Boat mechanics?...40 hp mercury

[Nastytater]

I've got a problem with our 2000 model 40 hp mercury. But instead of trying to explain everything it's doing,I'm going to give full detail on what I know about it.
When we got the boat,we was trying to raise the motor up for towing using the tilt trim and a set of jumper cables. We raised the motor and the guy took off the cables laying the hot cable directly on the aluminum door to the battery compartment,causeing smoke to come out from under the motor where the motor bolts to the mount. Thats the first problem. Second problem,when we was finally able to get the boat on the water,we noticed that it wouldn't plain,nor would it even get over 1600 rpm's. You could put it in high gear and it would just shut off. Idles perfectly for as long as you want it too idle,but wouldn't kick into high gear. Thinking that maybe the high speed jets were clogged,Dad used some stuff called 44k fuel system cleaner made by BG products. Dad replaced the fuel with 12 gallons fresh gas. And he also put a 1 pint bottle of the outboard oil directly into the tank with the fresh fuel. (Basically as an extra precaution to the self oiler.)
We tested the boat again and still the boat wouldn't get over 1600 RPM's. On the way back to the dock,dad tried choking the motor as we was moving across the lake. The rpm's jumped up like it wanted to take off,but soon idled back down. Pushed the throttled down some and gave it another try with the choke. It jumped again up to 2500 Rpms. We kept doing this in hopes that it would clean out the high speed jets,but eventually,a buzzer(more like a whistle) went off. We immidiately shut the motor down. Curious as too whether the motor froze up,we started the motor up again and it started,but we shut it right back off considering the buzzer was still alarming.
Now,since we have got the boat back home,and trying to figure out what is wrong with it,we have found a fuse on the back of the engine on top above the cylinders that will shut the alarm off if you pull out the fuse. BUT,when you plug it back in,the alarm still sounds. AND,ever since we unplugged the fuse,the motor won't even hit a lick. Don't ask me why Dad is still trying to start the motor with the alarm sounding,cause I have no idea. I guess it's cause he added another pint of oil to the tank and was hoping it would smooth it out. Anyways,I'll stop explaining things and hope someone can try to make sense of this. Thanks folks. All statements are appreciated.

 

[NE GA Pappy]

Clean the carbs. The high speed jets are plugged. Disassemble them and clean them well.

I would say the alarm is for overtemp. When was the water pump last replaced?

 

[Nastytater]

Honestly,I'm not sure. The motor was peeing perfectly so I'm supposeing that the water pump was working properly. The boat sat for 3 years before we bought it this year. The guy that sold it too my dad was a good friend of my dads and he said he'd been starting it up on a regular basis,but he also doesn't take very good care of a boat. We found that out cause he didn't even bother to put a cover over the boat and it was parked outside.

 

[Lukikus2]

Clean the carbs. The high speed jets are plugged. Disassemble them and clean them well.

I would say the alarm is for overtemp. When was the water pump last replaced?

X 2 on the jets. No cleaner will unplug them if they are stopped up.

Make sure the vent on the fuel tank is open and getting air in. Sometimes the 'O' rings in the vent can go bad and not let enough air in. One way to check is when trying to throttle up, hold the primer bulb and see if it's trying to suck itself inward.

The fuse should be to the power pack. If it's still good no harm was done with the jumper cables.

The alarm is either for high temp or no oil. Is that motor oil injected?

 

[Bilge Rat LT 20]

Motors that sit up for years even with the occasional startup need a few things done.

Replace waterpump, it's rubber and gets brittle. T stats and poppet valve if equipped needs replacing.
While these are being done clean out any passages. Crud,bugs and corrosion get into the water passages. Use heavy weedeater line to poke into water tubes from waterpump to head and into peehole.

Rebuild carbs and replace primer bulb and fuel hoses. Clean fuel tank and clean all electrical connections,plugs and battery cables.

Oil and grease everything, put some on prop and driveshaft during WP replacement.
Do all this and then you can start looking at other problems. If you don't these things will become problems quick and any cooling and fuel problems can cost you a powerhead.

 

[Bilge Rat LT 20]

Also clean the oil tank,filter and replace old oil with new . Oil collects water over time and gets thick long before it looks like it has water in it. Thick oil will not meter like good oil and powerhead can go boom.

Replace any and all filters.