Suzuki DT115 Skipping

Knightgang · Nov 1, 2003

I have a '85 Suzuki DT115. Out it in the water today, and had significant trouble cranking, not the first time. After it had run about 8 to ten minutes, it started skipping. Could not get WOT. Normally I can get the boat to run about 38 MPH, today was no more than 27, skipping the whole time. I first thought that it was starving for fuel, but determined that is not the case. Plugs are new, only about 1 1/2 hours on them and they still look good. Brought boat home and tried to trouble shoot. Cranked up motor, and began pulling plug wires on at the time. Number 1 & 2 caused the motor to go crazy when pulled, they should be okay. Number 3 wire shocked me through the insulation, and there was some change but not much when pulled. Number 4 had no change when the wire was pulled, but the wire bit me teriibly when I tried to put it back on. Does this sound like bad spark plug wires or ignition coils? Can the wires alone be replaced, or do they ome as part of the coil package ( and both have to be replaced?) I am trying to start problem solving taking the least expensive route first. If the wires alone can be replaced, do they have to be Suzuki, or can any generic model be used as long as the fittings connect? Any help would be appreciated. Thanks ---- Knightgang

DJ · Nov 1, 2003

Re: Suzuki DT115 Skipping

Knightgang, I had a DT-140 of the same year. It is basically the same engine. The Mikuni carbs are fine, but sensative. Most Suzi problems are carb. related, the electronics are pretty solid.. A thorough cleaning of all four is probably needed. Good news, is that they are very easy to dismount and clean.

Knightgang · Nov 2, 2003

Re: Suzuki DT115 Skipping

What about the Plug wire pull test, does that not really meen anything electrical? I am a bit of a shade tree auto mechanic, and I always understood that if you get shocked thru the insulation of a plug wire, then the wire needs to be replaced. Does this hold true on marine engines? Back to your carb idea, are you suggesting just a general cleaning, or a rebuild? Do I need to get a rebuild kit before I start? Am I looking for anything specific (broken reed, gummed jets, etc.) or just general ceaning if the jets, floats, butterflys and floats? I have never been into marine carbs, but I understand the basic from auto carbs and small engine carbs. Thanks for you input and please advise further. I hate to start something with only have the needed information. It just causes trouble and more frustration than needed. Knightgang

DJ · Nov 2, 2003

Re: Suzuki DT115 Skipping

Knightgang, Your spark plug wire test is merely telling you if that cylinder is working or not. To work, the cylinder needs fuel, spark and compression. I would remove the carburetors and install new kits. The Mikuni's are very simple. But, before that, do a compression test to make sure the basic engine is healthy.

rodbolt · Nov 2, 2003

Re: Suzuki DT115 Skipping

Hello listen to DJohns. but in the future use a spark tester. not only is the electrical on suzuki rock solid but very expensive. once the primary coil voltage fires the secondary will build to over 30 kilo(thousand) volts. with no other distibuter compents to arc to it will try to burn holes through the coils, backfeed CDI's and all kinds of other nasties. you have enough problems without creating more. I wish I had a dollar for every rectifier/regulator that I have replaced because the customer used the old pull the positive cable to see if it will die. the engine usually wont but the charging system usually will. try not to use many backyard auto tricks on this engine. the factory service manual for this engine is rather sketchy so in this case I would reccomend a clymer. good luck and keep posting

Knightgang · Nov 2, 2003

Re: Suzuki DT115 Skipping

Thanks for the info Rod. I actually read ( after I tried thr pull wires trick) that we should not do it that way. BTW, what components come in a carb rebuild kit? Looking at the CLymer manual, there is not much in side the carb to replace, other than the float, needle and a jet or two. I supose it has the remounting gaskets as well. I will call to order a kit tomorrow, and get the rebuild done as soon as possible. Once complete and tested, I will let you know how it went. Thanks for the input. Knightgang

DJ · Nov 2, 2003

Re: Suzuki DT115 Skipping

Knightgang, The carb kits are simple, as you suggest. It's a very straightforward design.

Knightgang · Nov 3, 2003

Re: Suzuki DT115 Skipping

Rod, Got carb kits and fuel pump diaphrams on the way. Got to thinking and came up with a question. How do you know if a cylinder is not contributing it you should nto remove the plug wire to listen for a change? I got a CLymer manual, but did not see anything about testing for cylinder contribution. Did I miss something? Thanks Rod, do you work on all outboards? Knightgang

Knightgang · Nov 8, 2003

Re: Suzuki DT115 Skipping

Okay, got the carbs rebuilt, and the fuel pump. They did not look to be that bad, but I figure it is worth it to go ahead and go through them. Put the boat in the water today, and the skipping is still there, although not quite as bad as it was before. While testing in the driveway, I tried to put a Spark Plug tester on it and number 3 plug wire was arking to the sparkplug tester thru the insulation with the tester still about 3/4 of an inch away from the wire. Is it possible that part of this skipping problem could be electrical???? Bad coil packs or at the least bad wires????? I am going to pull the coils packs off one at a time a test them for resistance according to the manual. I will let you know how it goes. Thanks for the help guys.

Knightgang · Nov 9, 2003

Re: Suzuki DT115 Skipping

Okay, pulled the coils today and tested with a multimeter. According to the manual, the resistance specs are as follows: Primary 0.2 - 0.5 (CDI connection lead to coil) Secondary 4,700 - 7,000 (Coil to Plug boot connection) My multi meter settings are 200, 2K, 20K, 200K, 2M. I used 200 for primary and 200K for secondary and got the following numbers: Primary Secondary #1 1.2 33.1 #2 1.2 11.6 #3 1.2 nothing (found broken connections in the plug boot) #4 .8 12.8 I am no electrical expert, but seeign that I got no two set of readings exactly the same, I would say that I need to replace my coils. Could someone else please interpret my test results base on the specs and the settings that I used and verify my conclusion. Thanks -- Knightgang

Knightgang · Nov 10, 2003

Re: Suzuki DT115 Skipping

Hi, Just got off the phone with Brown's Point Marin in NJ. I went over the readings with them and they said that everything checked out okay, except for the #3 that had the borken part in the plug cap. He instructed me to remove the cap from the wire by unscrewing it. Then test continuity from just the wire to the coil. That checked out okay, and he said that you can just replace the caps on these coils. (I did not know that.) That just goes to show you that nothing you learn on cars transfers over the outboards. I did not beleive it until now. I got 4 new plug caps on the way, and we will test again next weekend. Knightgang

Knightgang · Nov 12, 2003

Re: Suzuki DT115 Skipping

Thought you guys might like to know that after I pulled off the wire caps and trimmed the end of the wires to get to the good wire inside, I did another ohms test on the coils. Every one gave the same reading and they were very close to the manual's specs. Brown's Point said that they were close enought that they did not need to be replaced at the tune of $75 per coil. Hope this helps someone else. Knightgang

Knightgang · Nov 18, 2003

Re: Suzuki DT115 Skipping

Got the spark plug caps in yesterday and put on the wires and reinstalled coil packs. The boat has been sitting for a little over a week. After re-installing the coils, priming the bulb and having adjusted the choke linkage during the carb rebuild, she fired up on the hose better than any other time after sitting a week and I only used on battery, not both as usual. I guess I should not throw out all of my knowledge from cars, just most of it. I initially thought that the skipping was electrical, but I had no idea that it would be "Spark Plug Caps". Guess these things are engineering marvels of their own kind. I will test this saturday, earlier if possible, but I will not hold my breath. Knightgang

Suzuki DT115 Skipping

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