91 ski nautique engine trouble

[megg]

i took my boat out last night and timed it. it was dead on to begin with. the knock sensor works. im thinking the knock sensor is what everyone is calling limp mode. carb is working properly, choke is opened and primaries and secondaries are opening all the way. the only thing i can think of is i have an exhaust problem. does anyone know if the muffler can cause low end loss of power and high end loss of rpm? Im thinking i may have a failed muffler. the exhaust pipe is clean from the back of the boat. i shined a light in there and it is not clogged. i have a single exhaust exit of 4 inch pipe. the only thing i can think of is this may cause a breathing problem. only other thing a can think of is my transmission is slipping......though the oil is full, it is not making any noises and ive never had a problem with it before. i beleive its highly unlikely the transmission is failed. has any one had to replace a muffler? please help if you can. thanks.

[GZA]

Hi Megg

If you have a bit more of a look through the older posts you'll find out about the limp mode. It will come into play if the motor is over temp'd or has low oil pressure (I think with this one - can't remember off the top of my head). There's a red light on the top of the dash which will illuminate if this system is working. You can bypass it by diconnecting temp sender and pressure sender, and see how the boat runs then. Could be a faulty sender.

If not then it could possibly also be a coil pack. We had a problem similar where the boat would run fine under no load but not pull above 3k and bog down. New coil pack fixed it but they are hard to find.
Rob

[M3Fan]

ICBW but doesn't Pro-Tec adjust the timing automatically? I don't know that you can adjust the timing on a Pro-tec system as there is no distributor.

[darrel409]

It may be a fuel starvation issue. Check all your fuel lines and clamps from tank to carb, make sure there are no air leaks or kinks. Do you have a fuel/water seperator? recently changed? Dirty fuel filter? I dont think your boat should tach to 6000 rpm, your max is probably about 4400. Your oil pressure and temps sound fine although 190 is on the high side for temps. And I agree w/ M3fan Pro tech adjusts timing automatically.
Where is DavidF when you need him?

[skijones]

Check the pickup tube in the fuel tank. There is a cone shaped screen that can partially clog and cause similar symptoms.

[efox]

The protec is the precursor to an onboard computer. Some relay is telling the ignition system that the engine is out of spec for whatever it measures. The temp sender may be an issue or the oil pressure sender. It could be lots of things. It could also be that one of the coil packs is beginning to go on you. I hope it is not that as they are very expensive and hard to find. I had a couple of plug wires crossed and it acted a bit like you say your's is acting. I would also check the ground near the driver front side of the block. My ground was a bit loose. I need to fix one behind the dash too...just haven't had the time. They are good boats and the Pro Tec is a good system...just really quirky. Oh, I agree...your boat does have a limp mode, but I don't think you are in it.

[DavidF]

Limp mode due to low oil pressure is activated by a switch that is seperate from the gauge sending unit. Disconnecting the switch at either the oil pressure or engine temp switch will effectively kill limp mode.

Your engine also has "cruise" mode which automatically advances the timing when the throttle has not been moved for 30 seconds. I suppose you could be stuck in "cruise" mode. To deactivate "cruise" mode, disconnect the knock sensor wire from the knock sensor which is located in one of the block drain holes (cannot remember which side).

It very well could be other Protec related problems.