Mercury 9.8 question

[robsd]

Hi folks, new here.<br /><br />My neighbor just gave me a 16' aluminum boat, trailer and a Mercury 9.8 motor. It's been sitting there for a while and he gave it up when I asked if he wanted to sell it.<br /><br />The question is on the motor. I stuck some mixed fuel in the tank and pulled a few times and it fired right up (probably sitting for years). It spit and sputtered so I replaced the 2 plugs (one was an Champion L78 and the other was an L78V...flat tip????). I pull it now and it'll fire right up but only run for a about 10 seconds. Runs pretty smooth. If I flip the choke back on (when it's about to die) it'll sometimes keep running. I tried pumping the bulb and it still dies. It will start right back up after it dies.<br /><br />The fuel pump seems to pump "some" fuel. I disconnected the line and started the motor. Not as much as pumping the fuel bulb but a decent trickle. I'm thinking about rebuilding the carb. I had to replace the fuel lines under the cowl. I also removed the cover on top of the carb and found a fuel filter (screen). It was clean. Any other ideas? It just sounds like it's running out of fuel.<br /><br />Another question, I searched the database and found people mentioned replacing the "impeller". Is this the water pump impeller for engine cooling? Seems I had to put the powerhead pretty deep in water to get water to pump out of the rubber hose on the left side of the engine. Is the pickup about mid way up? Once the engine was running a good flow of water was shooting out...and it was hot.<br /><br />Thanks for the help. We're going to use this thing to set lines up and down the Trinity river. Maybe a little lake running, too!<br /><br />Thanks,<br />Rob

 

[Fouled Plug]

Re: Mercury 9.8 question

The carb rebuild sounds like an excellent idea. Pumping the bulb and having no change virtually eliminates the fuel pump. Go with a thorough cleaning of the carb, and rebuild if necessary. I would replace the impeller as a precaution. They can take a "set" while stored and become much less efficent. It's cheap insurance! The intake for the cooling water should be at or below the cavitation plate on the lower unit. Look for slots or holes. How's the compression on this beast?

 

[robsd]

Re: Mercury 9.8 question

thanks for the reply Fouled..<br /><br />The compression seems quite good. I haven't put a gauge on it but you have to make an effort to pull it. I also forgot to mention the bulb and hose is pretty crispy. It had a couple leaks that I had to cut the end off, cut it back and push it back on. Also I feel something metal in the bulb. My in-laws 15hp seem to have an empty bulb, the check valve is just in one end. I plan on replacing this . Under the cover it looks like new even though he ran it in salt water sometimes.<br /><br />OK on the impeller, (I'm new to boat motors, not motors), the cavitation plate, that's the plate just above the prop? Correct? I first had the motor in a 5 gallon bucket filled with water, no coolant pumping. I filled a 30 gallon trash can and then got some water pumping(water about as deep as the clamps). Is the impeller itself down low near the intake? Sounds like an easy change? Yes? No? Maybe? Depends?<br /><br />Thanks Again,<br />Rob

 

[Fouled Plug]

Re: Mercury 9.8 question

Hmmm. Sounds like replacing the hose and primer bulb is mandatory. Fuel and/or air leaks are trouble. I have had success just taking the carb apart and cleaning it, needle and seat, and passages without buying a rebuild kit. Some are too far gone for this, though. Impeller is in a housing down near the cavitation plate. (Cav plate is where you think it is) You shouldn't have to have the motor that deep to make it pump...plan on replacing impeller as a precaution. It's not too challenging of a job, and with a manual and some familiarity with tools is easily within your grasp. You're into this thing so cheap (free) that spending a few bucks shouldn't be too painful! <br />

 

[robsd]

Re: Mercury 9.8 question

Thought I'd post a follow up in case anyone else has a simular problem.<br /><br />I replaced the bulb and hose, no help. I removed the carb and in doing so I had to remove the fuel pump. I blew on the vacumn hose and noticed a crack at the fitting. Hmmm maybe my bulb pumping wasn't enough to keep the fuel going. I just laid some sealer I had over the crack for a patch. Since I had the carb off I went ahead and took it apart. Pretty clean inside. The main jet in the bottom was about 3/4 clogged, you could still see daylight through it. The other removable brass jets were fine. I decided not to soak it in acid since I didn't have a kit and didn't want to swell any rubber. I also noticed the air adjustment screw was only 1/2 turn out. I set it to 1 1/4 turn. I read that here in another post..thanks! Put it back together and the thing ran great. I still need to replace the impeller. It just won't pump water unless you set it deep in water. <br /><br />I was also at a local discount sporting goods place here in Houston (Academy) and realized the deal I got. A small wheel trailer goes for $419, 16' Jon boat for about $500. A NEW 9.9 Mercury goes for $1649!!!! I understand these are new prices but WOW. It makes me apreciate it more.<br /><br />I do have a couple more questions. There is a hole just below the motor in the back. I believe yall are calling this the tell-tale?? What's supposed to come out of there. It looks like some water has come out of it. When water was pumping out of the small rubber tube on the side nothing was coming from this when I was running the motor. Also last question is there a gear oil on the lower end? I want to check this. I'm going to try to find a manual this weekend. Sorry for all the dumb questions.<br /><br />Thanks Again,<br />Rob