problem with my 98 johnson 90 hp outboard

[bizle]

first off im new to the site so i guess this is a good time to say hi!

i bought a 1998 pontoon boat a few weeks ago and everything has been great untill yesterday
we got to the river a had a dead battery so we used a friends jump box
but it was almost dead and wouldnt start the boat

anyhow after hooking up the jump box it blew a 30 amp fuse back by the battery so i replaced the fuse and put a good battery in the boat and it started right up
the problem is something went goofy with my tach the needle points stright down and when you start the boat the tach is going backward
i took the face off the tach and tried moving the needle but its still the same?

i have been searching the net and read up on rectifiers but im not sure if thats the problem or if somehow the tach got messed up?

i started the boat and unhooked the battery cables and it kept running so does that mean the charging system is ok?

its a 1998 johnson 90hp spl 4 cyl 2 stroke any help would be great
also the tach is a faria system check tach if that matters

 

[jonesg]

Re: problem with my 98 johnson 90 hp outboard

oh man, you seriously need to read a manual before wrenching around engines, boy oh boy. Get the service manual, factory only.
www.outboardbooks.com

From Mastertech Bill Kelly,
"The other QuickStart models will run the engine without the power coil being connected (of course this will burn out the control circuits inside the power pack)."

You may have damaged the powerpack already.

The way to test charging is just put a meter across the battery terminals and compare voltages between stopped and running.

I'm wondering if you hooked the battery up in reverse, that usually blows the rectifier.

Its usually a good sign to pack up if the battery is dead and it blows fuses, these engines don't take to jury rigging, better to sort things out than force the issue.(dismantling the tach is forcing the issue)

At this point I'd start with a fresh battery and a voltmeter and see if its getting a charge when running, if not then the rectifier/regulator might be shot.

 

[bizle]

Re: problem with my 98 johnson 90 hp outboard

jump box was not hooked up backward

also i went and got 2 new marine batterys and a selctor switch so now i can switch from one battery to the other or turn everything off when the boat is just sitting

everything seems to be fine other than the tach the needle is pointing stright down and when you rev up the motor the tach is running backward
everything else works great

if the boat is running and you disconnect the battery cables should the boat stall?

 

[wilde1j]

Re: problem with my 98 johnson 90 hp outboard

If you disconnect battery leads from a running motor, you just bought, at minimum, a new rectifier. The motor will probably continue to run, since ignition is magneto, although, since your motor has a power pack, it will stop.