# 115 Suzuki 4 Stroke - Idle Surge



## ecnadnus (Oct 23, 2009)

I have 2002 Suzuki 115 4 Stroke with about 450 hours on it that I purchased late last year. This year I probably put 125 hours on the motor and it runs absolutely great and I love the fuel mileage too. I do a lot of trolling with it and every once in a while, I'll get a throttle surge. 700 RPMs up to 950-1000 and then back down to 700. Sometimes it's just a quick jump and other times it will take 30-60 seconds to drop back. I ran SeaFoam in a couple tanks earlier in the year but really didnt notice a difference. Anybody have any ideas on whats causing this??

Thanks


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## peple of the perch (Sep 13, 2004)

Take out the spark plugs and inspect the piston heads and see if there is any carbon build up on the motor. If there is a build up I would suggest decarbing the motor. If the heads are clean I would recommend a carb clean. If Problems still occur than I you might have a faulty fuel pump. Does the motor run just fine other than the surging problem? How often does the surging occur?

"This works for Carbed, EFI, Ficht, HPDI, Opti-max and even 4-strokes... and should be administered after every 50-60 hours of use. First you need a separate small fuel tank. One of those 3-gallon red Tempos works well or an empty gallon milk jug in a pinch, but it might be a bit messier. I use Seafoam over the OEM (original equipment manufacturer) stuff like OMC Engine Tuner or Mercury Power Tune. Note: in the last few years they changed the formula and you have to let them sit up 12 hours. Who's got time for that? Seafoam does the job in 15 minutes and can be purchased from NAPA, Car Quest or other auto stores. You'll need 3/4 gallon of gasoline and one 16oz can of Seafoam for each engine. Don't forget to add 3oz of oil if you are pre-mixing in a carbed engine. Use a 3 ft piece of fuel hose off the small tank. Connect this tank to your engine by pulling off the main tank fuel hose from the intake side of your water separating fuel filter and plug the hose off the small tank onto that fitting. Or you can separate the fuel line on the tank side primer ball, so you can still use your primer. If your engine has a fuel plug then you will also need a fuel plug on the smaller tank's hose. Start the engine, let it warm up and start pulling the mix into the engine. You may have to increase the idle to keep it running once she gets loaded with the Seafoam. Run the engine 15 minutes at the dock or just cruising around under 2500 rpm's. Then shut it down and let it sit for another 15 minutes. Restart the engine; the smoke you see is the carbon burning off. Do the whole thing again and let her sit again for 15 more minutes. If she smokes after the second time do it again. I've never seen one still smoke after three doses. (I bought a Bronco two years ago that had 95,000 miles on it. When I used Seafoam on it I had the neighbors hanging out of their front doors looking for where the fire was after I started it the first time there so much smoke) The gallon mix should be just enough to do this 3 times. You don't need a wide-open throttle and you don't need to change the plugs. The plugs are cleaned at the same time as the combustion chambers. My suggestion is that every 50-60hrs is the optimal time to change plugs in most engines. I cleaned an antique Evinrude once that had a 1/4" of solid carbon on the exhaust chamber walls by running a 1/2 gal of the aforementioned mix through it. Seafoam, a great product, has been around since the 1930's and it's what they used when they were burning straight 4 stroke 40SAE oils in outboards. For you guys with the 4 stroke outboards? Those engines work 10 times as hard as any auto engine ever will and they too will carbon up. Too many are under the assumption that it's totally the 2 stroke oil that causes the carbon, Wrong... it's also the additives they put in the fuels today. The carbon inhibitors in 2-stroke oil are there for this reason also. Remember when gasoline used to smell like gasoline, today it smells more like bad cologne. For those guys that like to work the carbon treatment by spraying it down the carbs, Seafoam also comes in spray can called Deep Creep."


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## ecnadnus (Oct 23, 2009)

Thanks for a ll the detail. No it doesnt do it all the time and the engine runs just perfect other than the idle surge. Sometimes it wont do it at all and other times, it will happen 2-3 times on an outing.


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## CarpetBagger (Sep 21, 2009)

9 out of 10 times this has to do with fuel delivery...Check/replace primer ball, hoses, fittings, ect...If you are only experiencing the problem at idle I'd have to assume air leak somewhere is messing up the fuel delivery and causing the motor to speed up...

Im not 100% sure if this motor has a stage of fuel injection in it, but it could be a fuel pump problem as well....

You shouldnt have to decarb that motor...Suzuki makes a fairly sophisticated engine and Id change my spark plugs before I ran all that stuff through a perfectly good engine...


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## Benboat (Jan 20, 2008)

I have the same engine except its a 2001 model. I was having the exact same problem and found that the fuel feed hoses were deteriorated and loose on the fittings. I replaced the fuel feed hoses, primer ball, connector on the engine and all hose clamps and it solved the problem. Also replace your water separating fuel filter once a year. It definitely sounds like it is sucking air. There should also be a small fuel filter on the engine. The anti-siphon valve on the fuel tank could also be causing this. This engine has been great for me. Its amazing how little fuel it burns.


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