1986 DT200 Trouble, Running out of ideas....

[Beantown]

Hello everyone, i bought a boat that came with this motor, and have been restoring the boat, and have really never got this motor to run right. It always starts right up, and idles fine, engage the engine and as you get on the throttle, it starts to run rough at 1300 rpms, and if you continue to give more throttle, it almost always stalls out, and will fire back up and cruise around slow until you try to get on it again, and sputters and starts to die, but if I play with the throttle off and back on some times the motor will smooth out and take off and run until i get to my destination. This happens every time i try to make a run, and I have to start and stall until it runs, which can take twenty, or more tries, it I have removed the fuel cell, and washed it out with K100. and replaced all of the fuel lines and vent fittings, hoses and clamps all new, had the carburetors, and both fuel pumps rebuilt by Suzuki mechanic who was very hesitant to work on it, after four other places said no, the big dealer here said they wont work on any motor older than 2014. I am super frustrated with this motor, is there possibly an electronic problem I should be looking for? does the CDI unit control anything with the fuel delivery? What am i missing, I have always assumed it was a fuel issue, but now I am super confused, any input would be greatly appreciated.

[briscoe]

Whew, I was thinking fuel issue too. Have you looked at the plugs. I set my plugs with a gap too wide and it was very cold natured. After I adjusted them correctly it acted much better.

[Solarman]

I'm not sure what you are talking about "fuel cell"? Your problem could be related to the TPS (throttle position sensor), or you might still have a fuel related problem, if carbs weren't cleaned properly? It's difficult to diagnose from the description you have given us. Do all the gauges work? Are there any diagnostic codes flashing? Does the motor run smoothly at idle?

You are our eyes and ears, the better you can explain, the more we can help. Do you have the Suzuki service manual for this motor

Good luck, post back on what you have.

[briscoe]

Solar man, I think he's talking about fuel tank, as fuel cell

[Beantown]

Hi Solarman, yes, i was talking about the fuel tank, all of the gauges work, no alarms or trouble codes, and it runs smooth at idle, and runs smooth up to around 1300, to 1500 rpms, before it starts to sputter out, and yes i have the service manual for this motor, I went back to the spark plugs, as Brisco suggested, and found that they were fouled, (brand new plugs a few weeks old) very wet and some carbon build up, and my gap was not correct, manual gives .035 to.039 range for a gap, in inches, so I installed 6 new plugs, and I set them at .035 and it seemed to run a little bit better, only ran it for a half hour approx., so I pulled the new plugs when I got home, and they seemed pretty wet to me, I know its running a little rich, so I cleaned the plugs and increased the gap to .039 in. and now I'm on my way out for another test run. I appreciate the help from everyone, I will report back how it runs today, yesterday was the best it has run for me, since that was really only the fourth time it has been in the water in at least four years, it jumped right up and was running at 56 mph, with a banged up prop, that needs to be tuned up, its bent and chewed up a little, but thats how i bought it, and i didn't want to sink any more money into this motor if I cant get it to be reliable first. I am hoping I'm on the right track now.

[SirIzzy]

Hi Beantown, I have a Mariner 90 HP that exhibited similar issues late last summer. Turned out to be a sticking anti-siphon valve that comes out of the tank. You may or may not have one. The way I tracked it down to the anti-siphon valve was when it did stall, the fuel bulb would be squished almost flat. I removed the anti-siphon valve and in my case solved the problem.

[racso65]

Beantown, I had kind of the same problems with an 86 dt150 i had , hope everything went good today. but if it continues, you should check the CDI and magneto coils (pg43) i went through the same nightmare until changed both of those.

[Beantown]

thanks so much everyone. sirizzy, I will check that anti siphon, I think mine is on the fuel pick up, I will be checking that next, and rasco65, I was wondering about that CDI and magneto coils, thats next on the list, thanks, so today I took the boat out to the lake, the motor ran night and day better today, still probably running a little rich, still has a slight hesitation at 1300 rpms, but it really gets up on plane in seconds and really flies, but now I notice my brand new tachometer, is running at 5300 rpms, at 3/4 throttle if I max the throttle, it will reach 6000 rpms. I tried my best to run the rest of my test run around 5000 rpms, shut the motor off and started back up again, went on five or six good 1/2 to 3/4 mile runs, boat was very dependable today, what a difference, but know I have a prop, issue.This motor came with this prop on it, which is a 3 x 14 - 1/2 x 20p, the manual lists 18p 20p 22p 24p 26p 28p. should I start with a 24p ? thanks again

[Moonlighter]

Most AS valves are connected direct to the tank pickup.

They are responsible for lots of fuel related problems. I would just get rid of it.

Mate had same issue with his Striper stalling at idle when dropped back to idle speed after a run. I undid the AS valve from the tank, took it to the workbench, and punched out the little ball, spring and seat from inside, so it was then just a straight thru barb, and re installed it on the tank. Used some gasket goo cement on the threads to ensure they sealed. Double hose clamps on the fuel hose. Problem solved.

Even if this isn’t your problem, it only takes a few minutes to do what I did, costs nothing but your time, and prevents likely problems down the track. No brainer really.