new bass boat engine troubles Mercury 115 misfiring with video

[taizer]

i just bought this boat. its a 1996 nitro 170tf with a 1996 mercury 115 2 cycle carb. the motor had a hard time starting but i let it sit then it started up fine and ran good. the weather is 40 outside and i have the water lines hooked up battery fully charged. here is what is happening

tI pump the fuel bulb till firm and then click the choke in once. i dont know if im suppose to hold the choke in with the key or clock it once. anyways the boat starts up after about 3 times cranking it. once started idles at 2000rpm as noted on tach. tach is very weird sometimes move sup and down randomly. tons of smoke from engine. this is the first time its running this year maybe because it was stored with oil in cylinders. but the engine warmed up and no more smoke. now the engine idles fine at 900rpm but if i give it a bit of gas throttle then it makes a popping noise at 1700rpm~. like it will run fine than randomly pop and bog out and i can see the engine smoke at that moment then it revives itself and runs fine then 2 seconds later it pops again. never runs smooth. im confused i know the engine is good since its intermittent.

i then change spark plugs and the old ones were covered i oil. i started with new plugs same thing.


heres the video. sorry on my iphone

http://s556.photobucket.com/albums/ss8/v8killaz/?action=view&current=IMG_0019-1.mp4

 

[SparkieBoat]

Re: new bass boat engine troubles Mercury 115 misfiring with video

maybe a fuel problem or something..check your spark and compression then clean your carbs good.

 

[CharlieB]

Re: new bass boat engine troubles Mercury 115 misfiring with video

Ditto, most probably needs the carbs cleaned.

Most carb motor tend to idle better when trimmed level, you may have to drop the nose of your trailer to get enough clearnace to trim down. That may help raise the fuel level in the carbs and fatten the idle mixture.

You have a 2 + 2, that is only the top two carbs have idle circuits, the lower two do not. The motor idles on only the top two cyl's. In your vid one cyl 'pops', engine speeds slows then slowly recovers. This may be caused by a 'lean miss', that cyl is not getting quite enough fuel to fire correctly, most often caused by a restricted idle fuel passage, they are pretty small and easily gummed up.

A service manual may be found thru the links in one of the 'sticky' posts at the top of this forum, read them, follow the links, download the appropriate manual for your motor. Study the section on Fuel. Clean your carbs then adjust them exactly as spelled out.

Repost any problems or requests for further clarification.

 

[taizer]

Re: new bass boat engine troubles Mercury 115 misfiring with video

ok so only the top 2 cylinders are working/firing at idle. i see. so the idle mixture is completely different then the wot or medium load mixtures.

can it be caused by old gas or no. i dont think so. the gas had stabil in it. ill check spark and compression when weather permits. can i check spark by just taking out the plugs and grounding them like you would do on a car. or does it have to be more specific. i have a compression tester i can do tomorrow.

and what about spraying the carbs with carb cleaner and then letting it dry. in my atv id spray a bit of carb cleaner followed by wd40. how hard is it to work on these carbs anyways. can i clean the carbs without taking them apart. like soaking it in some light duty solvent or wd40. maybe even gas

 

[CharlieB]

Re: new bass boat engine troubles Mercury 115 misfiring with video

A carb is a carb is a carb.

The major difference between your boat and an ATV or anything else, is your boat motor is working its butt off, all the time, while an ATV or car is only working hard on WOT acceleration. Any lean condition on a boat will melt a piston VERY quickly.

Cleaning, float settings, are the same. Idle mixtures on a two stroke is just like a weed wacker, the idle has to be fatter than best idle to provide the additional fuel for the motor to accelerate on throttle opening.

Spark MUST be hot enough to make a fat blue arc across a 7/16 gap or it will fail and misfire at WOT under load. It bites much harder than a weed wacker or lawn mower!

Check these links and get a copy of your service manual.

http://forums.iboats.com/showthread.php?t=309079&p=2072211#post2072211

http://1manual.com/Mercury manuals/Service_Manual_Index.html

 

[taizer]

Re: new bass boat engine troubles Mercury 115 misfiring with video

everything seems pretty simple it just needs getting used to

im looking at this right now to clean carbs anything i should looks for
http://1manual.com/Mercury manuals/Service Manual PDFs/TwoStroke/13645_2/3a.pdf

 

[The_Kid]

Re: new bass boat engine troubles Mercury 115 misfiring with video

and what about spraying the carbs with carb cleaner and then letting it dry. in my atv id spray a bit of carb cleaner followed by wd40. how hard is it to work on these carbs anyways. can i clean the carbs without taking them apart. like soaking it in some light duty solvent or wd40. maybe even gas

Just spraying carb cleaner is not going to get them clean where it counts. The hardest part to taking them apart is just getting the lower carb off the engine. The studs that hold the lower carb have to be removed because the lower cowl is so close the carb won't slide off the studs. If you're lucky the studs will come out of the intake manifold along with the nut. When I rebuilt the carbs on my 95 115, the nuts came loose and I had to remove the studs with vice grips. I kept the linkage and hoses connected between the carbs and removed all 4 as a unit. Once on the workbench I separated them one at a time to do the cleaning.

I picked up one of the gallon cans of cleaner that comes with a dip tray at one of the local auto parts stores. Even with the carb disassembled and soaking for over 24 hours I still had to uses a small brush to get rid of some buildup around the jets. I also ran a thin wire through all the orifices and blew everything out with an air gun.

 

[taizer]

Re: new bass boat engine troubles Mercury 115 misfiring with video

hey guy i open the intake cover and their is no filter is this normal. and their is a ton of oily residue all over the place. heres some pictures.

when i took the cover off it was full of oil and leaking out

 

[SparkieBoat]

Re: new bass boat engine troubles Mercury 115 misfiring with video

you probably have a stuck needle valve in that carb. does fuel squirt out of it when you pump up the bulb?

 

[The_Kid]

Re: new bass boat engine troubles Mercury 115 misfiring with video

No filter is normal. Mine had some oil residue but not as much as yours. When you tilt the engine up some of the oil/gas mixture may run out of the carb. The gas evaporates but the oil doesn't. When the engine misses it may also be blowing some of the gas/oil mixture back into the air box.