Suzuki DT 30, 2004 Ignition coil

[Polycraft]

I have given this a new title. After looking into possible vapour lock/ heat sink the motor still stalls when I put in in gear, after a long run. I heard bad ignition coils can be a common problem. Also at the previous service the mechanic put the wrong spark plugs in and I have heard this can damage the coil. Would one of those spark plug testers with a flashing light be a good way to test the coil? I would probably have to do it on the water after a long run. Or if it's a cheap part I might just swap it out by way of elimination. Any other suggestions - it goes like the clappers the rest of the time?

[Murray]

You can test coils by measuring the resistance. If I’m not mistaken you have a primary and secondary circuits to test. Google will tell you the how to test the coils. I have no idea what the resistance should be, those numbers and procedure will be in your service manual. Another thought is test all 3 coils and compare the resistance, if one is different than the other two than thats likely your culprit. When your engine starts acting up you could pull one plug wire at a time and see if your engine performance changes, my thinking is if you plug a plug wire that is attached to a faulty coil then you should notice no change to the engine. Disclaimer, I’m no expert on engine electrical systems so I’m hoping other forum members will chine in and support or refute my comments.

[Polycraft]

You can test coils by measuring the resistance. If I’m not mistaken you have a primary and secondary circuits to test. Google will tell you the how to test the coils. I have no idea what the resistance should be, those numbers and procedure will be in your service manual. Another thought is test all 3 coils and compare the resistance, if one is different than the other two than thats likely your culprit. When your engine starts acting up you could pull one plug wire at a time and see if your engine performance changes, my thinking is if you plug a plug wire that is attached to a faulty coil then you should notice no change to the engine. Disclaimer, I’m no expert on engine electrical systems so I’m hoping other forum members will chine in and support or refute my comments.

Thanks for that. It only has one coil with 2 spark plug leads coming off from memory. It's called the drop test what you described. The trouble is it only plays up when I put it in gear - stalls. This will likely happen in any case if I drop one cylinder. Perhaps I might hear a change in idle and it might identify a faulty spark plug.

[Murray]

https://www.boats.net/catalog/suzuki.../ignition-coil

2004 DT30 shows 3 as quantity unless I’m missing something?

[Polycraft]

https://www.boats.net/catalog/suzuki.../ignition-coil

2004 DT30 shows 3 as quantity unless I’m missing something?

Well that's a DF not a DT. Plus the DT only has 2 cylinders so you wouldn't have 3 coils. The DF is a 4 stroke I think, whereas the DT is a 2 stroke.

[Murray]

My apologies, I read from post #1 “DT 30, 2004 Ignition Coil”, went over to the parts page and didn’t really look closely that the parts I linked to was a DF30. So I go back to the parts page for 30hp and look for the DT model, none listed. You are correct re DT 2 stroke and DF 4 stroke, parts page said 3 coils so I went with that. What engine and year do you have?

[Polycraft]

My apologies, I read from post #1 “DT 30, 2004 Ignition Coil”, went over to the parts page and didn’t really look closely that the parts I linked to was a DF30. So I go back to the parts page for 30hp and look for the DT model, none listed. You are correct re DT 2 stroke and DF 4 stroke, parts page said 3 coils so I went with that. What engine and year do you have?

DT30, 2004, as in the title.

[Murray]

In 2004 Suzuki DID NOT make a DT model. If you have a 2004 it is not a 2 stroke. If you have a DT 30 then it’s not 2004. According to the “Buy Suzuki Outboard Parts” (top of this page) 1997 was the last year Suzuki made a 2 stroke 30hp. First thing we need to do is figure out what engine and year you really have. On the clamp bracket there should be a metal tag with model (DT or DF with a number representing the hp) and a serial number. Please check.

[Polycraft]

In 2004 Suzuki DID NOT make a DT model. If you have a 2004 it is not a 2 stroke. If you have a DT 30 then it’s not 2004. According to the “Buy Suzuki Outboard Parts” (top of this page) 1997 was the last year Suzuki made a 2 stroke 30hp. First thing we need to do is figure out what engine and year you really have. On the clamp bracket there should be a metal tag with model (DT or DF with a number representing the hp) and a serial number. Please check.

