What(39)s the max RPM I should cruise Mercruiser 5.0LX

[Francorosso]

I have a 2001 2455 Bayliner Ciera with a Mercruiser 5.0LX. The RPM gauge goes up to 6000 with no red line. When I push the throttle all the way up the RPM is at 6000 (5500 with a full tank of gas), and I'm wondering is it ok if I run it wide open all the time? I understand about how much more gas you use at high RPM for very little increase in speed, but what I care about is whether this engine is good to run at 6000 RPM all day long without any worries. It has always made me nervous running an engine at full throttle for extended periods but perhaps that's what these are made for. I welcome all opinion and your experiences but I'm most interested in what the manufacturer recommends which I can't seem to find online.

Frank

[builderdude]

Don't run it there! WOT is used for testing purposes only.

[SprinterX]

"builderdude" post=813987 wrote:
Don't run it there! WOT is used for testing purposes only.

AGREED.

While not the same engine size or boat, I try and limit the RPM to about 75-80% of WOT. In my case when tested I reach 4,600 rpm on my carb'd 5.7's which equates to 3,600-3,700. This proves to be the sweet spot in my application for ride, performance and efficiency.

Hope that helps.

[builderdude]

I think most guys tend to run the rpm at the slowest speed at which the boat will plane or a touch above. The fellas that have fuel flow equipment will likely run the rpm at where they achieve the best fuel economy. My 2556 will plane around 2900 rpm (pending conditions) but I'm usually running around 3200-3400 rpm.

[Don77]

If you can run that engine up to 6000 RPM you are way under propped!!!

You need a prop that has a higher pitch! As in going from a 15 inch pitch to a 17 inch pitch!

Good luck and enjoy your boat but DO NOT run it at 6000 RPM! Run it at a much lower RPM! But you should change that prop!

Don

[desuch]

mine also
..........

[desuch]

I have contacted bayliner on this issue they have told me that 4600 rpm is max anymore you have the wrong prop.I run mine at 3200-3400 rpm using a 15.5 x 13 prop. that gives me 4100 rpm

5.7 liter mercury carbed. engine cobra drive

[TerryW]

After 10 years with mine, the "comfortable" cruise RPM is 3600 to 3800 depending on the amount of slime on the underside and the amount of wave action trying to reduce your plane. I use my 8120 computer to monitor GPS speed and fuel flow to get a really good understanding where the engine is at its most economic at cruise. I run a 4 blade aluminium prop which was a revelation when I installed it.

[Guest]

You are certainly over-revving your engine past 4800RPM, you should get a prop with at least 2" more aggressive pitch to get that under control and get better top end efficiency. For me best cruising RPM is between 3800 and 4000, I have 2004 Mercruiser 5.0 TKS (its a 305 cid double barrel carb with automatic enrichment for turn key start). I currently run 3 blade 16x16 aluminum prop and when lightly loaded I reach max RPM just barely where limiter kicks in near 4800 RPM. When heavy, I can only get about 4600 RPM, this means my prop is ideal for the weight of my boat.

On second thought, before you spend any money on props. Get a calibrated shop tachometer and actually measure your WOT RPM. I just can't believe 305 mercruiser would spin that fast without puking valves out in a hot mess. The in dash gauges can be inaccurate or faulty.

[Francorosso]

Great answer, how can I find the specs of my prop? Are they on it? And is there a website I can go to try and choose the right prop?

[Francorosso]

I'm curious myself now. I have a shop tach but the leads are short, I'll have to figure something out to read the rpm while cruising.

[Francorosso]

There's an RPM limiter on Mercruisers?

[Ruffryder]

Yes, but only on those newer MPIs & TB5

[Guest]

My 5.0 2bbl is rpm limited to 4800

[Ruffryder]

"Jakeallred" post=815851 wrote:
My 5.0 2bbl is rpm limited to 4800

If you have a TB V ignition system, yes the Rev-Limiter is set 50 RPM above the maximum engine RPM.