300 HPDI won't idle

[perryk123]

Runs kinda rough on the garden hose in gear at idle. Will accelerate to WOT and act ok, but when you bring it back to idle, it just dies. In the water it wont idle at all, had to rev it up to get it in gear and it will run wide open, but as you slow down close to and idle, she dies and will not restart for a few hrs.

drained fuel, replaced 10 mic filter

opened and cleaned vst (was very clean inside), replaced filter, fuel lines, and diaphragm pumps, check psi on vst all good 50 psi.

tried running on 5gal shop fuel tank same problem

YDS not showing anything unusual

cleaned air intake found some dirt and gunk stuck in there

replaced battery just to be sure it was not a voltage issue

compression is 120 psi on all cyl

checked spark with an in line spark tester, and all cyl are firing

was wondering if its a coil issue, but wouldn't that make it act up in higher rpms rather than idle range???

vz300 tlrc 2004 model on a Skeeter bass boat.

any help would be greatly appreciated.

We dont have a Yamaha dealer that really knows them around here, just part changers

[99yam40]

A good yamaha dealer should have the software and equipment to hook up and check it out, that is the only way to see what is going on

[Inducted]

You need to follow the instructions in your service for setting your TPS. It can be done using a volt meter but you do need the step by step instructions. Good luck!!!

[perryk123]

I have YDS 3.3 and everything appears normal. TPS, volts, Fuel Press, timing etc.

Wonder if its a weak/faulty coil, or maybe a clogged injector as it only has 40 Hrs and is a 2004 model. But don't know where to start

[99yam40]

You might try posting what all the reading are from YDS to see if someone can help see if something is out of spec.

Sure wish Rodbolt17 was still posting here, but maybe someone else that knows these motors and computer will drop in and help.

I would be worried about the low hours (non use) maybe filters and screens plugging up, fuel going bad, etc.
Sure won't want to eat pistons from running too lean.

[Inducted]

Even though you have an in spec TPS on yds if you have an idle issue double check all your throttle valves. OK throttle valves and tps are ok. Then check fuel pressure when problem occurs. If you have yds then monitor HIGH PRESSURE fuel readings on YDS. If the pressure drops below 798 at any rpm then you are probably not getting enough fuel to your high pressure system. clogged filter??? Using yds you can do a STATIC test for testing each injector. If you get a goofy reading between injectors then maybe one has an issue. Good luck!!!

[perryk123]

Thanks INDUCTED,

will try the static test agin and c if any variation. I think the H/P fuel reading was in the 600's and the L/P was right at 50psi that I checked with a manual gauge.

[mrpontoon]

dont know if there are the same as a 200 hpdi,but i had to do a sync & link to get a idle

[boats.net]

Need to sync throttle plates and readjust idle stop screw so the TPS reads 0.58-0.62. Make sure it has good spark plugs, only idles on four cylinders so spark plugs have to be good.

[gearhead74]

Sounds trivial but you may want to try a new set of spark plugs, they may be slightly fouled.