565s short on Rpms
 

Down at LOTO trying out our new ride. We have ran the boat down to low on fuel with also cold air temps. The max Rpm I can get is 5000 at 83mph. The VV7 tach needle starts to turn red if it gets to 5000 Rpm. Can this cause the motor to go into Guardian mode. There are no alarms going off. There are from what I've heard silent codes that can just reduce power? These are the same props and setup from the previous owner. They are in perfect condition.

2014 Active Thunder 33 Evolution
565s turning Labbed 32 Maximus props with XR Sport Drive 1.50

Just to clarify you are trying to determine the performance expectations of a new to you boat, and not resolve a newly developed problem on a known boat?

Have seen a GPS reading of 92.

If you ran your tanks really low I'd start with checking your fuel filters.

scan the engine while running and verify rpms in the scan and available power - If it is reporting 100 % available power then ONE IS NOT in any form of guardian mode. Its that simple of a test - if is showing less than 100 % you have a form % of guardian mode - hence continue looking in the scan for faults and or out spec parameters.


Next is check proper fuel pressure readings while running all rpms - fuel pumps hate to be ran low or out of gas.

Change the fuel filters and check for water & crap in the fuel

Props and or any damage on the blades ?

Bottom growth and or growth on the lower unit and props ??

Is the boat carrying any extra weight ???

Next the 8.7 565 runs on 89 octane and MAX rpm is 5400.

How old is the fuel and octane level ?

Is the fuel vent venting properly ? especially from a boat that sat over the winter ??

Next is the flame arrestors clean both of them ? also if you open up the engine hatch 6 or 8 inches while running the boat does it pick up rpms ???

Boat was just filled up with new premium fuel. There's no growth on anything. The props don't have a scratch on them. There is no extra weight in the boat. I will check the fuel pressure if it ever stops raining here.

Thanks,
Jeff

Boat/setup may like snotty water. Those are some big wheels managing a wall of water in the glass. Wait for the weekend in the main channel and see if you touch the 90s.

Was the 92 at sea level ? I can't get mine to go what It did in saltwater

Was the 92 with you in the boat with the same props ? Or is this what the previous owner told you ? Have to ask and get this out of the way...

5000RPM and 83mph, is roughly 18% slip. To hit 92 with those props, you'll need to turn around 5600rpm if the slip remained constant. Is it trimmed properly? Tabs dragging?

Trimmed properly, the 92 was at sea level. The max RPM is 5400. That would hopefully be around 90 at the correct Rpm.

32 maximus 5 blade is one hell of alot of prop to turn with 565 hp, i think everything would have to be perfect, as air, low fuel, loose water etc, just my opinion

Thanks, Arctic friends. That's 565s are we times two. We're coming from a 2005 30 Outlaw with 496 HOs spinning 30 Labbed four blades. I know Maximus are much harder to pull.

was everything the same as it is now,espically asking if it had the same props.

I'd call Pat at AT and ask him about trim settings.
I just don't see why both engines would go into any guardian mode at the same time.
With 565's and all available power, you should easily hit 90. The 525EFI 33 AT was over 90mph.

What's saltwater good for.....2-3mph.......Still wierd.

Drives toed in correctly still?

Sorry, had to put this here.... Some labbed 32's would make it fly! :party-smiley-048:

Other than running it out, at least you're boating this week!

I'm with smitty on this...don't see those engine's having enough a$$ to turn those props...

time for him to lose the fat girls and pick up some fountain skanks,,:D

Looks like no engine issues. We saw 86 mph yesterday. I dint catch the Rpms, with a little more playing with triming angle. I could have ran it out longer but a few stray cruiser wakes around. Will try to get to 5400 Rpm today before going on trailer to back home. The short sport drives don't like to be trimmed much. Thanks, for the replys.

Merc 565s are equivalent to 600hp aftermarket Dyno standards

I fully understand that, when you dyno a merc engine at j607 you see #s 3.9% higher. I also know a maximus acts like a taller prop, thats why i mentioned it. To me it would be like trying to turn 34 pitch props. I tried a 28 maximus on my Baja once, it ran almost 90 mph w 1.5 gears before it sheared off the prop shaft, i would think if you could spin 32 maximus props at their 8%prop slip i would think youd be going over a 100, i havent looked at a prop slip calulator though

So running the numbers thru the prop slip calculator tells me at 10% slip at 5400 boat would be going 98mph so either the props would have to be cut down and labbed quite a bit to get slip way up or engine would never hit its peak rpms unless boat ran close to 100 mph, are the new active thunders really fast hulls, could it run those numbers w 600 hp?

Idk. The OL 36 could run almost 100 with 565s. The latest 39 velocity could too.

Set your throttles at 3000 rpm, and start playing with drive trim, starting at neutral.
Watch the decimals on your GPS speedo. I think you will find that boat to be the fastest at neutral trim or slightly above.