7.5 mercury

[CHARLES LEANDERSONE]

Hi<br /> i did like you said and i decorboned my motor with sea foam, changed my plugs put new gas in tank <br /> took to the river stared on 2ed pull ran wide open for 3 mile i use a gps slowed down to an idle ran fine then wanted to go fast again and motor ran like it was flooded i move the handle back and forward giving to gas then slowing it down then all of a sudden it takes off and runs great.<br /> let of the gas and it does it all over again.<br />took carb apart gaskets look ok, carb is clean <br />can anyone tell me if were to go now.<br /><br />thanks chuck

 

[12Footer]

Re: 7.5 mercury

Did you change the plugs? Sometimes, the decarbon cleaner does a number on the plugs. Also, here is a re-print of a recent reply to a simular problem. I hope it helps.;<br /><br />Take the pickup tube out of the gas tank.<br />Run compressed air thru it. If you can't,see if there is a ball (check valve inside the fitting at the top of the tube. If there is, remove it,and throw it as far away as you can.<br />But seeing as you have already eliminated carb as the problem, it has to be delivery TO the carb, IE; primer bulb, fuel pump,anti-siphon check ball in tank, inline and/or pump filter,or venting of gas tank.<br />To check for venting problem, loosen gas cap while under way. If performance returns, you nailed the problem.<br />Hope u find it. I know it gets agrivating.

 

[12Footer]

Re: 7.5 mercury

oops..Gotcha on the plugs...Brain rust on this end, sorry

 

[qbwebster]

Re: 7.5 mercury

Hello Charles<br /><br />Did you solve your problem?<br />I have exactly the same symptoms on a brand new 15hp Mercury 2002 model (built July '01)<br />Started second pull when cold on 25:1 break-in mixture and ran well at 2/3 to 3/4 throttle for an hour or so without slowing down.<br />When I idled for around 20 seconds and put into gear and increased throttle again it died at about 1/2 throttle. Tried increasing throttle slowly and quickly but no difference, engine would just choke and die.<br />Ran along at 1/4 throttle (on 1 Cyl. I think)and after about 60 seconds it sprang to life and ran well again but as soon as you go back to idle for more than about 10 seconds the problem repeats all over again.<br />I have had many small outboards and run them in on 25:1 mixture with no problems and I cannot believe the plugs would foul in only 10 to 20 seconds of idling.<br />Also the problem only occurs once the engine has warmed up and is under load.<br />Fuel is fresh 98 octane unleaded and oil is fresh Quicksilver so I do not see a problem there.<br />I am puzzled and disappointed with the new motor.<br />Any ideas would be most appreciated.<br /><br />Thanks QB

 

[Rex]

Re: 7.5 mercury

IF IT WAS A PICK UP PROBLEM WOULD THE CHOKE <br />HELP TO SEE. I WOULD DO THE SAME THING<br />WITH THE CHECK BALL.<br />I JUST TOLD QB TO CHECK THE IDLE JET AND <br />CHANGE PLUGS AT 25 TO 1 I COULD SEE WHERE A<br />PLUG COULD LOADUP<br />I HOPE SOME ONE GOT RIGHT<br />GOOD LUCK

 

[12Footer]

Re: 7.5 mercury

Hi again, Chuck . I have a Merc 7.5 that has a very intense ignition system on it. It'll throw an arc a full inch thru dry air! Not that I would let it do that,mind you (running it with a plug wire dangling in the air is a sure fire way of killing these "Thunderbolt ignitions").<br />But in spite of that (or maybee BECAUSE of that) , I burn out the plugs in less than 60hours. From what I have read,this is not uncommon,and most owner's manuals even sugest changing plugs at 60-80hour intervals under extreme conditions..Such as long term idling. One other caution on plugs.Stick with make/number plugs recommended. Do not use splitfire or goldie-platnum super duper 10buk each plugs,even if thier book shows a cross refference.<br />The reason for that little pearl of advice is,another type/heat range/make plug can burn a hole in a piston.<br />Next time the motor pulls that stunt on you (bogging down), reach over and give the primer bulb a couple pumps. I suspect a leak in the fuel line, probably at the fitting threads if it is new hose, which is leaking-down as you sit there. it starves for fuel for a short time, then picks it up,and off you go..This is just a theory at this point tho. But if a pump on the primer fixes the symptom, it's either that, plugged pick up in the carb or fuel tank, or fuel pump.<br />They're great little motors tho.

 

[12Footer]

Re: 7.5 mercury

QB, I think your plugs are fouling. Buy an extra set, and bring along an old spark plug wrench (in case you drop it,you aint lost much). I carry an extra set on both my boats along with the tools I think would get me out of trouble. I have had to change out plugs on the water due to fouling before. 2cycle engines go thru plugs like candy. A fouled plug means better than average lubrication, in my book. My bro is in the landscaping buisness,and burns 32:1 in ALL his 2cycle equipment. He also keeps a full compliment of spare plugs in the field,and decarbs everything once a week. I would decarb after breakin,and every 80hours after that.<br />butanyway... Good luck with,and long live the new engine.