Need for Speed in the Outback

[jmondl]

So, this past weekend I was working on some barefooting behind my 2010 Outback DD 325 hp, and needed about 43+ mph. However, the Outback peaked at about 42 mph pulling me barefoot. When I later opened the boat up without pulling anyone, the boat topped out at 44 mph at about 4400 RPM. I know I can replace the prop, which I probably will, but I was surprised the engine refused to push past 4400 RPM. My last boat (V-6 190 hp) hit over 5000 RPM. Will a different prop increase the top RPM, or is there another trick, or is this just the normal RPM of the engine? If anyone has other insight into picking up a few more MPH without losing too much hole-shot, I welcome the advice.

[jmondl]

I just checked Inmar's website, and they claim the Assault 325 has a max RPM of 5000. To make sure this issue is design related and not a problem with my boat in particular, I wonder if other Outback DD owners could weigh in on their boat's top speed. Thanks.

[Hoopskier]

I just checked Inmar's website, and they claim the Assault 325 has a max RPM of 5000. To make sure this issue is design related and not a problem with my boat in particular, I wonder if other Outback DD owners could weigh in on their boat's top speed. Thanks.

Although my boat is a few years older, it should be similar. I have the Assault TBI which has a top RPM of 4800. I have a 13x13 3 Blade OJ Legend prop and my top RPM is about 4600, pretty much on target for my boat/engine. I don't know what the top end speed is, guess of low to mid 40's, but based on the RPMs are top out with the current prop, I know that it is as fast as it will go. I had a 13x13 4 blade and the engine would bump the rev. limiter at WOT.

A prop change might help you out and get your RPMs your missing, but you have to know what your starting with as well. What prop do you have on it? Do you have any ballast or wakeplate on your boat? I don't have either so it a non issue for me. Only other trick is to keep the boat as light as you can-no extra riders.

[maxpower220]

I have an 08 Outback with the 325. I am lucky to get 41 while barefooting with a couple of people in the boat. It is very disappointing if you like to barefoot. I think the only solution is the 6.0L engine. There is just too much surface area in this boat to really get much faster.

[you da man]

Sounds like they need to bust out the old school outboard barefoot boats

[cab13367]

Wow, I am finding the responses surprising. With about the same engine, I thought the Outbacks had significantly higher top ends due to being lighter, having a shallower V, 1:1 drive ratio, and little/(no?) drivetrain loss.

My 2006 LSV with the 325 Assuault runs 41 GPS-verified mph at 5000 rpm.

[jmondl]

What prop do you have on it? Do you have any ballast or wakeplate on your boat? I don't have either so it a non issue for me. Only other trick is to keep the boat as light as you can-no extra riders.

I am not sure which prop I have, as the numbers are hidden by the nut on the shaft. It's a 3-blade prop, and the numbers on the side of the prop are "OJ 10 07". OJ's website does not indicate which prop that might be, or at least I have not been able to figure that out.

When I was being pulled barefoot, I only had a 130# driver; when I opened it up without pulling anyone, I had only me and young son: total weight about 210#. I had no ballast on either occasion. I do run with the wakeplate down, which I assume flattens the wake. Maybe I should try running with the wake plate up.

[deerfield]

jm - Indmar owner manual, Appendix B, Engine Specifications, states that the operating range at WOT on the 5.7L carbureted engine is 4400 - 4800 RPM. Even though listed up front in the manual and is the engine in my 2007 Outback DD, no mention in Appendix B of the operating range at WOT for the 5.7L 325 EFI Assault engine. Regarding the factory prop, I tried to get specs from the USA Water ski web site. No luck. It posts prop specs only on the 2010 models it approved for three-event towing, which does not include Outback. Most recent model year Outback was approved was 2009. I have the factory 3-blade prop. Top end speed on my Outback is 44 MPH. Don't know the RPM because just not watching it. Boat is about 4 MPH slower on top end compared to my old Ski Nautique, which is disappointing. Still, hole shot is strong and plenty of torque to hold speed. Have not tried barefooting (even though I did buy a barefoot boom). - Deerfield

[Laz]

I switched to an ACME 13x12 (Part #541). My top speed is now 46 mph by GPS. I don't know what the RPM is at that speed.

[cab13367]

I do run with the wakeplate down, which I assume flattens the wake. Maybe I should try running with the wake plate up.

Yeah, try raising the wakeplate up until it starts porpoising, then tap it down just enough to settle the bow. That should be good for a few mph more.

If you are getting only 4400 rpm and you need more top speed for 'footing, then you should think about getting a numerically lower pitched prop. Basically, you want the highest pitched prop that will allow your boat to still get to 5000 rpm with your boat loaded the way you would have it loaded typically. Suggest you call nettleprops.com directly and he can suggest the right prop. Then, if it doesn't work as he describes, you can send it back and try another one for no additional cost.