My Mariah is a dog
 

Actually probably not but I've had some serious issues. Bought a 2001 24' Shabah a few years ago. Found out in the first season that I had been sold a boat with a cracked block. Replaced the engine in the second season (Volvo Penta with an Penta outdrive) and ran it the following season. My issue is that if I have more than two people on this boat it won't plane for anything. I literally have to put people on the bow to plane out. Thinking prop, and considered trim tabs (was told it can't be done because of the transom shape) but I need to narrow the possibilities. Also only running about 3800 RPM's at top speed which the installer said was correct but IDK...Seems like that's very conservative. Any ideas??? I'm getting frustrated!

Re: My Mariah is a dog
 

3800 WOT is way, way low!
Depending on motor , you need to be in the 4400-4800rpm range.
Sounds like your running too much prop. They are usually stamped on the side as to the size.
If you'll do a search for "smart tabs" you'll find lots of info on installing tabs on your boat.
Is she running good?

Re: My Mariah is a dog
 

As Larry noted, 3800 rpms at WOT is way too low. Depending on which 5.7 Volvo you have the WOT max is either 4800 or 5000. You can check that out here.

First thing i would do is to confirm what gear ratio you have and what prop is on the boat now.

Re: My Mariah is a dog
 

Thanks guys...You are confirming some of my suspicions. Just got her out of storage so I'll do some investigation of the finer details of prop pitch, and gear ratio (any suggestions on how to confirm gear ratio...sorry) this weekend and post again. I would absolutely assume that the previous owner (judging by all of his amazing maintenence and prevention actions) likely changed the prop. It is running really good with the new engine. Sounds great and runs smooth, but I am definitely not getting all she's got. Thanks so much for taking some time out for this.

Re: My Mariah is a dog
 

The Volvo SX outdrive should have a plate riveted to the port side that will show the gear ratio. As far as props, i suspect you will need either a 19" or a 21" assuming you have the 1.43 gear ratio.

Re: My Mariah is a dog
 

OK!!! I finally got to my boat and did a bit of checking.

I am running a Volvo Penta 5.7 GS motor. I also have a Volvo Penta SX outdrive, Type SX-M, and a 1.51 gear ratio. The prop has a QL stamp and the pitch is 14.5 x 19.

I'd love to hear your thoughts after seeing what I am running. Thanks...

Re: My Mariah is a dog
 

First off, your outdrive has the wrong gear ratio for the 5.7 GS as it should be 1.43 so you are going to have to compensate by dropping down to a 15" - 3 blade or maybe a 16" - 4 blade to get those rpms up. Or....change the gear ratio on the outdrive. It almost looks like the outdrive may have been off a 5.0L

Maybe someone else here has another thought....

Re: My Mariah is a dog
 

So I had my maiden voyage for this year and I was running on fairly calm, fresh water lakes. 36-3700 RPM's max WOT. It planed out really well but it was just me and my wife on-board. I guess I am going to get going on trying other props as replacing the outdrive is not an option right now due to cost. As you can tell, I am just learning, so can you help me understand how more RPM's translates into more power rather than just increasing the load on my engine? You anticipate getting out of the water faster with a smaller prop? Seems counter intuitive to me...Thanks

Re: My Mariah is a dog
 

I didn't say a 'smaller' prop, i said one with less 'pitch'. As we advised you earlier, your engine is designed to have WOT rpm's of 4400-4800. When the WOT rpm's are within this range, your engine and prop combination is operating efficiently. Presently you are running a 19" pitch prop. To get your RPM's increased you have to go lower with the pitch and on average a 2" drop in pitch increases your WOT rpm's by 450. If you are presently at 3700 then you need to increase by 900 so you will need a 4" drop in pitch to compensate for that incorrect outdrive gear ratio. Prop diameter does have some effect on performance but you should be able to find a prop with approx 14 1/2 - 15 1/4" in diameter with a 15" pitch and it should improve the performance of your boat. It wont perform as well as a similar boat having a correct outdrive gear ratio (which would handle that 19" pitch prop) but it should be better. Try & find a local prop shop that will let you try one out.