High RPM

[markwarren66]

Hi - <br /><br />I have recently purchased a 2002 Wellcraft 190 with a 4.3 190hp Mercruiser I/O. The tach is reading in the 5500+ range at WOT with a normal load. The boat runs great, however. <br /><br />The boat came with a composite "Piranah" prop on it and an aluminum spare. I'm going to put the aluminum prop on and see if that makes a difference. <br /><br />My question is - since the WOT range for the Merc should be 4400-4800, if I'm indeed 1000 rpm over, shouldn't I notice something else? Don't engines have warning sounds if you're redlining? <br /><br />I don't have the owners manual yet - ordered and waiting for delivery. <br /><br />Could it be a bad tach? Or do you think the composite prop could be the source? The composite prop is a 4 blade 14x22. The aluminum prop is 3 blade 14x19. <br /><br />Thanks

 

[Haut Medoc]

Re: High RPM

Put the 14x19 on it & see what happens....<br />There is no over rev alarm that I am aware of....<br />I would not run it over the wot range except for a short test....<br />I would get a separate tester to verify the gauge....JK

 

[markwarren66]

Re: High RPM

Ok - I did some more investigation. I can see the back of the tach gauge, and there is a switch for 4, 6, 8 cyl engines. Right now, the switch appears to be set for a 4 cyl, while it should be set for 6. <br /><br />I moved the switch over one position, so hopefully that settles the issue. Won't know until Saturday, though.

 

[markwarren66]

Re: High RPM

OK - I took it on the water yesterday, and the boat wouldn't start. Dead battery. No big deal, replaced battery and rest of the day went fine.

The tach is now running low.....WOT at 3000 versus near 6000. Sooo, I think I moved the switch from a 4cy to the 8cyl, skipping the correct 6 cyl setting. I didn't have my long screwdriver on the boat to adjust on the water, so I'll have to wait until next time to confirm.

If WOT was near 6k on the 4 setting, and near 3k on the 8 setting, when it's corrected I should be hitting 4500 or so....that was with a real heavy load too. So, I think I'm ok.