71 Merc 650 hard starting, flat spot

[aredant]

I just got this engine last week and have been working out all the bugs. It's a nice motor, but it's built like a chinese puzzle box. Maybe the carbs need work - they are buried in the middle of everything.<br /><br />out of water started ran great! (begged my norwegian bachelor drummer friend to take her out with me)<br /><br />In water:<br />1. Starts great cold after initial prime.<br />2. Idles fine but was sluggish accellerating.<br />3. Ran great when warmed up.<br />4. Hard to start after sitting a bit, bulb soft.<br />5. Hard start. Have to prime and hit choke.<br />5. Once started, idles but dies when accelerating unless it warms up.<br /><br />New gas tank and external line, fuel pump check valves, diaphragm, gasket seem fine. Compression, ignition system good. I'm wrenched out this week - don't wanna extract the carbs.<br />Any ideas?

 

[mellowyellow]

Re: 71 Merc 650 hard starting, flat spot

try a new primer bulb first...system should not<br />lose prime. when accelerating, have someone pump<br />the bulb and see if she picks up.<br />good luck,<br />M.Y.

 

[corm]

Re: 71 Merc 650 hard starting, flat spot

Hi,<br />My guess would be that your carbs are set to lean.<br />Enrichen the idle needle 1/8 of a turn on each and try it again. It never takes more that 1/4 turn out to solve acceleration problems. Most peeps set the carbs to lean on Merc's for the best idle. You need to set them a bit rich for best take off. It will start better too. For the hard starting after sitting that could be the quality of fuel these days. It can boil out of the carb bowl after you shut off the motor, so you need to squeeze the primer bulb to refill the carbs.

 

[aredant]

Re: 71 Merc 650 hard starting, flat spot

First of all, thanks so much for your prompt replies!<br /><br />Corm, I threw the boat in the river tonight to do some troubleshooting. Starting was very difficult and I noticed that the bottom carb leaked alot when I primed the system, I finally got it started and warm it up and adjusted the mixture screws with engine in gear. You are right on - about a 1/4 turn rich and starting and accelleration was greatly improved! Bottom carb seemed to stop leaking after warm up. Perhaps the float valve is leaky on the bottom carb?<br /><br />I'll bring a spare bulb with on the next outing and try that too. It takes a solid fishing session to bring out all the bugs.<br /><br />Whats a peep?

 

[corm]

Re: 71 Merc 650 hard starting, flat spot

Hi,<br />It sounds like the needle & seat may be getting old. Common on a 71. hehe Glad it is taking off better. You may want to rebuild the carbs on her when it gets a little cooler and your not using it so much if it lets you waint that long. Sorry about the peeps thing.Peeps is a slang term for people in the Quake 3 world. I play the game online alot. So I forget to try and not use slang on other message boards. Frank Black is my gaming name if you play.

 

[aredant]

Re: 71 Merc 650 hard starting, flat spot

Corm,<br /><br />Boat ran beautifully on today's fishing outing. Sometimes things are simpler than you might think.<br /><br />I used to play Quake alot and other vids, but I am 40 now and nowadays my hands ache, my eyes get tired and I get dizzy when I play shooters - I can deal with Mechwarrior, though.<br /><br />Thanks again,<br /><br />The Ant