2005 DF200 rpm revving up- lost power

[dcnguyen63]

1st test run to start our 2012 season, my suz's rpm suddenly revving up every minute. It can rev from 2000+ rpm to about 4 or 5000 rpm while lost thrust power completely every time it happens. Port and Starboard engines behave the same. I have to shift them back to neutral then re-engage "F"orward to keep it moving again every minute or so. Seem happens less with rpm under 2000 though. This happen in 40 mile round trip in 2-4 ft sea. Back to calm water, have a mechanic plugged in his laptop to engines, ran thru all rpm range but cannot reproduce the problem. 10 days later, heading out to fish in 2-3 ft sea, made 50 miles trip no issue.. but next day trip, "rpm revving up" problem happens again in calm inlet water until we re at 1 mile out then they dissapear completely for the next 60 miles. Kind of wary and cannot plan any trip if our engines do that randomly.. Never had this issue since we bought the boat at 400 hrs.

[boats.net]

That is definately an unusual problem, I am uncertain to where you should start. Those motors are completely computerized and should show a code.

[dcnguyen63]

Our marina mechanic found we have bad high pressure fuel filters (70-80% restricted). Replaced them both (1st time & currently at 600 hrs). But we still not 100% sure they are the reason.. will have to wait until we can test run again.. how often we have to replace these filters?

[Harper]

.. how often we have to replace these filters?

Depends on the quality (and age) of the gas you're using.

[dcnguyen63]

maybe bad gas?? big mistake for use no stabil

we had full 220 gallons since Oct 2011 and used no stabil during the winter storage. Our 1st trip was on May 5,2012..since then I have refilled with 120 new gallons. gas from marina was ethanol free I guess.. as 200 boats were stored there filled the same gas. I need to verify this with the marina and may need to check the racors (replaced before we made our first trip)..

[Harper]

My guess would be that you've found the source of your problems. I would never assume that any gas is ethanol-free, unless specifically advertised as such. Even then, I'm inclined to test it for ethanol (I carry a little test kit with me). Most marinas sell the gasohol now. And if your ethanol-laced gas goes into phase separation, there's no filter in the world that will protect your engine. Water separators are for separating out water still in suspension (in the ethanol), not water that has separated out of suspension. If it were me, at this point I'd get rid of the present fuel and replace it with fresh fuel, only enough at one filling to get you through a month or so. It's unwise to put 200+ gallons of fuel in a boat if you use only 60 gallons a month, and doubly so if we're talking about gasoline "contaminated" by distilled corn juice. If you are talking about having the tank full for over-winter storage, then yes, it is a good idea to have the tanks full, but an even better idea to drain the tank. And if you leave it full, do use an additive to help stabilize the fuel. Because ethanol or no ethanol, it'll start going bad in a couple months. And if I read your initial post correctly, the boat was stored for close to 7 months.

[dcnguyen63]

Still having this spiking rpm's - NEED HELP !!

After spend another 400-$500 to replace all the fuel filters.. and boat has to sit for a month due to sea condition, we finally have a chance to take it out.
1st day, by the instracoastal way, I notice the port engine's rpm spike up 2-400 rpm and back to its normal rpm.. offshore in 1-2 feet sea, we ran the boat fine with this port engine little issue for 160 miles for 12 hours, running and idling. Second day, the sea is roughed up to 2-3 sea chopping due to thunderatorms.. the port engine act up immediately with rpm spikes to extra 4-800rpm constantly and the starboard engine behave the same with less occurance.. then for an hour, the port engine has its "temp" light on. I shut it down.. now running back with the starboard engine only and suddenly the oil light blinks constantly..

Back to the dock the same mechanic check everything out again saying he will put a mechancal bypass on the starboard to stop it;s blinkng light at the helm. For the spiking rmps, now he say he will check out crankshaft position sensors to see if it is malfunctioned.

Do you guy have any suggestion? Engine is at 590 hrs.. already spent $2K but the problem has not been clear..

I will post some video links while at sea with the issue?

[dcnguyen63]

with new props still has the issue

Trying to solve the jumping rpms (suspecting overrev or props blowout), bought a new pair of Quicksilver aluminum 4x15.5x16.. engines perform well wiith no hiscups in the ICW but when it hit the boiling inlets with 3-4ft waves mixxing up with outgoing tides.. the rpm start to jump from 4000 rpm to 5000 rpm.. Limping 1/2 day in 3-4ft sea.. Next day 2-3 ft.. we fare better with less "overrev" occurance, and then when it for "2 feet or less" sea, we are flying out to 30 miles offshore with no "over revving", going back on 2 feet following sea didn't seem to get the jumping rpms to occur.

so my guess are the old pair of props might get spun a little but with new out of the box props we still see the rpm revving up issue.. This points me toward ventilations. Either the exhaust gas escapes to the blades area or there some nick in the hull that cause the ventilation or the ventilation blades..

Any ideas..

[dcnguyen63]

eractic rpm revving up problem cleared

Took us 2 months, new props, all new fuel filters to suspect the corrosion has played its part on our wiring harness. After we replace the wiring harnesses, my engines are now silky smooth as before.. Been running two 8 hrs trips non-stop in choppy 2-4' and rpms are stable throughout the ranges. I think Suzuki has changed their wiring harness by moving the white wire fuse to the ignition end. 1 piece harness design with 1 connector in the engine and one at the iginition. We also have to get a new dual ignition switch to use the new wiring harnesses. Quite expensive repair this year but glad that we don't have to repower.

[djbuys]

Took us 2 months, new props, all new fuel filters to suspect the corrosion has played its part on our wiring harness. After we replace the wiring harnesses, my engines are now silky smooth as before.. Been running two 8 hrs trips non-stop in choppy 2-4' and rpms are stable throughout the ranges. I think Suzuki has changed their wiring harness by moving the white wire fuse to the ignition end. 1 piece harness design with 1 connector in the engine and one at the iginition. We also have to get a new dual ignition switch to use the new wiring harnesses. Quite expensive repair this year but glad that we don't have to repower.

Hi dcnguyen63, I have the exact same problem on a pair of 2011 model DF300s.
Also fine on flat water, overrevs when sea gets bigger.
Which part of the wiring harnasses did you replace or did you replace them all?
thanks!