multiple fuel/carb questions

[merc_650_72]

Hello, I just bought a 1972 Mercury 650. It was stored in a shed on a saw horse for the last 3 years. Right before it was stored it had a tune up. Not positive what that all included, but I know it got new spark plugs.<br /><br />The engine came with no fuel line what so ever. Temporarily, just to see how it ran, I connected my fuel line from my old tank directly to the fitting that comes out of the side of the engine.<br /><br />Question #1 - Do I need a fuel filter, and if so, what kind should I get.<br /><br />Question #2 - The engine starts great and idles pretty good (slightly rough). When I shift into forward and start to throttle up, it hesitates, and I have a feeling if I hammered it, it would die out. At higher RPM's it runs perfect and I can throttle a little down and hammer it no problem. The first time I started the engine, it idled way too high so I adjusted the carbs with the two screws in order to have a lower idle. Is that the correct way to do it? It seems to me those screws are for fuel/air raios not idle speed.<br /><br />Question #3 - Can you use a carb cleaner like STP for 2 cycle engines like this and would it help?<br /><br />Thank you very much! I hope I included enough information, if not just ask. I have a manual, but I don't know a whole lot about engines.

 

[LubeDude]

Re: multiple fuel/carb questions

Ok, Im not an outboard mechanic as some here are, but I know you probably messed up changing the Idle adjustment because it will idle slower in the water due to back preasure. (Im assuming you started it on muffs). Most will tell you to take the carbs apart and soak them in a carb cleaner of some sort, but I have had good luck with the spray carb cleaners myself, as you can inject the cleaner into the small holes in the carb and clean them out. So far I havnt found anything in a carb that this will not clean! Mybe Ive been lucky! You still have to take them apart! DO NOT spray them into the engine while running! There are no lubricants in them and they can cause engine failure!<br /><br />If it has been sitting 3 years you need to change your water pump impeller, your fuel pump diafram, and your lower unit oil also!

 

[chumbucket]

Re: multiple fuel/carb questions

Merc 650 If you get serial# then you can look up part's to see what all it may use. Did you have water to motor when you ran it? Should be some Merc 650 owner's jump in here to help you.

 

[JB]

Re: multiple fuel/carb questions

Howdy, Merc 650.<br /><br />First, replace the water pump impeller. They have a life span that is time based.<br /><br />Did you have the engine in the water and under load when you revved it up? How about when you fiddled with the carbs?<br /><br />Never:<br />Crank an outboard without water.<br />Rev a 2 stroke without a load on it.<br />Adjust carbs with no-load.<br /><br />Any of the above can end an engine's life.<br /><br />Yes, you need a water seperating filter.<br /><br />Spray carb cleaners intended for auto engines are useless on outboards.<br /><br />You probably need a Repair Manual. It is strongly recommended.<br /><br />Good luck.

 

[ZmOz]

Re: multiple fuel/carb questions

As I usually do, I would strongly suggest a dousing with Seafoam. Mix it with the gas and spray it through the carbs at idle. Don't use standard carb cleaner in a 2 cycle unless you take the carbs off. A water seperating filter is not necessary, although nice. My 1500 inline 6 didn't have a fuel filter of any sort for the last 30 years or so, it didn't die until I killed it due to lack of oil. I did add a $3 inline disposable filter, although it only filtered about 200 gallons out of many thousands in this outboard's lifetime.

 

[merc_650_72]

Re: multiple fuel/carb questions

Wow, thanks for the replies so far!<br /><br />So are the carb adjust screws supposed to be used for idle adjustment or is there something else for that? I adjusted them out of the water, so I'll have to do it again when I'm on the water.<br /><br />As for the water pump impeller it was replaced immediatly before being placed in storage. The lower unit was also rebuilt so there was no oil in it so I put new oil in already. There is a very good stream of water coming out the p-hole. Do you think I should still replace the impeller?<br /><br />Where would I be able to get some Sea Foam from? Should I mix it with the gas on a regular basis?<br /><br />I have a repair manual and I think I'm pretty good at following it (I replaced a lower unit seal and impeller on another engine before). So if you think I need to rebuild the carbs I probably could but I want to exhaust all other options first. <br /><br />Thanks again!

 

[ZmOz]

Re: multiple fuel/carb questions

Originally posted by merc_650_72:<br />So are the carb adjust screws supposed to be used for idle adjustment or is there something else for that? I adjusted them out of the water, so I'll have to do it again when I'm on the water.

Yeah, just adjust the screws, but it needs to be done in the water. <br /><br />

Originally posted by merc_650_72:<br />Where would I be able to get some Sea Foam from? Should I mix it with the gas on a regular basis?<br />

Napa is about the only place that sells it. There's a liquid version you put in the gas (seafoam) and an aerosol version you spray in the carbs. (deep creep) It's good to use in the gas about every 3rd tank or so, outboards are dirty little things...

 

[merc_650_72]

Re: multiple fuel/carb questions

Okay, I'll give some of that stuff a try and see what happens.<br /><br />Thank you all for replying!

 

[dilligafda]

Re: multiple fuel/carb questions

Originally posted by merc_650_72:<br />As for the water pump impeller it was replaced immediatly before being placed in storage. The lower unit was also rebuilt so there was no oil in it so I put new oil in already. There is a very good stream of water coming out the p-hole. Do you think I should still replace the impeller?<br />

If the engine has sat for more than 12 months without running, yes. As JB said "They have a life span that is time based." Especially when installed, they tend to take a "set" meaning that they take the shape of the waterpump housing and rarely return to provide good cooling.<br /><br />Good luck and keep us posted!