also use a stabilizer at each fill up.<br /> question 3 is a matter of how the engine makes power. if you want a motor with a purely linear power curve buy an electric. a gas motor must make RPM to make power. so as the RPM builds so does the powercurve. as the curve increases it allows the prop to spin up. has the WOT RPM been checked to insure the prop in the box was actually the one your hull needs?<br />pulling and cleaning the carbs on an F 9.9 is an hour and a half if I need coffee in the meantime. but your correct on the fine jetting. no room for errors. we also reccomend a ten micron filter.

 

[sherwindu]

Re: Three questions

If I understand you correctly, it's ok to pump 10 amps into these batteries on a continuous hourly period, as long as you don't boil all the acid out of them. I also assume there is no regulator on these engines. I would suspect the current flow slows down as the battery fills up with charge and produces more resistance to further charging.<br /><br />By the way, were you quoting carb removal time on a removed engine? Mine was in the water, and I had to carefully do this by leaning out over the transom. I may have exagerated slightly on the time. Do you also recommend any kind of cleaner<br />to add to the gas in addition to the stabilizer?<br /><br />I know there is some delay in the reaction of throttle to the propellor, which was sized by Yamaha in my High Thrust model. I was concerned about the narrow control of speed on the throttle handle which causes me to play with the setting to<br />get to the desired speed, going up and down until<br />it settles down to where I want it to be.

 

[rodbolt]

Re: Three questions

the speed thing is normal. what method was used to correctly size the prop. I am more concerned with that than aany of the rest<br /> I would have to go back and look up the specs to see if your motor has a regulated or non regulated system but its rated at WOT. below that the current falls off rapidly.