Hard Starting Mercury 9.8 Outboard

[Flying_gage]

I am new to 2 stroke outboards, so bear with me.



Just bought the above on a 14' Jon Boat. It is a 1977 model. I was told by previous owner that he replaced impeller 3 years ago and that is all the maintenance he had to do. No further history.



Had it out for about 1 1/2 hrs today and it started on 2nd pull and idled well. Ran it under various loads without issue.



When I got back to ramp and idled it down it died. It was then a pain to get started and only did start when I pulled out the choke.



The previous owner told me he winterized it and I have no reason to doubt him. Today I added 3 gals of fresh fuel to the tank with the proper mixture and a double dose of seafoam, (12 oz to 6 gals of fuel).



My concern is overheating? I will do the impeller here shortly yet it has a strong and steady stream out the discharge port. Could it be as simple as a fuel filter or carb needing rebuild?



Thanks in advance!

 

[Skydiver]

That is a fine engine.
With it cranking easy the first time sounds like it's got good fire. Check the sparking plugs. Fouled plugs cause difficult starting.
Did the previous owner run the carb completly dry before storing or add sta-bil? Did you use a NEW fuel line? If ethanol gas is used it will soften the rubber and clog jets.
Sounds like you have trash in the bowl. When you pull the bowl you might/will see some trash.
Tips: Never add extra oil to any two cycle. More 2-cycle oil means less gas and less gas is a leaner mixture. Not good
Might check the thermostat. They are small and grit can clog them . A rubber impeller will/can burn up in a few seconds when ran dry. I always coat a new impeller with some vaseline.

 

[Gary - K7GLD]

I had the Gamefisher version of that motor - well built, but hard to keep properly adjusted for low speed trolling - ended up buying a 9. 8 Nissan, which also makes the Mercury version. The advice for care in fuel/mix is right on - any tendency to over-oil "just to be safe", will get you a poorly running motor and fouled plugs. I wouldn't get paranoid over the pump impeller, AS LONG AS there is a steady and substantial pee-stream on output. I still have a spare coil, carburetor, and aluminum prop from mine - sold the engine right after buying the new Nissan...

 

[JPS]

I had a 20 hp Merc. Did about what you are talking about. Changed to synthetic 2 cycle oil, problem over. Might be worth a try!! jps

 

[Hoefler]

Rebuild the carburetor. On an engine that old, it is not designed to run on RFG ( Re-Formulated Gas ) that CARB required the nation to switch to in 1998. The new gas has a history of eating the gaskets, floats, and some of the plastic component out of the carburetor. Most common, the high speed nozzle well gasket. I have seen many of these go unchecked until the motor quits entirely. Then it is to late. What happens is when the gaskets fail, you wind up with a lean fuel condition, your lubrication is in the fuel. Lean out the fuel, lean out the oil and you get a scored pistons. I have seen it all to often in my boat shop.

 

[Flying_gage]

Thanks guys. I cannot attest to the fuel that was in there when I purchased it, but I did purchase a measuring device and my mixture was spot on.

Makes sense on the rebuilding the carb though. Any suggestions on where to get a kit?

Gary - K7GLD you wanna sell your parts?

 

[Gary - K7GLD]

Makes sense on the rebuilding the carb though. Any suggestions on where to get a kit?



Gary - K7GLD you wanna sell your parts?

I got all my spare stuff on Ebay, not hard to find stuff, just might take a little while - seems to be a fair amount of replacement parts floating around. Re-reading your lead post, looks like your particular motor is a '77? Mine was a '94, and while all the comments offered here certainly apply to your motor, the '94 parts I have might not fit your older model - and by the way, IF you can find non-Ethanol premium in your area as we can here, it will almost CERTAINLY run better in your motor than the Ethanol regular junk - at least it did/does in mine - and is well worth the slight added cost!

 

[Hoefler]

Thanks guys. I cannot attest to the fuel that was in there when I purchased it, but I did purchase a measuring device and my mixture was spot on.



Makes sense on the rebuilding the carb though. Any suggestions on where to get a kit?



Gary - K7GLD you wanna sell your parts?

Go ahead and buy the OEM kit from Mercury, the pennies you might save are not worth it in the long run! Been there, done that, won't do it again!!

 

[Wygate]

The new fuel is killing the boating fleet in all gas eng's big and small. keep a spare prime bulb and hose with correct fittings (o-rings go bad) for your tank/ eng with you. If you have a good discharge cooling should be fine. As for parts you get what you pay for, got oars?

Also water (condensation) is a big deal with small eng's, wont kill it but wont run quite right if it gets stuck in the fuel sys and may not show up like you might think. Water dose not flow or atomize the same as gas, gets stuck in some places and limits fuel flow.

good luck

 

[Skydiver]

Wygate, you are correct. Marine mechanics are being over whelmed with clogged carbs due to ethanol gas. A product called "Power Tune" has saved many hours labor. You must spray it into the fuel port and let it sit overnight. Power tune is made by quicksilver and sold by most marine dealers. It really works. It is 10 times stronger than regular carb cleaner. It will clean jets, but will not remove pieces of decayed fuel line.