It's definitely a 2 stroke and I bought it brand new in 2005. In Australia by the way - maybe they just weren't sold in the US after 1997 and your parts list reflects that.

[Murray]

Interesting, I didn’t know that. Post #2 still holds, If it was me I’d still check the coils with a resistance test, cheaper than replacing what could be a good coil(s). Your issues may not be coil(s). Can’t speak for the plug tester you refer to in post #1, never used one. Speaking of plugs have you tried changing them out?

[Polycraft]

Interesting, I didn’t know that. Post #2 still holds, If it was me I’d still check the coils with a resistance test, cheaper than replacing what could be a good coil(s). Your issues may not be coil(s). Can’t speak for the plug tester you refer to in post #1, never used one. Speaking of plugs have you tried changing them out?

The plugs were changed with the last service with no improvement. I have tried some 'mechanic in a bottle' to clean the carburettor, but haven't taken it out on the water since. It gets good reviews and doing a full strip down and clean or rebuild is a bit beyond my abilities. A resistance test seems a bit complicated and I would need to know what the resistance should be. A spark plug tester is very simple to use.

[Murray]

Get yourself a genuine Suzuki service manual, not from North America perhaps Australia? It will have the procedure for coil checks and carburetor rebuild directions. With the service manual you will get a better understanding of whats involved and you can then decide if the task is above your capabilities. You can buy a spark plug tester but if the plugs check out okay then what? The genuine Suzuki service manuals are laid out with lots of detail plus what I really like is Suzuki explains what the component does and how it interacts with the rest of the system(s). IMHO your at the troubleshooting stage which is where a service manual would be so helpful, it will walk you through the testing procedures and the values you should be getting. Your other option is to take it to a Suzuki dealer. Your last post you mentioned a resistance test is a bit complicated, it’s not, my service manual tells me which probe(positive and negative) to attach to the wire by colour and gives the ohms that I should be reading. Back to your issue, you are a bit light on details. Your running it hard then stalls when shifting into neutral or it stalls after being stopped then restarted and shifting into forward? What the fuel primer bulb like soft, hard? Any details you can provide will help with troubleshooting.

[Polycraft]

It stalls after a long run then trying to start it again after resting for a while (ie putting in gear). The revs drop when you do this so this is often when problems show up. That's why I suspected heat sink/ vapour lock. The spark plug tester will identify if the proper electrical charge is getting to the spark plug, so will show up a faulty coil. I don't think you can safely rebuild a carby from reading a manual and with no experience. Resistance tests can be done from instructions no doubt - but that is on the basis that I can get hold of a service manual and it actually describes this in detail. Remember I will be doing this on the water - it would be a lot easier to hook up the spark plus tester.

Yes I could take it to a dealer but they will probably have to run it on the water for an hour or so to reproduce the problem and have good troubleshooting skills (at lot of them don't).

[Murray]

Try the spark plug tester, you’ve got nothing to lose. I spent about 30 minutes looking for a service manual for your engine on Google and only found one other person looking for a DT 30 2004. All the DT 30 manuals I found stop at 1997, likely a North American thing. If your still in Australia I’d stop into a Suzuki dealer and inquire about your engine and a service manual. Perhaps other forum members that have more knowledge will chime in with suggestions. Good luck.

[Solarman]

To me, my input, this sounds more like a problem with fuel. Either a fuel pump is getting weak, or maybe a blockage in one of the small passages/jets/mis-adjustment of low-speed idle mixture screw(s). If you have multiple carbs all idle mixture screws should be set identically, plugs can tell a story by viewing them.

Also, there's is a possibility that the gear counting coil, or a TPS (throttle positon sensor) could be changing thier resistance after they get warm from running. Once they cool back down they go back to what resistance they are supposed to be.

The only way to know that, is once well warmed up, and acting up, check thier respective resistance according to the proper service manual for your motor.

Good luck, post back on what you find out.