'77 Merc 1150 sometimes idles bad??

[headcopter]

Hi all, my Tower of Power 1150 '77 MERC sometimes idles bad (and may even stall), not all the time though, this is an occasional problem. Any thoughts??<br /><br />ERIN

 

[petryshyn]

Re: '77 Merc 1150 sometimes idles bad??

Oh what the heck, lets give it a go!! I think we need some answers first. Being intermittent, it can get quite involved.<br />- What temperature is the engine when its rough?<br />- Is there a lack of power if you get it up to speed?<br />- Does the engine smooth out when RPM is increased slightly (gearbox in nuetral)?<br />- When's the last time the carbs were done?<br />- Does the condition occur mostly when relative humidity is high?<br />- Have you attempted a idle mixture adjustment when rough?<br />- Is this only after a long period of storage?<br />- What tests have you performed on this engine?<br />- Do you have perma-gap plugs installed?<br />- What maintenance have you performed?<br />- What oil are you using....what mix ratio?<br />- Any visible rust in the tank?<br />- Does it act up only on initial start-up, or later on during your activities?<br /> All this otta help put us in the right direction.......

 

[headcopter]

Re: '77 Merc 1150 sometimes idles bad??

Hi Schematic, thanks!! OK here goes...<br /><br />- What temperature is the engine when its rough?...NOT SURE EXACTLY, BUT TELL TALE WATER IS HOT, NOT BURNING HOT, BUT HOT!<br /><br />- Is there a lack of power if you get it up to speed?...NO, POWER IS FINE!!<br /><br />- Does the engine smooth out when RPM is increased slightly (gearbox in nuetral)?...<br />YES!!<br /><br />- When's the last time the carbs were done?...CARBS WERE DONE RECENTLY JUST AFTER I BOUGHT IT. WAS STALLING AND THE BOAT YARD CLEANED ALL THE CARBS AND FUEL LINE!!<br /><br />- Does the condition occur mostly when relative humidity is high?...NO<br /><br />- Have you attempted a idle mixture adjustment when rough?.....NO. IS THIS SOMETHING I CAN DO MYSELF??<br /><br />- Is this only after a long period of storage?....NO, I USE IT MOST WEEKENDS FOR A FEW HOURS AT LEAST<br /><br />- What tests have you performed on this engine?...PERSONALLY NONE!!, BUT THE YARD I BOUGHT IT FROM ASSURED ME THAT IT HAS BEEN REGULARLY SERVICED FOR THE LAST 15 YEARS (SAME OWNER)<br /><br />- Do you have perma-gap plugs installed?...NOT SURE, HOW DO I TELL??<br /><br />- What maintenance have you performed?...FLUSH OUT WITH FRESH WATER FOR 15 MINUTES AFTER EACH USE AND SPRAY INSIDE WITH WD40 FOR COROSSION PROTECTION<br /><br />- What oil are you using....what mix ratio?...MARINE 2 STROKE, CAN'T TELL YOU RIGHT NOW, OIL IS IN BOAT (10:46PM HERE)<br /><br />- Any visible rust in the tank?...TANK HAS BEEN CHECKED....SQUEEKY CLEAN!!<br /><br />- Does it act up only on initial start-up, or later on during your activities?....INITIAL STARTUP IS OK USUALLY. DOESN'T LIKE THE COLD TOO MUCH, BUT IT IS USUALLY HAS PROBLEMS ONCE IT IS WARM!<br /><br />Thanks heaps for your help. I hope this information is enough. I am fairly new to all of this, but have a good mate that owns a mechanic shop that can help me with tricky stuff so I wont have to pay a boat spanner a small fortune!!<br /> <br />ERIN

 

[headcopter]

Re: '77 Merc 1150 sometimes idles bad??

Forgot to tell you the oil mix....50 : 1<br /><br />Cheers. ERIN

 

[JeffM]

Re: '77 Merc 1150 sometimes idles bad??

I can't wait to hear this answer, i have the identical problem with all the identical conditions with my 1975 1150!<br /><br />One peculiar thing I noticed with mine, but not sure if this is the cause of the rough idle and stalling, is that gas leaks out the lowest carb, especially when squeezing the priming bulb. I've been told here on this board that my float is stuck open. New carb job in the spring for me.<br /><br />So you're not sluggish out of the hole when you drop the throttle? Mine is at first, but as RPMs get higher engine pulls better.

 

[petryshyn]

Re: '77 Merc 1150 sometimes idles bad??

