'74 Mercury 650 dies when put into gear - timing? Idle adjustments?

[jthompsonff]

I recently traded for a 74 mercury 650 3 cyl. I have so far had to clean the carbs out thoroughly, replace the mercury switch and put something in the distributor in place of the carbon and spring. I also had to turn the screw for the timing advance all the way out to get it to idle smoothly (which it does! although seems to high to me, not sure what RPMs I need to be at). I took it out and put it in the lake and as soon as I put it in gear it died. I was able to get it started using the choke and then it seemed to take off okay, but I think it could be a little more responsive and have a little more power. I do have to replace the impeller (Ihope that is the problem) as it has a weak telltale and steam comes out the other side (vent?). think I may be getting exhaust leaking into the lower unit heating the water before it get's up to the engine. the engine warms up quick and then (Iam pretty sure based on the leftover oil sludge build up in the carb bowls) evaporates, or "boils" the fuel mixture. so hopefully impeller will solve this problem as everything I have found to flush and blow through seems to be free of debri or obstruction. Sorry, I got off point a little bit there... wondering if the engine not sustaining an idle with the boat in gear could be timing since I have to have it all the way back (the screw out as far as the rubber stopper will let it go) or if it's more an idle screw issue and then I can turn that timing adjustment screw back in and sustain a better, lower idle? sorry guys, I know this is a long post, but I am excited to get this baby running at top performance after what work I have already done.

 

[mongose2]

Re: '74 Mercury 650 dies when put into gear - timing? Idle adjustments?

i recently traded for a 74 mercury 650 3 cyl. I have so far had to clean the carbs out thoroughly, replace the mercury switch and put something in the distributor in place of the carbon and spring. I also had to turn the screw for the timing advance all the way out to get it to idle smoothly (which it does! Although seems to high to me, not sure what rpms i need to be at).

First off, get a mercury shop manule for your motor. It'll cost you about 20 bucks and will save you much more in a short period of time.
I took it out and put it in the lake and as soon as i put it in gear it died. I was able to get it started using the choke and then it seemed to take off okay, but i think it could be a little more responsive and have a little more power.

I do have to replace the impeller (ihope that is the problem) as it has a weak telltale and steam comes out the other side (vent?).
Second, the water pump should have been the first thing you replaced.

Think i may be getting exhaust leaking into the lower unit heating the water before it get's up to the engine. Check the fluid in the lower unit to see if it's brown. If so, it's got water in it, but it probably isn't from the exhaust.
The engine warms up quick and then (iam pretty sure based on the leftover oil sludge build up in the carb bowls) evaporates, or "boils" the fuel mixture. So hopefully impeller will solve this problem as everything i have found to flush and blow through seems to be free of debri or obstruction.
The engine will probably freeze before it gets hot enough to evaporate the gas and leave oil. Get rid of any old gas/oil mix, clean tubing again, clean carb bowls, and try new. On that motor it's advisary to always run the engine until the gas is burned up after disconnecting the gas line.
Sorry, i got off point a little bit there... Wondering if the engine not sustaining an idle with the boat in gear could be timing since i have to have it all the way back (the screw out as far as the rubber stopper will let it go) or if it's more an idle screw issue and then i can turn that timing adjustment screw back in and sustain a better, lower idle? Sorry guys, i know this is a long post, but i am excited to get this baby running at top performance after what work i have already done.

you can't adjust the timming without a timming light and get it right. I remember running the older merchs in high school and after and they could be a bear if you don't do it right. I now have a 23 year old 1989 115 hp, and it was down for almost a year before some of the guys on this "station" helped me out. Mine would run great on the hose, but would die when put in gear in the water. I must have adjusted everything on it at least a dozen times, cleaned the injectors, tubing carbs, everything. Didn't help. Then in the very back of the manule, was: How to set up the remote control for this engine. Had done it many times before from "feeling" it, but did it right, and now she runs like a scaulded jackass at 55mph and will idle all day without sputtering. Hope you get the help you need to use it this summer.....mongose