Does my Johnson put out right?

[kf4pfw]

150TL78S/J5008422

#1, is there any sort of history available on this motor? I know, it's 30 yrs old so no go

#2, I noticed that when I go fishing and return, my cranking battery is usually between 75% and 85% of capacity according to my Schumaker charger. The Volt Meter and my DMM both confirm that at WOT I am getting about 13.4-13.8 VDC on the cranking battery. Does this seem correct? Why do I have to recharge my cranking batter so much? Usually, when I fish during the day, the guages (fuel, tach, vm), two fishfinders (Cuda 168 and Pirhana 15) are turned on all day. At night, add in nav lights and guage lights.....

Does my Johnson put out right?

[Legend Chris]

SOunds like a personal problem....(Does my Johnson put out right?)

[JVC]

Do you feel satisfied afterwards? Only you can judge if it (or she?) is doin' OK for 'ya.

:)

[Neveredge]

That motor only has a 9 amp alternator. That is why your battery is going dead each trip. The motor doesn't make enough juice to recharge what you are using.

[kf4pfw]

Anyway to increase the output? I would have thought that it would have been 35amp at a minimum! 9 Amps huh?

Thx

[lkhartwl]

your motor is 10 amp, it should keep the motor charged. Champ had a old 150 the other day that was a 10 amp model and well he had no problem charging it was many other problems he had. you need to have a certified tech check the charging system also you need to if possible take off the livewell and such connections and add another battery just for them as if you are using them a lot the charging system may not be enough to cover their use.
Changing to a 35 amp can be done but only by a certified tech as you will need a new flywheel and such and a lot of electrical parts, which are hi dollar.
take it to a certified tech and have him check it out.

[kf4pfw]

Good suggestions! I've done a cursory glance through the troubleshooting steps and it looks like I *may* have a rectifier going bad.....I know that I can spend 8--10 hours on the water running the OB for maybe 20-30 mins of that time. Hooking my DMM directly to the batter shows 14 VDC at WOT which according to the SM is what I should expect.

Adding a 4th battery is a great idea except for the weight and the space, of which there is none for the additional battery. I think I'll keep things like they are and tackle the problem myself this winter while I am doing some other major projects on the engine.

Mike

[Neveredge]

The 9 amp units (some say 10) don't put out enough juice to run your electronics and run your motor. I had a 79 Johnson 150 that couldn't keep up with the depth finders and engine gauges. I always had to re-charge the crankin battery after every trip and I used that boat hard for 7 years.

It only makes 9 amps at WOT. At more modest rpms (where most of our running time is spent) it might only put out 2 amps or less. This is why the battery gets run down. If you have other electrical problems it will only make it worse. Get it checked out.

It is not worth the effort to switch to the 35 amp system although it isn't all that hard to do. The main reason I wouldn't do it is because the 35 amp system robs 7 hp from your motor (dyno proven, don't listen to the people who say it isn't true, call Al Stoker if you don't believe me) and your motor only makes about 135 at the prop anyway so you can't afford to lose 7 more.

I would switch out to a more modern 9 amp system though. And when your gearcase finally goes I would swap the intake for a 79 or newer and put a set of GT150 or smallbore 175 carbs on it. That would boost your power to about 165 without doing anything else. (re-jetting would be necessary) Hope all this helps a little.

[kf4pfw]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Neveredge &raquo;</TD></TR><TR><TD CLASS="quote">The 9 amp units (some say 10) don't put out enough juice to run your electronics and run your motor.

It only makes 9 amps at WOT. At more modest rpms (where most of our running time is spent) it might only put out 2 amps or less. This is why the battery gets run down.

It is not worth the effort to switch to the 35 amp system although it isn't all that hard to do. The main reason I wouldn't do it is because the 35 amp system robs 7 hp from your motor (dyno proven, don't listen to the people who say it isn't true, call Al Stoker if you don't believe me) and your motor only makes about 135 at the prop anyway so you can't afford to lose 7 more.

I would switch out to a more modern 9 amp system though. And when your gearcase finally goes I would swap the intake for a 79 or newer and put a set of GT150 or smallbore 175 carbs on it. That would boost your power to about 165 without doing anything else. (re-jetting would be necessary) Hope all this helps a little.</TD></TR></TABLE>

Thanks for the advice! Sounds like you might have done this before? I know I am probably being stupid as hell, however when the motor does go, I fully intend to rebuild unless I have a catastrophic failure. As seasoned as the block and turning components are, I think I have a really good engine. Compression is around 70-75 on each cylinder and I have slowly been working the problems out (anyone else that rides with me always comment on how well the engine runs), particulary the cold start problem I have had since day 1.

Thanks again