1800 SR3 4.3L RPMS too high

[jfleece03]

My boat has been hitting RPMs over 5000 while going at speeds between 20-30 MPH and I don't know why. My RPM meter and speedometer have been malfunctioning for about 3 weeks now on and off and the speedometer finally just stopped working. I'm going to change the fuses on Tuesday when I take it out again but I was wondering, if the RPM gauge is working fine, what would cause the RPMs to shoot that high at such low speeds? I'm thinking about taking it in to the dealer to have it looked at but would rather try to fix it myself before doing that.

[CountryME]

Last week while running my 1900 SR 4.3 the tach started reading about 1000 RPM higher than it should. I went under the dash, disconnected the tach, cleaned up the contact and reconnected it...all systems normal. You may want to try that before taking it to the dealer.

-JP

[vffb507]

Could the prop be spinning on the hub?? The speedo is run by water pressure - look for a plugged line or intake on the front of the lower drive...

[shrew]

I wouldn't rely on the speedo for accuracy. Instead I'd be using the COG setting on a GPS which should be more accurate. The speedo is actuated by water pressure, so there is more than likely a blockage causing the speedo issue. I'd get the actual speeds confirmed first before chasing the RPM issue. However, you should still never be exceeding the max. RPM range of the engine. If this never happened before then you may be dealing with a spun prop hub. If it always execeede the max. rpm range then you might simply be underpropped. This is popular with skiers who are trying to get fast hole shots and have no intention of running at higher top end speeds.