OMC 115 Jet drive Fuse problem

[woodlark]

1994 Jetcraft Yukon River Boat. I bought this boat a little over a year ago from the Jetcraft Dealer in Anchorage Alaska, and have had problems from the get go. the current problem I am battling is the Tach will go crazy at high speeds and the fuse that lives between the key? and the starter selanoid will blow. This problem has been intermittent ever since I bought it. I took it back to the dealer during the initial warranty period but they could not get the darn thing to blow (typical), but found a crack in the hull...go figure. They fixed the crack but the Tach problem is driving me crazy I have checked all the connections dozens of times and cannot find anything loose that could be causing a short. I have niticed when the fuse blows, the tach will start to get erratic first jumping up and down then goes dead. The boat seems to loose power when this happens but does not always die. I cannot restart the boat untill I replace the itty bitty fuse that has blown. I have read the other post that are similar but they are missing the fuse part of the equation. If anyone has any ideas on what could cause such a problem, I would deeply appreciate it.<br />Thanks. James.

 

[clanton]

Re: OMC 115 Jet drive Fuse problem

I would check the purple wire that powers the tach for short to the black ground wire that grounds the tach. Follow the wire to and thru the control. Then check the wire from fuse to switch. The fuse only protects the wire from fuse to switch, the what every is connected to switch, starter solenoid, primer, tach, alarm sysem, gauges and acc. A color wiring digram would be helpful.

 

[DHPMARINE]

Re: OMC 115 Jet drive Fuse problem

James F I can only tell you I would start at the battery.Clean the terminals and tighten the wing nuts WITH PLIERS.(worse things ever put on a marine battery).Then check the other end of the cables,especially the ground lead to the block.And it's stud to block connection.<br /> DHP

 

[seahorse5]

Re: OMC 115 Jet drive Fuse problem

Most likely there is a regulator problem on the motor since it also generates the tach signal. It is located on the top aft of the block. An overheat, loose battery cables, or reversed polartiy can damage the regulator.<br /><br />It also uses a purple wire from the key switch in the regulator, and that could short internally and blow the 20 amp fuse. You have to check the charging system for full output and chances are its not putting out all the amperage.<br /><br />Check also under the dash for loose connections or chafing wires.

 

[Xcusme]

Re: OMC 115 Jet drive Fuse problem

James,<br />Take a look at a blown fuse. Is the fuse element melted in two or is the fuse blackened?? A melted fuse means that there has been an over current condition. This extra current was more than the fuses rating and the element got hot and melted. Common reasons for a 'melted fuse' are too many devices connected to the power line. The total current of all of the devices drew more current than the fuse was rated for, and the element melted.<br /><br />If the fuse looks blackened (where the element was), this denotes a dead short (some power lead had 'shorted' to ground). The sudden inrush of current during a dead short will vaporize the fuse element, that's the black part you see. Dead shorts are most commonly caused by bare wires contacting a ground surface.<br /><br />BTW, if you have 'bad connections', this will usually not blow fuses. Poor connections are usually points of high resistance. This high resistance limits the amount of current that flows thru the wires. You can temporarily replace the fuse with a lamp bulb for visual testing.

 

[rodbolt]

Re: OMC 115 Jet drive Fuse problem

hello<br /> I tend to agree with seahorse. from what you described it sounds like a regulator problem. jonnyrude electronics arent noted for there long trouble free lives. ther clue about the erratic tach would have me looking towards the charging system.

 

[woodlark]

Re: OMC 115 Jet drive Fuse problem

Thank you all, for your responses. I have checked the ground connections and battery terminals for mechanical connections, and all looks good. I will do some more testing with the purple wire. I have read other posts that talked about rectifier/regulator problems associated with the loss of power ) and Tach going funny (this only seems to happen when giving the boat throttle. I am thinking this may be the problem, could the rectifier cause that fuse to blow? I will need to do more testing. Does anyone know how to test the rectifier without running the boat? Is there an Ohm test one can do that will reveal if one of the diodes has gone bad? Does anyone know exacly where to hook the Garden hose up to this motor so I can run it in the desert for testing? I have an OMC manual for the boat but it does not show you how to hook up the OMC water connector I bought.<br />Thanks again.