'06 DF90 power issue

[QSS_Ryan]

Hi Guys, I have a weird one for you all...

Early in January I took the boat out (It had been sitting for 2 weeks max without use), left the ramp and throttled up to 4500ish. Sat there for about 10 min, then all of a sudden the revs dropped back to just under 3000. The more I pushed the throttle, the more it struggled.

Anyway, puttered back to the ramp, trailered the boat and took it to the mechanic. Found that there was a water contamination in the fuel, and did my major 450 hour service while at it. The water had filled up my water separator and then allowed water through to the engine by the looks of it.

After the service and discovery of water, I geared up with a freshly cleaned water separator filter, and the boat lasted all of 2 mins before having the exact same issue- revs around 2800, the more I push the more it struggles and sputters.

I spent the next couple of weeks running the boat regularly (from a jerry can) to push through water that is still kicking around the engine- draining the vapour separator after every couple of hour stint.

Anyway, it has seemed to get past the original issue now, am able to run at full revs again....

I took the boat out early this week- had only one hiccup on the way to my spot (about 30min cruise across a bay), but I just dropped it into neutral, turned off the engine and turned it back on again- ran perfectly the whole rest of the way. On the way back it lasted around 15-18 min before it dropped back again. this time, when I turned it off and back on again it was able to rev to full revs, but after 2-3 min the same thing happened again. And the same result every time I dropped back to neutral, switched off and on again, and powered up. It will power up fine, run for a couple mins, then drop off again. It did this 3-4 times, then was fine for the rest of the trip back (about 10 min by this stage).

Took it out again to the same spot two days after the above incident. Ran perfectly all the way there, not a hiccup at all. On the way back, almost in the exact same spot, the same issue again. This time it continued to happen and happen and happen despite my restart technique that had worked in the past!

So Now I'm thinking it's not as easy as a fuel contamination, the vapour separator has had no water in it the last few times I've drained.

Anyone have any ideas? I'm stumped

Cheers,
Ryan

[boats.net]

Probably need to remove and clean Vapor Separator tank.

[QSS_Ryan]

Thanks mate, I took the Vapor Separator out today and gave it a good clean with carbie cleaner. There was a lot of scaly shit on the sides, but no signs of rust or anything. Got it all back in, will let you know how the boat goes tomorrow!

[pniksnut]

also check the high presure pump inside the seperator if it works ok . there is also a very small filter. inside the injectors are also very small and dense filter which may be the couse of your problem

[QSS_Ryan]

Well the vst clean solved the problem, at least for this latest trip. Ran perfectly!

Yeah the little high pressure filter was pretty gunked up.

I also added fuel stabilizer to the 100L of fuel I put in for the injectors etc

Cheers guys, hopefully that's done the Trick!

[spitzerone]

I've had the same issue with both Suzuki and Mercury outboards. If you are in the US, my guess is that you are running 87 octane gas with ethanol in it. This is murder on outboards if they still up for awhile. If you are going to let your boat sit up (like during the winter) use Sea Foam in the tank as part of the winterization process. It will alleviate this from happening. If you fish through the winter as I do, you won't have the problem. The ethenol gas makes moisture in the tank. I learned my lesson the hard way.

[Harper]

If you live in an area that has cold winters, and you have to store the boat for the winter months, the best thing you can do, especially if you use gasohol, is to drain the fuel tank, and run the engine to run the entire fuel system dry. The next best thing would be to fill the tank completely, to reduce the airspace in the tank to a minimum and help prevent condensation in the tank. These measures are especially important in cold damp regions, such as the Pacific NW in the US. Ethanol has an affinity for water, and will absorb it from the atmosphere. As long as it isn't too heavily loaded with water, the ethanol will hold that water in suspension, and it will have little effect on the motor. But once the ethanol reaches its saturation point, the water will start to separate from the ethanol, and settle to the bottom of the tank. This is what is known as phase separation. Once you encounter phase separation, as QSS_Ryan obviously did, you will experience problems. And as QSS_Ryan found out, once this happens, you must clean the entire fuel system. Proper cleaning involves draining the tank, the fuel lines, the VST, and the fuel rail, and cleaning or replacing the fuel filters. If you are lucky, you will not have to replace the injectors, but I have seen instances where that had to be done. In any case, take steps to prevent water absorption. Correcting the problem can get very expensive.