2004 Mercruiser 4.3L Alpha Drive High RPM

[alukken]

I recently purchased a 2004 Bayliner BR 185 with the Mercruiser 4.3L 190 HP engine, and the stock propeller.

I took the boat out on the water last night, and when I opened it up to about 3/4 throttle, the tachometer hit 6000 RPM, at about 40 MPH. When I had the throttle wide open, the tachometer went past the 6000 RPM, and pegged out at what would have been 7000 or 7500. (Tachometer ends at 6000 RPM) The boat topped out at around 53 MPH, which is what I read online it should. The engine didn't sound as if it was really running at very high RPM, but I read online that this engine at WOT should be anywhere from 4400 to 4800 RPM.

Thoughts, do I have a bad tachometer, does it need to be calibrated, or is there something else going on?

Thanks,
Tony

 

[Haut Medoc]

Re: 2004 Mercruiser 4.3L Alpha Drive High RPM

Welcome to iboats.......
On the back of the tach there should be a selector for 4 cyl, 6 cyl & 8 cyl......
My guess is that it is not set to 6 cyl......​

 

[bhammer]

Re: 2004 Mercruiser 4.3L Alpha Drive High RPM

On top of that, make sure your Tach is accurate by using a know good tach to verify RPM. You can pick one of pretty cheap at wally world or your local auto store.

I have had / seen boat tachs that are way off. Early on, it cost me buying an incorrect size prop becasue I thought I was way under proped. Come to find out, my tack was about 150 under at 600RPM and about 500 at WOT.

 

[Bondo]

Re: 2004 Mercruiser 4.3L Alpha Drive High RPM

Thoughts, do I have a bad tachometer, does it need to be calibrated,

Ayuh,...... That would be My Guess..........