RPM Question

[sonworshiper]

Hello all, This may be a stupid question.... but I don't have an engine manual for my 4.3 v6 mercruiser. What is a safe range of RPM's? The tach goes to 6k but no red line is indicated. I don't want to damage the engine by reving too high
Thanks in advance!

 

[texasrider]

I believe the recommended RPM range is between 4400-4800 at WOT (wide open throttle) during normal operating conditions. At least that's what I read when I was looking for a new prop.

 

[sonworshiper]

Thanks Texasrider, I appreciate the help

 

[comsnark]

That 4400-4800 RPM recommendation is W.O.T. . . you really CANNOT spin faster than that, unless you have props that are too small. If you can't get RPM to that range, then your prop is either too large, your bottom is fouled, or something else.

I believe if you browse the searay website, you will find a "prop selection chart" that should give you recommended max RPM.

In terms of normal operating. . . you really are shouldn't run over 4,000 RPM on an ongoing basis. This is from a wear-and-tear perspective, and a number of people recommend a 4,000 rpm day-to-day limit.

In general, you want to 'cruise' at just over the minimum RPM it takes you to stay on plane. For sport boats, this tends to be around 3,000 RPM. For heavier gas powered cruisers, this can be 3,400-3,600 rpm. (diesels are different). If you want to go fast and zip around at 3,600-3,800 rpm . . you should be ok.

 

[midway]

The best fuel economy and speed for cruising on my 185 Sport is about 3500.

 

[sonworshiper]

Thanks guys! I am going to have my tach checked. At wide open throttle it pegs at just past 6K. The prop is stock so I'm assuming the tach is off.

 

[tdappleman]

You can check out this link as well - might fix you as well.

http://clubsearay.com/forum/showthread.php?t=11727

 

[Hampton]

We have a very similar boat name in our area - "Sonworshipper." Very interesting story, and an excellent boat ('07 400Da).

 

[sonworshiper]

Thanks! I'll check out the tach switch and let you know what happens. I also noticed that the trim indicator is off. When the outdrive is all the way down it still indicates slightly up.......

 

[sslewis1]

Gary,

I have all the factory manuals, and I can confirm the 4400 - 4800 RPM WOT range for the 4.3 Merc.