blowing ignition fuse when hot

[Stumpfinder]

I'm hoping someone can help troubleshoot. I've had my 1999 Bayliner Capri w/ IO Mercruiser 3.0 in the shop twice and they haven't fixed it. They've replaced the 30 apm fuse (under dash) and "tightened up the connections" but 90 seconds in the water I lose all power.

The fishfinder, trim buttons and horn still work, but gauges and engine are dead. Today, I waited for engine to cool down (while in the middle of the lake), put in a new fuse and got another 90 seconds of power - enough to get back to the dock. I noticed the temp gauge flucuating wildly so I unpluged the gauge but still blew fuse #4. Where do I start troubleshooting? Can I get a wiring diagram for this boat?

The wire to the 30 amp fuse is purple with red stripe (or maybe red with purple stripe).

This boat has only been serviced by professional mechanics, but now I have lost faith in them. $200 later I still have the problem. I have ohm meter and would like to try a few things before taking it to another shop.

Thank you in advance.

 

[Silvertip]

Re: blowing ignition fuse when hot

It seems odd that a 30 amp fuse under the console should kill the engine. Normally there is a circuit breaker or fuse back in the engine bay that protects engine electrics. Something is creating too much of a draw on that circuit so the solution is to identify that circuit and disconnect items fed by it, one at a time until you identify the offender. Just because a 30 amp fuse was removed, does not mean that fuse is the correct size. A service manual or wiring diagram for the engine is required to track this down. If you don't know how to read a wiring diagram find a buddy that does.

 

[flargin]

Re: blowing ignition fuse when hot

Service manual. Look Here: http://forums.iboats.com/showthread.php?t=251571

did you have any work done recently to the boat? add a fishfinder, stereo, etc?

30A fuse is pretty good size to be blowing. and the Red w/purple is the protected (fused) from battery. You said it was the fuse under the dash, not the circuit breaker on the motor correct?

What happens when you turn on the ignition, but do not start the boat, does it blow the fuse ?

 

[Stumpfinder]

Re: blowing ignition fuse when hot

Yes, it's blowing the fuse under the dash. Another boater who looked at the engine was puzzled that I didn't have a circuit breaker at the engine. But I will check again in the morning.

The fuse was blowing without turning over the motor - while it was still warm. I don't know if a warm engine has anything to do with it, but I will check again in the morning.

I had a fish finder added last year and have run the boat for many hours since then. Again, the work was done at the boat yard.

I can read a wiring diagram - I have worked on cars - but I'm not sure which manual to get: big vs. small block. Perhaps my former mechanic will at least tell me that.

Thanks again for taking an interest in my problem. You guys are the best. This is my first boat, obviously.

 

[flargin]

Re: blowing ignition fuse when hot

Try just turning the key to the first position, which would be where it normally would run... do not go to start the motor. just let it sit and see if it shorts, let it sit longer than your 90 seconds.

Welcome to iboats, some of the best guys around.

 

[Silvertip]

Re: blowing ignition fuse when hot

You have neither a big block or small block. You have a 3.0 four cylinder. Did you perhaps install the battery cables backwards? I can't believe this happens as often as it does since the terminals are clearly marked POS and NEG. Anyway -- it does happen and when it does it does damage.

 

[Stumpfinder]

Re: blowing ignition fuse when hot

Was able to test this AM. Turned switch on (without starting motor) and did not blow fuse. Gauges stayed on. What does that mean re: troubleshooting?

I found a wiring diagram and it says a 15a fuse should be where I have a 30a fuse. What's up with that?

I also noticed my tach "flutters" with engine off between 0 and 500 rpm.

 

[bruceb58]

Re: blowing ignition fuse when hot

Was able to test this AM. Turned switch on (without starting motor) and did not blow fuse. Gauges stayed on. What does that mean re: troubleshooting?

I found a wiring diagram and it says a 15a fuse should be where I have a 30a fuse. What's up with that?

I also noticed my tach "flutters" with engine off between 0 and 500 rpm.

I would disconnect all wires from the alternator and start with that first. Make sure you disconnect all the wires, just not the load.

 

[Stumpfinder]

Re: blowing ignition fuse when hot

Thanks, Bruce. Will do. If I still blow fuse, which components should I test next, and in what order?

Dumb question from newbie: should I only run the engine while in the water or can I do this test while on the trailer in my front yard? Not sure how fast it overheats w/o water. I could clean out a trashcan and fill with water if I have to.....

 

[bruceb58]

Re: blowing ignition fuse when hot

You can run it on muffs.

 

[flargin]

Re: blowing ignition fuse when hot

Thanks, Bruce. Will do. If I still blow fuse, which components should I test next, and in what order?

Dumb question from newbie: should I only run the engine while in the water or can I do this test while on the trailer in my front yard? Not sure how fast it overheats w/o water. I could clean out a trashcan and fill with water if I have to.....

I am assuming W/O implies without while out of lake. If you are implying how fast will it overheat with out any water. Pretty much immediately, and you will fry a number of critical parts.

Muffs will work fine, don't take it much past idle, since your house hose cannot supply enough water to cool a WOT motor.

 

[Stumpfinder]

Re: blowing ignition fuse when hot

AH! this may be a clue. After putting the boat in the water, my daughter started engine without lowering the drive. Ran for about 40 seconds before I could run down the dock and lower engine. Saw smoke. Which parts might fry and how can I check them? Never heard alarm. Temp gauge didn't rise.

You guys are kind. I feel like an idiot.

 

[bruceb58]

Re: blowing ignition fuse when hot

Smoke from where? Starting the engine with the drive up is hard on your u-joints but shouldn't cause smoke unless the water pickup on the drive is actually out of the water. Make sure you check your engine temp to see if your water pump is pumping still.

Has your engine overheated before? If it has, check all the wires that run near the exhaust pipe to make sure none of the insulation has melted off of them. That could be a potential cause of your fuse problem as well.

One more thing about the alternator. Make sure you disconnect the battery while you are in the process of taking off wires. Make sure you tape them and mark on them where they come off so you can put them back on in the proper place when you are done.

 

[Stumpfinder]

Re: blowing ignition fuse when hot

Thanks again, Bruce. I will have to trailer my boat down to the lake for this troubleshooting. Any other ideas I can do while I'm there would be appreciated.

I didn't think much of the smoke at the time because it was the first crank after winterizing. The temp gauge went up to around 170, but then started "fluttering" between that and 0. That's when I thought it might be a gauge issue and unplugged it.