1973 85hp

[matt88]

Just bought a boat with a 73 model 85hp mercury and need some advice about whether I should rebuild the carbs or not. I have not had it on the water yet so I have no idea how it acts under a load. When on the hose in the driveway it will not start until I squirt gas in the #2 cyl. I dont have a spray bottle setup so this is the easiest way for me to get it running. After which it seems to idle ok and will start back easily after I shut it off. The bulb stays hard so I guess I can assume its getting fuel. I already ordered the kits for the carbs but I would rather not tear into it if I dont have too. Any advice is appreciated,thanks.

 

[SeaKaye12]

Re: 1973 85hp

Hi Matt,

It certainly sounds like your carbs need some attention. Does your engine not have a choke? I have a newer (1978) Merc 850 and I have an electric solenoid operated choke which can also be actuated manually at the engine.

You should be able to activate the choke and then advance the idle speed with the second lever on your MerControl. Mine always starts easily when I do that.

Keep in mind that your engine gets all its lubrication via the fuel. Many times if you have dirty jets in the carbs you end up running lean which can burn through your pistons.

So; in addition to quality of idle and hole shot...cleaning the carbs helps give you piece of mind.

You might not need to tend to it the first week; I can understand your desire to get out on the water and see how she runs. But; get to the carbs before you put a lot of WOT hours on her.

BTW...two other "must do's"......Change the lower unit oil and check or replace the impeller.

Have fun,

Chuck

 

[matt88]

Re: 1973 85hp

I ordered an impeller as well. I guess I will probably rebuild the carbs before I take it out. Been on the water more than once with a dead boat. Not fun. Should the motor shut off when I unhook the battery? I know on a car it would indicate the charging system is bad. Whats the voltage that should be on the cables when running?

 

[SeaKaye12]

Re: 1973 85hp

Not a good idea to unhook the battery when your engine is running. On a lot of outboards; you do that; even for a moment...and you can fry electrical parts. Like your rectifier.

Boat ignition systems are a lot different than cars. I made the mistake early on by assuming that my knowledge of car mechanics would keep me from screwing up on the boat. Not so.

On my boat; I get 16v or even more when the engine is running and charging. It depends on the state of charge of the battery and the load that you have on it (lights, etc...).

Your engine has no voltage regulator; so the voltage can climb rather high and it's up to the battery to absorb it. Hard on batteries and very hard on electronics. If you have a stereo or fishfinder or the like; guys either have a second battery for that; or install voltage regulation.

Chuck

 

[dwco5051]

Re: 1973 85hp

Got to agree with Seagaye12 that in can be bad for the electronics to disconnect the battery while the engine is running. Yes the motor will run without a battery as the ignition system is independent of the battery. You could rope start the engine without any battery and it would run. The key switch grounds out the ignition to stop the engine. Keep this in mind as there are situations when working on outboards that they could start with the wiring harness disconnected and the flywheel is turned by hand.

 

[matt88]

Re: 1973 85hp

Got the carbs off and in the dip cleaner. I have never seen any as gummed up as these. Fuel was completely blocked on the filter of the lower carb. Working on the water pump now. As for unhooking the battery. It does in fact shut off the engine when I disconnect it so would that mean the rectifier is bad? As for applying auto repair knowledge to outboards I guess we all have to learn somehow,right? I usually have to learn the hard way on everything. Helps me remember when I do it again,lol. Any advice on the best way to diagnose my electrical problem?

 

[SeaKaye12]

Re: 1973 85hp

Hi,

Not sure if it was mentioned earlier, but CDI has some directives on trouble-shooting.

http://www.cdielectronics.com/downloads/troubleshooting guide/

Some of it can be done with just a simple volt-ohm meter; other tests require a DVA adapter which enables a digital voltmeter to display the peak voltages produced by a component.

Good luck; this forum can't be beat.

Chuck