VP 5.7 WOT RPM question. Is 4100 RPM low?

[MalibuMike]

I've read that the WOT is anywhere from 4200 up to 5000. I have a 2007 5.7 Gi with fuel injection and trying to figure out what is normal. I have a VP duo prop but don't know the pitch. I'm getting 4100 rpm at full throttle on a Parker 2520 with 80 gallons of fuel on board.

 

[Scott06]

Your should be min 4600-5000, i think so e of the Merc mpis go to 5200 on the same block.
bottom line prop it such that you get 4900-5100 light load and the performance will be good.
i would verify your tach is accurate and in good working order. what is yiur speed at 4100 rpm

 

[Lou C]

Agreed verify the tach and try to get it close to 5,000 light load, that will reduce engine strain over time

 

[QBhoy]

Your should be min 4600-5000, i think so e of the Merc mpis go to 5200 on the same block.
bottom line prop it such that you get 4900-5100 light load and the performance will be good.
i would verify your tach is accurate and in good working order. what is yiur speed at 4100 rpm

I think there are some slight differences between a Gi and a merc mpi occasionally. The gxi is usually the direct comparison mostly. But if it is comparable, it’s either 4600-5000/5100/5200 I think on the mercs, depending on set up.
Otherwise it’s likely lower an around 4800 max like the efi and gli models. But there are a few variants to confuse us all with VP…as always.

Anyway. I’d perhaps ask about if the boat is being trimmed properly with the drive ? Or are the trim tabs being left down at wot perhaps. Both of these can lose hundreds of rpms off wot, as we will all know.

 

[mtboatin]

My '94 7.4 GI sticker says 4200-4600. It may not matter but mines a DP. I know it's not the same beat though.

Not sure of you boat engine's maintenance, but make sure it's 100% before playing with props. My boat sat almost four years prior to purchase and between 98 gallons of old fuel and secondaries stuck shut I started out at 2800 rpms warm. After additives and fresh fuel, closer to 3200. Now close to 4200. This spring I'll do plugs and check timing. In my case at over 5000 lbs and 27' I'll be happy with 4500 if I can see it. Still probably won't brake 40 mph.

If you want a step by step of my situation you can see it at "Top Speed Issues"

Top Speed Issues

Hello all. I recently purchased a 1994 Cobalt 272. This boat is equipped with a 7.4 GL PMDM and B2 props. Slowly going through things. Boat has sat close to three plus years with a full 98 gallon tank. Fuel smells fine but you know....three year old fuel. Added multiple high end fuel...

forums.iboats.com

 

[bruceb58]

Your owners manual will state this. If you don't have one you can download one for free based on your serial/model number.

Here is a page from one I have