Mercruiser 4.3 blown ignition fuse

[kfrei]

2008 Searay 185 104 total engine time stored indoors original owner...ignition fuse (in forward fuse block) blown while cruising at 4400 rpm at end of a couple hours of tubing.. Engine just died...left instrument panel radio etc without power. Tried new fuses that blew immediately when key turned to run position (accessory position did not blow fuse). Thanks to this and other forums, I located a chaffed purple wire approx 2 inches below the alternator rubbing on the cylinder head. The chaffed area was very small and I think could be very easily overlooked even with good light. Also hard to believe on machine that is like brand new. It must also be noted that this short was intermittent for me during the investigation process as the wire in question is free to move around and is not forced against anything to short out. Thanks to others that pointed me in the right direction.

 

[Roy M]

Re: Mercruiser 4.3 blown ignition fuse

Today, I had a customer call with a similar complaint. The 15 amp fuse was blowing when the throttle safety switch was in the RUN position. We eventually found the culprit: the purple wire entering the coil was buried in a taped bundle that traversed the forward end of the manifold, then bent aft. Pulling up the bundle of wiring, we discovered that the electrical tape binding had been jammed deep into the crevice between the exhaust elbow (this being a Bayliner, 1998) and the valve cover. Pulling it up and VERY CAREFULLY unwrapping the tape, found that the insulation on the purple wire had barely worn, from engine vibration, and been occasionally grounding to the exhaust riser. We taped the worn wire, and the owner was able to get the boat home for more permanent repairs. We all felt good after this discovery.

 

[cr2k]

Re: Mercruiser 4.3 blown ignition fuse

Purple wires are keyswitch power. So that very well could be your problem.