Run Away 1984 Suzuki DT50!!!!!!!!!!!!!!!

[cubfan82]

I have a 1984 suzuki dt 50 the boat sat up for like 4 years before i bought it from my uncle and he was having the same trouble. 2 repair shops looked at the motor and couldn't figure out what was wrong. What its doing is... it will start fine and idle fine when I put it in gear and give it a little gas it wraps up to full throttle and will not return to normal idle, the key will not shut it down nor the emergancy switch. the only way i got it to stop was pulling the fuel lines and let it run out of gas. After it did that to me one time i decided to try my luck with a suzuki dealer, with no luck they told me that it was the carbs needed to be rebuilt and the kill swith was bad, quoted me like $1400.00 for the repairs. that sounded a little steap to rebuild 2 carbs. I decided that if thats all it was i could do it myself. I took apart the carbs to find that thay just needed to be cleaned really well. while i had the carbs off i went ahead and replaced all the gaskits back to the crank case. i guess my question is if the carbs, throttle linkage, fuel pump and gaskets are all clean and or new and working properly, what could i be? Keep in mind that iI just put the gaskets on tonight so I haven't got a chance to try it yet. I replaced the gasket at the advice of a different shop. that guy seemed to think I had an air leak at the crank case . would that make it run away and not shut down?

3 Shops, 5 mechanics, no real answers except the one guy that told me to come get my boat out of his shop and dont ever bring another suzuki back in there. So far all I've been doing is paying diagnostic fees and cant get any help.

hope someone out there has the answer

 

[JB]

Re: Run Away 1984 Suzuki DT50!!!!!!!!!!!!!!!

Howdy, cubfan.

Welcome to iboats.

You are getting thermal runaway. I never saw an outboard do that when under load.

Are you sure that it is in gear? Does the prop turn? Do the carb throttle plates open up or do they stay in the idle position? Does it happen every time or only sometime?

In a typical thermal runaway situation the engine gets revved with no load on it and switches to what I call "glo plug" operation, in which it needs no spark. If there is a lot of carbon in the combustion chamber it is more likely to runaway.

Runaway is very dangerous. Engines have been known to explode.

I am baffled that 5 wrenches, presumably qualified on Suzis, kept focusing on the carbs. I think the cause is mechanical, not fuel system related.

Let us know about the above questions. We have more expertise in outboards and more experience among us all than anywhere else on the planet. We can get it fixed.

 

[Silvertip]

Re: Run Away 1984 Suzuki DT50!!!!!!!!!!!!!!!

make sure the spark advance mechanism is tracking with throttle opening and not just flopping to full advance as the throttle begins to open. With the engine at idle, try spraying WD 40 at gasket surfaces, the seam where the two halves of the block meet, and perhaps up under the flywheel. No need to "saturate" the area. This checks for air leaks. The engine will pick up if there is a leak. You might remove the plugs and roll the engine by hand to check for excessive carbon build-up. Use SeaFoam to do a decarb operation if necessary.

 

[cubfan82]

Re: Run Away 1984 Suzuki DT50!!!!!!!!!!!!!!!

JB and Silvertip
It only happened to me once. and it happend so quick I didnt really notice the trottle plates position. but i do know that it was in gear and throttled up when i came back to the nutral position on the remote is when it started idle up higher and higher and then wouldnt shut off. thats when I pulled the fuel lines and waited for it to shut down and called a mechanic to see when i could drop it off.
I bought a repair manual online just to try to understand a little better the settings for the carbs and timing. I'm not a boat machanic and there have been so many hands in this thing that its hard to say what has been turned and tweeked. It hasn't been started since the last time it did that but since then The carbs have been cleaned, so did the fuel pump, new gaskets at the crank case and the reed valve plate, new spark plugs, and fuel filter. Im going to check for carbon build up through the spark plug holes, or is there a better way? If there is build up how do i clean it? I'm going to install a fuel shut off valve just in case and try to start it again.
Wish Me Luck I'll let yall know how it goes
thanks for the suggestions.

 

[JB]

Re: Run Away 1984 Suzuki DT50!!!!!!!!!!!!!!!

Sounds like Silvertip is on the right track, cubfan.

This is a likely scenario: When you shifted to Neutral the ignition stator stuck and failed to return to retarded position. Once it was in neutral it had no load, the power came on and thermal runaway resulted.

The fuel cutoff is an excellent idea.

Before you start her up again, check (or have a Certified Suzuki wrench check) that both the throttle linkage and the ignition stator move freely in response to your remote control. Then do a decarb treatment as described in the Engine FAQs.

Good luck.

 

[clanton]

Re: Run Away 1984 Suzuki DT50!!!!!!!!!!!!!!!

You in Panama City?

 

[cubfan82]

Re: Run Away 1984 Suzuki DT50!!!!!!!!!!!!!!!

Clanton
No Sir I'm in central Mississippi.

JB
That only Certified Suzuki shop near me is the one I took it to the First time. I dont really trust them to do it right and it took them 4 months to get to my boat and then another month to return one of my four calls. I dont have alot of faith in that shop Is there anything I can do myself to check the igniton stator and the linkage.

 

[JB]

Re: Run Away 1984 Suzuki DT50!!!!!!!!!!!!!!!

Yes, you can, cubfan. You need to get a copy of the factory Service Manual, which will show you how it should be connected and how to make adjustments.

Best of luck, and let us know what you find that the $95/hour "experts" couldn't.

 

[clanton]

Re: Run Away 1984 Suzuki DT50!!!!!!!!!!!!!!!

I ask because, I talked to a guy in Panama city that had same problem, he never called backed. I don`t know what the outcome was. I may be in Milton, Florida next 2 weeks, but still to far to drive. You want to get on the boat, remove the air silener from the carbs and call me cell phone I will guide you thru a few checks. PM for phone.