1990 3.0 Litre: No power to gauges, switches, or engine. Trim works. Help!

[dieffer]

Relative newbie here.

Recently purchased a 1990 Larson All American 170 with a Mercruiser 3.0 Litre I/O (Model MCM 3.0 Litre W/DDIS.

When I got it, I couldn't get it to turn over. Noticed that 3 of the 4 spark plugs were unplugged (spark plugs were replaced this spring). Plugged those in. Dropped it in, boat would crank but not turn over, and then power to everything was gone. Figured it was the battery, so got a new battery. Hooked everything up, put it on muffs, got it running. Took it to a lake the next day, dropped in, turned over once but only stayed running for like 5 seconds, then died. No power to gauges, switches; nothing happens when key is turned. Trim works, but only down and trailer. No up.

Don't know if this is relevant, but boat worked all last summer. Spark plugs were replaced this spring. Trim reservoir, solenoid, and fuse were also replaced this spring. Says that system was tested and everything worked.

I'm stuck. Not sure where to look both in terms of why nothing is getting power now even with battery charged, and what could be draining it while it sits. Help!

 

[nola mike]

Relative newbie here.

Recently purchased a 1990 Larson All American 170 with a Mercruiser 3.0 Litre I/O (Model MCM 3.0 Litre W/DDIS.

Figured it was the battery, so got a new battery. Hooked everything up, put it on muffs, got it running. Took it to a lake the next day, dropped in, turned over once but only stayed running for like 5 seconds, then died. No power to gauges, switches; nothing happens when key is turned. Trim works, but only down and trailer. No up.

Trim issue might be separate, it's on a different circuit than the rest of the electrical.
You'll have to trace out where you lose the 12 volts. Easy first steps would be to check the 50 amp breaker in the engine compartment, and your ignition fuse. No gauges means that you're either not getting power to the helm (check the red wire coming from the engine) or your ignition switch is bad. If it cranks then you have power to your helm. If not, the problem is probably before that.

 

[dubs283]

Crank and turn over are the same thing. Crank/turn over and start/run are different things. Sounds like your problem is intermittent, check for as mentioned the 50 amp breaker, loose/corroded wiring, battery connections, make sure the 10 pin harness is plugged in all the way and held with a clamp, safety lanyard switch if equipped.

Trim issue sounds like the limit switch is misadjusted or has failed

 

[achris]

Time to break out the test light and do some diagnostics, not swapnostics.

Have a look up in the stickies, there is a post dedicated to 'it won't start', I think it's called 'Troubleshooting your starting system', or something like that..... Everything you need to know and do is in there.

Chris......

 

[Bt Doctur]

On a side note it appears you did not hear it run, water test it for operation only plunked down your money. Now you will be finding more issues that the previous owner did not want to fix.

 

[achris]

On a side note it appears you did not hear it run, water test it for operation only plunked down your money. Now you will be finding more issues that the previous owner did not want to fix.

Oh, good catch... I missed this...

...Recently purchased ...

Did you 'recently purchase' it without a test run?