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DT75 Stalling on Idle after throttle back

D

dcook

New member
"Hi all,

As posted previou

"Hi all,

As posted previously I have an DT75 1995 model on a 4.3mtr boat. I took it out for the first time twice last weekend and the motor starts under choke and then runs no problem but once running it runs rough at idle until about mid-throttle when it runs better. Didn't get the chance to open it right up due rough water but ran it for a while at 1/2 to 2/3 throttle to see if that would clear plugs - the plugs look fine BTW. It also stalls when pulled from drive back into neutral, and will run fine with a little fast idle but that locks the controls from going into drive ! There is a mixture screw accessed through the front airbox - It sounded (and smelled) rich to me so as an experiment I tried leaning it out 1/2 turn and that made it worse, richened it back to original, then richened about 1/4 turn and it made little difference. I think I need to tune it up but don't want to buy a full manual just yet - not sure I want to keep the boat as it may not be fully suitable for my needs having tried it in open water on the weekend and found it a little hairy in more than about 1mtr of swell. Does anyone have an electronic copy of how to tune up a DT75 please or any advice please ?

Many Thanks

Cheers DC"
 
"HI there had the same problem

"HI there had the same problem. Time for a full carbie removal, clean and service. Petrol leaves a varnish when it evaporates and that can clog the jets after a while. Any small boat can be hairy in a 1m swell in unsure hands."
 
yep rebuild the carbs and fuel

yep rebuild the carbs and fuel pumps
replace all filters and run a fuel stabilizer
 
"Hi,

Actually I have one m

"Hi,

Actually I have one more thing to add to this before I start pulling carbs apart. Last night I checked the upper, middle and lower cylinder idle screws, which are accessed through holes in the front of the airbox. The top one was 1.5 turns open, (sort of what I expected) the middle one was 1 7/8ths open (ballpark, less than 1/2 a turn from the top one) and yet the lower one was less than 3/4 of a turn open - a huge difference to the other two. I used to have an old Evinrude V4 years' ago and also later a Blueband Mercury (both early 70's model engines) - and I was sure that the mixture screws were not usually more than about 3/4 of a turn difference between the cylinders, give or take a bit - but the lowest cylinder on this Suzuki was way different to the others. Also the further the screws are screwed in, the richer the mixture of that cylinder therefore that cylinder should be super rich - and I believe it is exhibiting signs of rich running - it certainly smells rich !

Also of note is the fact that with all the screws screwed all the way into the stop, none of the screw heads line up at all (not sure they should anyway, this would depend by chance as to what position the screw was in when the thread was cut) - so counting how far out they go must be taken from the fullstop position at whatever position the screw head happens to be pointing in fullstop - yet all the screw heads as set up on this motor were all exactly in line - too coincidental. I suspect a previous owner has simply lined the screw heads up in an attempt to make it idle better.

So, can anyone tell me what would be a "Normal" range for the mixture screw setting on a Suzuki Carb ? and should all 3 be somewhere within ballpark of each other ? Is the lowest one being so far different from the other two, normal ?

Thanks

Cheers DC"
 
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