Help: Mercruiser Trim Pump Blows Fuses

[Slip Away]

I replaced two blown fuses, both 20 amp on the port trim pump last week. The trim and tilt worked fine at the slip. Once we got out on the water and anchored, neither pump would work. It blew the fuses while I was trimming the drives up apparently while on plane.

Not to knowledgable about this. Any help would be appreciated as to what to check or look for. I can buy a case of fuses and replace them, but that is just a band aid, need to figure out why it is blowing fuses.

Have twin Mercruiser 4.3L V6 with Bravo III drives. Fluids in both pumps are full. New batteries in the boat this season and they are fully charged.

 

[slredstorm62]

Re: Help: Mercruiser Trim Pump Blows Fuses

i would check your wires. you might have a loose wire that was fine until you started going and it wiggled itself to a ground and keeps shorting out.

 

[Slip Away]

Re: Help: Mercruiser Trim Pump Blows Fuses

There are dozens of wires to check, I looked at quite a few when I replaced the fuses, and all looked fine. I will look at the rest if I can find all of them and where they go.

 

[Bt Doctur]

Re: Help: Mercruiser Trim Pump Blows Fuses

Dont know what your looking at but there is only 1 fuse for the control button and thats right at the trim pump. http://www.boatfix.com/merc/Techbk/97/97hs6.pdf

 

[Slip Away]

Re: Help: Mercruiser Trim Pump Blows Fuses

I already have that info, and it is not what is on my boat. There is an inline 20 amp fuse in a fuse holder for each pump, connected direct to the batteries. That is blown.
There is a 20 amp Bussmann fuse at the trim pump itself, that is also blown.

Finally there is a 110amp fuse connecting to the starters on each motor, neither of those is blown.

So the question remains, what is causing those two 20 amp fuses to blow when under load only ?

 

[tanker7203]

Re: Help: Mercruiser Trim Pump Blows Fuses

Check your trim limit switches and wires look outside and in. I had the same problem. They crumbled in my hand. When ther was no water worked fine in water shorted out.

 

[Slip Away]

Re: Help: Mercruiser Trim Pump Blows Fuses

Boat is always in the water. Once fuses are replaced they work fine in the water and in the slip. Once underway, and try to trim, fuses blow.

Oh well, I guess I will live with it for the balance of the season. And in the off season have someone who knows what to look for check it out.

Thanks

 

[Bt Doctur]

Re: Help: Mercruiser Trim Pump Blows Fuses

On a merc system there ARE NO FUSES ON THE MOTOR LEADS
5 or 10 amp on the small red wire to the control buttons.
110main thru the square block to the solenoid buss

 

[Slip Away]

Re: Help: Mercruiser Trim Pump Blows Fuses

On a merc system there ARE NO FUSES ON THE MOTOR LEADS
5 or 10 amp on the small red wire to the control buttons.
110main thru the square block to the solenoid buss

On SOMEmerc systems, what you say is true. However on the merc system on our boat, there are two 20 amp fuses per pump, and one 110 amp fuse per pump. Believe me I know, I have replaced all of them except the 110 amp fuses.

Thanks anyway for your help.