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Old 25-02-2016, 12:50   #1
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DT85 outboard intermittant acceleration

Hi All,

I have a problem with a DT85 Suzuki outboard.

When i FULLY open the throttle the boat revs at around 1500-2000 rpm and goes no faster, then after a while it will pickup speed and seems to run fine at around 4000-4500 rpm.

Sometimes when backing off the throttle completely after its been running fine, the problem starts all over again, other times i can accelerate off the bat and its fine.

From what i have read on forums it seems to point to a fuel/carb problem.

But i am not a mechanic and not sure where to start?

Any advice would be appreciated.

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Old 25-02-2016, 13:13   #2
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Re: DT85 outboard intermittant acceleration

Learn as much as you can by watching it on youtube if you're planning on doing it yourself.
Suzuki are generous with free manuals online.
Not technically demanding but do read the manual, study the exploded drawings.
Take photos & make your own sketches as you work so the manual makes sense.
Lay parts in order - first off is laid furthest from you on your beautifully clean, otherwise empty bench. Reassembly then is easy, rebuild from nearest to furthest.
Anything you don't understand, stop & study until you do. Don't force anything &...

have a service kit ready before you start.

Or you could just try carb cleaner first if you want. Sometimes it works.

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Old 25-02-2016, 13:20   #3
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Re: DT85 outboard intermittant acceleration

First thing I'd try is a new set of spark plugs.
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Old 27-02-2016, 10:47   #4
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Re: DT85 outboard intermittant acceleration

Sounds like a carb issue to me, as well. But before getting into that, try running at low speed until it's warmed up, then crank in the throttle. If it lags, try squeezing the tank line bulb. If the revs pick up, slow down, pause, repeat. If it works 3-4 times, suspect is the fuel pump diaphragm (follow fuel line from hose connection to carb).
If the bulb makes no difference, problem could be either junk in fuel bowl or a sticky bowl float. First pull drain plug from bowl and drain fuel into a catch. Shallow white plastic, like a spray can cap, works well. While the drain is open, you can try spraying carb cleaner up through drain hole, give it a good long squirt to hopefully flush loose crap out. Reinstall plug, connect hose, squeeze bulb to refill bowl, try running again.
If problem persists, you'll probably have to pull the carb, open it up and check-clean as needed. Check the float level height - the manual should describe how, with a pic of proper level. The float engages the needle valve via a brass finger, and if the finger is at the wrong angle it will close the needle valve with too little fuel in the bowl. At higher revs the jet will suck air until the fuel level rises back up to meet to, resulting in engine speed slowing, speeding back up, slowing again.
It's a good thing to know how to get this done yourself.
Good luck!

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Old 27-02-2016, 11:10   #5
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Re: DT85 outboard intermittant acceleration

1) if it has a rubber mounted prop spline, you may need a new prop. Although this usually exhibits as high rpm with low speed.
2) I had a 15 hp outboard that had bad main bearing that did as you describe.
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard

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