Upgrading my prop

[Frose]

I just purchased a used 1998 Malibu response LX. So far I really love the boat. I’m trying to find out what the red line would be for the motor. I’ve been nervous so far to let it rev over 5000 RPM. I was considering putting a four blade prop on it with the same diameter and pitch since it’s more than willing to rev over 5000. I thought maybe that would bring down the RPMs while also giving me more takeoff power. Thoughts?

[UWSkier]

Which engine?  Carbed or injected?

[Frose]

I think it’s the Monsoon 2. It’s multi port fuel injected. 

[UWSkier]

Then you're fine going above 5000.  5200 is max RPM for that engine.  4600-5200 is the desired operating range per the Indmar specs.

What prop is on it now?  I run an Acme 515 on my Monsoon 2 in the same hull as yours and hit 5050 RPM by myself and 4750-4850 with a passenger, 1650' elevation.

Edited August 26, 2020 by UWSkier

[Woodski]

Operating range for that engine is as noted in previous post, 4600-5200 RPM.  In reality, since the engine is a GM small block, you can spin it to 6000 without damaging anything although not recommended or any reason to do so.  The hull drag will limit the engine speed.  My guess if you are running the original prop, it is a stainless steel CVP 13 x 13 three blade as that was standard issue in that era.  Prop specs and brand should be stamped on the hub.  Current prop recommendation and standard issue would be a Acme 515 if you are steering towards slalom and barefoot, if you plan to run the boat for slower speed sports, many use the Acme 525.  Would it be a correct assumption that you will use boat in Michigan thus 600'-1500' elevation?  If going to higher elevations, the 525 would be the better option.

Lots of good info here and a prop selection calculator:  https://acmemarine.com/