TOPIC: 1964 Merc 650 - rebuilding carbs

Had this problem last year... some Seafoam seemed to help. But this year not quite.

Motor starts up fine cold, cruises fine, etc. Find a spot in the lake, kill the engine. Anytime within the next hour the only way I can get the motor started is putting it WOT in gear which I'm guessing is not good for the motor. Also, while the engine is warm, it idles rough and stalls.

I'm guessing it's a problem with the carbs. In the 4 years I've had the boat, I've never done any work to them, other than tweaking the idle and fuel/air mixtures.

Want to pull the carbs off, disassemble and clean them this week. I've done this plenty of times on small engines (i.e., power lawn equipment, etc...), but never on a Merc.

Is it pretty much the same deal, or a different beast on an old Merc like mine? Any tips, pointers, gotchas, etc... I need to be aware of?

Thanks.

Hope this works.... web.ebscohost.com/serrc/pdf?sid=4759c207-47e2-46c0-a3e2-e0b5eff1c66b%40sessionmgr15&vid=4&hid=18

Yay!!! It worked!!!! Your Tillotson looks pretty straightforward, and you get more basic info to boot.

Perfect - many thanks!!

Started this tonight... got the starter off. I take it I gotta take the distributor off as well? Should be straight-forward correct? Looking at the manual someone sent me - is there more than just a few bolts off the crank case and the timing pulley? What about putting it back on and timing?

Tips, pointers? I don't mind learning this stuff, but on the other hand I don't want to get too far in over my head with this either.

Seems like a lot of work just to pull the carbs...

Nessman
You can do it. It is all pretty straightforward.
If you have a digital camera, take pics as you go. Keep referring to your manual and posting here.
It is just a 2-stroke motor.
Pretty much three systems.
Mechanical-block/crank/pistons/etc.
Electrical--Stator/wires/dist./starter/etc
Fuel--Fuel pumps/carbs./etc.
Take your time and learn as you go.
When you go back together with everything and you fire it up, you can stand back and say "I did that". One of the best feelings in the world.
I am not trying to come off as a coach or cheerleader here, I am just thinking of when I first pulled the cowl on my first motor and thought, "Oh man, what did I do, this ain't gonna be good".
But I made it through and you will too. Dive in man, the waters fine.
Neil

Thanks - appreciate the encouragement. I'm sure I can do it - just want to try to get the distributor off with as few headaches as possible.

Just dive in! Like Neil said. I dove in my Homelite and redid the valve clearance and changed a cam twice! It was scary, but I did it. And it runs great today. I can stand back and say I did it!. So can you!

I pulled the carbs off my Merc700 without removing the distributor, but in "hind-sight" it would have been easier! I just unhooked the linkage so I could turn the dist. for maximum clearance, but it was still a bugger. LOL

thanks for the service manual. i'll never use it but my mechanic will. ron

OK - so had to pull the flywheel, starter and distributor. Not so bad getting it all off - just everything's in cramped quarters. Putting it back together shouldn't be too bad - took pictures beforehand to help me out if I get stuck with the reassembly, but seems pretty straightforward.

Carbs weren't in bad shape - expected worse, bowls had a little bit of gunk in them and everything got a good cleaning with gumout. But I did notice the strainer cover on the bottom carb was loose which may explain some of the problems I was having.

Should have everything back together tomorrow night or Saturday and hopefully I'll be back in the water this weekend!

Carbs cleaned up and ready to go...


Flywheel, distributor and starter removed to access carbs...

It's time consuming but kinda cool how it is all tucked in there.
Pretty basic stuff though, right?
Glad you made it through and I hope she runs well for you.
Neil

Everything's put back together and up and running. Started right up. Let it sit for a while, fires right back up this time. Thanks again for everyone's help. As some of you have said - it's not that hard once you know what you're doing - given this was my first time doing this kind of work on a Merc, I'd say it was a success - with you guys getting much of the credit.

Some video of its first run:



Couple of questions - I'm not having to choke the engine at all to start it. Idle speed is a bit high, maybe it's a moot point once it's in the water - but the idle stop screw is backed off all the way. Mixture screws are both one full turn out.

Anything else I need to be paying attention to?

good job on the timing and carb rebuild!

not good to run them so high rpm on the muffs.....

check to see that the linkage or cables are not preventing the butterflys to close correctly & return to the idle position...check the sync linkage between the carbs to make sure they correct

is there a return spring on the mag that helps to return to idle

once in the water re-adjust the idle mix screws while in gear

Had to adjust the throttle cable from the control box - was too loose causing some play on the magnetos. Now idling at a lower speed and.

Getting some surging at idle now. Fuel pump(s) perhaps - bad diaphragm(s)? Was gonna take it out on the lake this afternoon, but gotta go out for my mother-in-law's birthday dinner (miss that and I'm dead!). Gonna be nice tomorrow and got the entire day.

Butterflies are lined up and closed at idle - so no problem there.