Headcopter ahoy:<br />Don't know any common problems that would cause this....maybe someone else does....and will help put us in the right direction.<br />If not, we'll continue:<br />AGAIN, being intermitent, it can get involved.<br /><br />This is a perma-gap plug<br />

<br />We have to get in the right direction. Can you get your mate to do a compression test? While he has the plugs out, compare their looks.<br />-when the boat yard did the carbs, did they adjust them on the engine afterwards?<br />-did it improve at all when they did the carbs?<br />-you say it doesn't like the cold too much. please clarify......<br />-is it hard starting when cold?<br />-how often does it idle poorly?<br />-how long will it idle poorly?<br />-does squeezing the primer bulb help when idling rough?<br />-next time it idles rough, slowly and gently place your hand over each carbs air inlet(one at a time) Does this cause an improvement on any one carb?<br />-do you feel any puffing on your hand at any carb?<br />-next time it idles 'fine', shut off, pull the top plug wire off ground the wire to the block. <br />Restart engine.<br />-Does this sound like the same type of rough idle?<br />-If we don't solve this by manipulating the fuel system, we'll move on to ignition. Ask your mate if he has a spark tester. (an adjustable air gap device that can be plugged into the plug wire and cliped to ground)<br />Click me<br />Some people make their own by using an old plug, but sometimes we need more gap.<br />This is way too much typing for a one fingered hunt and pecker....LoL<br />Good Daye<br />

 

[headcopter]

Re: '77 Merc 1150 sometimes idles bad??

Ahoy Schematic, sorry for taking so long to reply.....been away on business!!<br /><br />OK. here goes....<br /><br />- Compression is fine (can't remember exactly what, but my spanner said it was good on all six) Plugs look good!<br />- Not sure exactly what adjustment the yard did on the carbs, I'll aks them!!<br />- much improvement after they cleaned the fuel lines and did the carbs!!<br />- a bit hard to start and likes to warm up before it will idle smoothly!!<br />-idles poorly after about 30 minutes to an hour of solid use at around 4500RPM<br />- once hot, it will idle poorly until it cools down a bit!<br />-does squeezing the primer bulb help when idling rough? YES SOMETIMES, but I have replaced the bulb!!<br />- I'll go out with my spanner mate and follow your instructions and see what happens.<br /><br />Someone suggested it could be the mixture? Maybe that was you?? Anyway, I'll have it out again tomorrow and we'll see how it goes. Thanks for your help.<br /><br />Cheers. ERIN

 

[Bear]

Re: '77 Merc 1150 sometimes idles bad??

As OrangeCrushGT150 said: "One peculiar thing I noticed with mine, but not sure if this is the cause of the rough idle and stalling, is that gas leaks out the lowest carb, especially when squeezing the priming bulb. I've been told here on this board that my float is stuck open. New carb job in the spring for me."<br />I think cleaning or replacing the float valve will take care of your (OrangeCrushGT150) problem. Check if the float moves freely too.<br /><br />headcopter, I would check the sparkplug caps and ingition coils for rust or oxide too. If the length is ok, cut them 1/4 of an inch just to make shure. The engine is getting old so that is a good idea anyway even if it has nothing to do with your problem. (Nothing wrong with old...)<br /><br />When this rough idle occurs, did you ever check the colour of all sparkplugs? Is there a wet sparkplug? Have you replaced all sparkplugs lately? Can you tell if they are worn? <br />Do you have a working thermostat that opens and closes at the right temperatures? (Is there one on that engine at all? I don't know.)<br />Squeezing the new bulb at rough idle, does that make any difference? Might be a dirty or worn float valve in your carb too.<br />How about the air mixture screws? If you count and turn them carefully to the bottom it should be the same amount of turns on all carbs. If it is, say 1 1/8 turns,they should all be out 1 1/8 turns (check in the book). Then you can turn all out 1/8 turn more. Go back to 1 1/8 turns and turn all IN 1/8 turn.<br /><br />Please do one change at a time and then take it for a test run. That is important if you dont want to get lost. If you do the air mixture thing, you just have to start it up and listen.<br /><br />And please check with your friendly spanner or The Book about the amount of turns for the air screws. Someone here might know too.<br /><br />Just my two cents...<br /><br />Good luck and get back here soon <br /><br />/Bear

 

[petryshyn]

Re: '77 Merc 1150 sometimes idles bad??

Ditto bear.....<br /><br />headcopter, when I asked you to squeeze the primer bulb when idling poor, I was determining if:<br />- Fuel pump pressure low when idling?(squeezing bulb increases fuel pressure and fills low fuel bowls and improves lean idle)<br />- Is carb flooding? (Squeezing bulb increases fuel pressure and shows up weak float circuit)<br />- When you squeeze the bulb, you are acting as the fuel pump! <br /><br />- You say that after several minutes of 4500rpm operation it will idle poor. If you return immediately to 4500, does it perform OK?<br /><br />- After 30 min or so of operation, come to a stop and shut engine down....any fuel leaking out of any carb? as bear suggests<br /><br />- I don't remember seeing a thermostat in that engine. If there is one,(see your manual) it should be checked.(as per bear's suggestion)<br /><br />- If you are not sure what the yard did for adjustments, you may have to take it upon yourself to get a manual and set the carbs and timing. It is also possible that the switch box is also giving trouble when hot. Thats why I ask if it performs well at 4500 immediately after you've observed a poor idle condition.<br /><br />For your type of intermittent problem, it might save some hair pulling if you purchase a neon flash tube ignition indicator.(looks like a pen) I haven't seen one in the stores for awhile, but I'll search for one on the net.(I believe champion made them)This tool gives you a visual indication of required spark plug voltage without pulling off the wire. If you have an intermittent spark, its easy to see.(a very useful and unknown tool) If anyone has seen one for sale, let us know!! It would be to your advantage to have one of these tools along with a spark tester. Lets answer all the questions before we continue.....