I'm gonna blow a Fuse!!!

andreworiordan · 27 April 2011, 18:39

Hi all, I have a 90hp 4 stroke Mercury engine, the year is 2004. over the last two weeks It has been blowing the 20amp fuse in my engine, I would be driving away and and it will blow, I have checked the cables in the engine looking for a short circuit but cant find anything obvious, it sometimes blows when i'm tilting the engine and today I noticed that it just blew, didn't even touch the tilt which makes me think its not a problem with the tilt switch, it goes at random time, She might run all day then blow when i'm tilting the engine up, then the next day it might blow 3 fuses and then be fine, any ideas?

When it does blow I loose my trim, my Rev gauge freezes and if i try start the engine it obviously has no power so it does nothing

Any help would be great, I was hoping to be up and running doing tours this weekend but this is making me very nervous bringing paying passengers out on my boat.

Thanks Guys

andreworiordan · 27 April 2011, 18:45

The Engine in Question

Jeff · 27 April 2011, 19:03

Worth checking the wiring from the throttle box up into the handle - often chafe around the pivot

Chris · 27 April 2011, 19:11

its going to be chafed wires somewhere, water in something start at the control box and work you way back.

you can disconnect things and run it for a while to see it the problem stops. e.g. the trim. Try disconnecting at the control box and run without it for a while. Then try disconecting at the engine harness.

andreworiordan · 27 April 2011, 19:12

will have a look at that tomorrow, whats strange is how random it blows, i'm gonna make a full list of what might be causing a short circuit and go through everything i can, i was thinking of disconnecting the wiring loom and tilt up/down and see if it blows, if it does i can rule out the controls, next maybe disconnect the tilt switch on the engine, I was talking to a few people and they mentioned maybe a damaged magneto?

Boats&Outboards · 27 April 2011, 19:20

Quote:

Originally Posted by andreworiordan

will have a look at that tomorrow, whats strange is how random it blows, i'm gonna make a full list of what might be causing a short circuit and go through everything i can, i was thinking of disconnecting the wiring loom and tilt up/down and see if it blows, if it does i can rule out the controls, next maybe disconnect the tilt switch on the engine, I was talking to a few people and they mentioned maybe a damaged magneto?

They wernt engineers by any chance.....pardon my scepticism

Start with the wiring, it's got to be something silly to be so random

Peter ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

andreworiordan · 27 April 2011, 19:47

is it happens I was talking to a marine engineer, he is a pure legend of a man!

So i guess its a case of looking at every bit of wiring on the engine, could it be anything to do with the motor in the tilt unit itself, There is a bit of rust on the motor case itself and makes a louder noise when tilting the engine down.

also will need to have a look at switches to see if there is any water getting in there

Justribing · 27 April 2011, 20:18

It may be worth getting someone to megger the motor for you if it has water in or a short it could cause this.

Is there anything thats tight, in other words is something drawing to much current or is something maybe shorting. Same result blown fuse different causes.

Razorbill RIBs · 28 April 2011, 07:52

Quote:

Originally Posted by Jeff

Worth checking the wiring from the throttle box up into the handle - often chafe around the pivot

As others have said, could be lots of places, but I have had this when we had a dodgy ignition barrel......intermittent problems

Good luck tracking it down.....

biffer · 28 April 2011, 07:58

start it up and wiggle as many wires as you can lay your hands on, might throw up a fault

Boats&Outboards · 28 April 2011, 10:16

If it was the PTT motor all you'd get is clicking on the solenoids when you trim up/down, normally when the motor fails it fails, end of...and even then it's the brushes which need changing. It's normal to have corrosion on the housing. Saltwater.

Give it a light hammer test and that will show if it's beyond service. You can replace the casing if needed but not really worth it better to get new PTT motor Instead.

Like others have suggested you can eliminate the PTT system but disconnecting it from use.

My bet is bad earth somewhere. Finding it is a whole different story. Be careful what wires you wiggle when running though :-)

Not sure if your motor has the diagnostic plug in. May help pick up faults to get I plugged in and checked.

Peter

Peter ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

two stroke mick · 28 April 2011, 13:44

Andrew

Class looking rib. do the tubes touch on the water when at rest. I.e. is it suitable for diving

Leslie

andreworiordan · 28 April 2011, 20:11

I don't believe my engine has a diagnostic plug in, I'm down tomorrow to hopefully find this problem , the plan so far is to disconnect the ptt switch on the control by unplugging the loom, then failing that i will unplug the switch on the engine controlling the ptt. failing that have a poke around looking for any loose connections or damaged cables, failing that I will undo the 4 bolts and leave her swim, maybe use it as a small mooring block?

andreworiordan · 28 April 2011, 20:21

TSM, She is a great boat, built by Excalibur www.ribs.ie if you have any questions give Joe a shout, Very happy with the boat no problems! soon it will be the same for the Engine...I hope

Waterman · 29 April 2011, 09:51

Just from looking at the pics, fairly new engine and has an ecu/ecm. I Would be very confident your outboard does have a diagnostic plug. Give Joe Mc a shout, as far as I know he has the mercury diagnostic kit.

Boats&Outboards · 29 April 2011, 10:48

Quote:

Originally Posted by andreworiordan

I don't believe my engine has a diagnostic plug in, I'm down tomorrow to hopefully find this problem , the plan so far is to disconnect the ptt switch on the control by unplugging the loom, then failing that i will unplug the switch on the engine controlling the ptt. failing that have a poke around looking for any loose connections or damaged cables, failing that I will undo the 4 bolts and leave her swim, maybe use it as a small mooring block?

That's a very expensive mooring block!

Any pics of under cowl or PTT motor

It's the 2004 onwards EFI which has plug ins, I think. Not sure though and my engineer is away at the moment to ask

Peter ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

Waterman · 29 April 2011, 14:52

Hmmm, my 2001 opti has diagnostics, so can't see why your new(er) four stroke wouldnt??

andreworiordan · 01 May 2011, 17:09

well, yesterday I went down and had a good old look, I tilted the engine using the tilt on the throttle lever, as it lowered I shook it a bit and bang, there she went. So I started there, stripped down the box and sure enough there it was two brakes in two cables, so repaired that and now all is running perfect, its nice having the PTT back.

Boats&Outboards · 01 May 2011, 17:43

:-)

Now you have a new problem. What you going to use as a mooring block now then!!

Peter ~ askboatsandoutboards4sale@sky.com ~ 07930 421007