1968 Mercury 110 (9.8) flooding on idle - any idea why?

[Mastiff_in_Norway]

I'm driven to madness by this old engine. My 78 year old father has a wooden boat which I figured needed a period engine. So we found this, which turned out to be a right lemon, compared to what the seller said. Unfortunately we found that out a bit late, so no point i trying to get anythingback. "Sold as is". The powerhead has been dismantled, so the bottom of the crank casing seals properly. The crank has been replaced, so it works pretty well. And with a bit of help here from the forum we found that one coil was damaged (acting up when it got warm), so that's now replaced. Everything works, except for that the engine still isn't useable because it won't run on anything close to idle. I have a boat mechanic who helps me (neighbour's son, or I'd be bankrupt by now...). He's a wizzard with engines (five years ago when he took is final test after his apprenticeship he was voted the best apprentice in the county, in all diciplins!) but this one has him a bit stumped. Can anybody give me a good reason why it should flood on idle, so it stops? He says it could help to get an exploded parts drawing of the motor, but I haven't been able to find a good one, they are usually faint and low resolution. So help would be appreciated, both with finding a good drawing and even more with sound ideas to why this is happening.

 

[60sboater]

I have not worked on one of those old carbs. I'd guess maybe a heavy float or needle/seat problem. You might want to join JohnsOldMercurySite.com if you don't find an answer here. There are guys who have many old 9.8s as well as many other types(illustrations too). I hope you stick with it because you will be very happy to get it running well.

I think it has a cork float. Parts are available and maybe a spare carb from ebay would help. Has your friend gone through the carb yet?

 

[Mastiff_in_Norway]

Thanks for answering! I have sunk far, far, FAR too much time, worry and money into this thing to give it up now! :joyous: So I have registered at the site you mention, and I'll post there when my membership comes through. It's slow going, for some reason.

The carb has been gone through 3 times before, and it's now in pieces awaiting advice, drawings or anything that can help. If possible I would like to fix this without buying parts from eBay, it sets the time back around 2 weeks every time. But we'll see what the OldMercury guys say.

 

[racerone]

Why do you think it is flooding ?---What are the symptoms ?

 

[Mastiff_in_Norway]

Hi, thanks for answering! I have no idea. My mechanic said he's pretty sure that's what's happening when it stops after a short while on idle, and I forgot to ask him why he think so. I'll try to get hold of him and ask, he's difficult during weekends. :lol:

 

[merc850]

Here's the proper method for setting the needle/float; after you reinstall the carb run the engine at approx 1200 rpm in gear and adjust the low speed needle until the engine runs smoothly.

 

[Mastiff_in_Norway]

Thanks!

 

[Chinewalker]

Check the fuel pump diaphragm for pinholes. Might be sucking fuel right into the crankcase,flooding it out. At almost 50 years old, if it's still original it's likely brittle anyway...

 

[Mastiff_in_Norway]

Chinewalker, that diaphragm's been changed, and the gasket in the fuel pump.The fuel was flooding out of the carb, so it has to be something with the adjustment of the floater or even the floater itself.