Running Smooth But Requiring More RPM's

[Blue Ski]

I have a 95 Ski Nautique with a carbureted engine that is running smooth, has plenty of hole power, the prop looks fine, but to get to skiing speeds is running at record high RPMs. Normally I can ski at 34 mph with 3750 to 3800 rpm. To go 34 without a skier the engine is cranking at 4200 rpm. The story is same at cruising speed too. 3000 rpm usually is about 28 mph, now only 25. The tach is fine because the engine idle is dead on normal. Then engine has not been overheating, staying right at 160 degrees.

The problem happened before when I was burning some Speedway 89 octane but cleared up when I used 93 octane Shell fuel and opened up the engine for a few minutes. I thought it may have been the fuel but now it is happening again and I have not been back to Speedway. Does anyone have thoughts about this problem or have you seen it before? I just winterized this weekend so this will be a 'haul the boat to the dealer in the spring problem.' Thanks for the input.

[Rick]

Transmissiom Slip. How does the tranny fluid look? When was the last time it was changed?

[skinautique]

when is the last time the fuel filter was changed (I don't think this is the direct issue but it is one that should be addressed)

[Blue Ski]

The tranny fluid was changed at the beginning of the year (done every year) and I think the fluid is good. When I winterized yesterday I did not pay much attention to the fluid and I add a quart to protect against condensation through the winter so checking it now will not do much good. In the spring I get all of the fluid out and then go back to the right level. The tranny goes in and out of gear smoothly, would I hear or notice anything special if it was slipping? This seems like a very logical cause of the problem.

The fuel filter was changed in the spring too, same every year. New plugs, wires, cap, and rotor this year too.

Thanks.

[skinautique]

Did the problem happen before you changed the plugs, wires, cap and rotor?

[Blue Ski]

The problem did not start until September. The plugs, wires, etc. were all done in April. The engine has been purring like a kitten.

The label of data on the engine gives a max rpm's of 4400, but it quickly hit 5000 yesterday (did not overheat) to get to just over 40 mph. I brought it back down pretty quickly.

[skinautique]

sorry for asking so many questions but because I don't have the boat in front of me, it is the only way I can do it. What size prop is on the boat? I would definately rule out the transmission slipping. I would think that nms1991 or swcc-parts man could help out on this one. I think it is over my head.

[Mikeski]

Blue Sky,

I have a 95 ski nautique like you but I have a perfect pass on mine. One big benefit of the perfect pass is that it is a good reality check when the tach starts going wacko. The tachs in my boat is notorious for jumping between different 4/6/8 cylinder modes. At an idle there is not much difference in reading when it goes into 6 cylinder mode. I actually ignore it half of the time and rely on the perfect pass digital tach. My guess is that your tach is jumping between 8 and 6 cylinder modes. It's an easy fix. Pop the dash cover and move the selector knob back and forth a couple times, make sure it ends up on 8 cylinders. I seriously doubt that your engine actually went to 5000rpm with all of the prop blades intact.

Mike

[Blue Ski]

Mikeski,
Thanks alot for the tip, I did not know the tach had the different modes. I will check that this week and post the result. The engine was cranking, but 5000 does seem out of whack.

[nms1991]

Blueski do you have the PROTEC ignition system still or did you have it converted to a distributor? The only way to properly check your tach is to use a shop tach, by the way te3leflex gauges are not all that great of a gauge. I have replaced a few of the teleflex gauges before due to being inaccurate. If you still have the PROTEC ignition system it has a rev limiter built in at 5250 rpm, if you went out and ran it at wide open and it was running above 5250 rpm you would notice the rev limiter kicking in. I highly think it is more in your tach due to your description.

[Blue Ski]

I do not have the ProTec system, just the old school cap and rotor. I did not let the engine get over 5000 rpm according to the tach. Hopefully the tach is still good given that it is still dead on normal at idle.

Thanks

[Blue Ski]

The tach was firmly planted on the 8 cyl. setting. On to other possibilities, not to say the tach is reading right.

[nms1991]

Blue Ski did the boat get converted to the "old" school cap and rotor system or do you have a 96 ski when PCM dropped the PROTEC system? But if the trans is not slipping and the prop is not cavitating then the tach more than likely is reading wrong but check all your connections from the engine all the way to the tach to keep from buying an expensive tach to replace the original one.