Reply With QuoteI will borrow a 22p and see what happens, but I think before I bought it they ran a 22 and the RPM were to high.
It is a 05' 260 Checkmate ZT
Ok, I am running the 496 mag, I am spinning a Bravo 1-24 pitch, I was running about 4700 RPM.
Mine originally had a 24P on it. Mind you, I am running 30 feet and an HO, not standard mag. I was seeing around 48-4900. Took a little while for the nose to roll over on plane.
I got a 22P (smallest Merc Bravo-1 4-blade) and am right around 5100, a lot nicer out of the hole - boat rolls right over on alot less throttle. My speed picked up from 61-62 to 64-65.
I still have my 24P in case I bring the HP up to pull it. But, I run the 22 for all around fun. Oh, and the motor is stock but pulled the turbulators.
I would borrow a 22P and see how you like it on the boat. If you end up doing that and like it, hang on to your labbed prop. You may need it some day.
EDIT: BTW, what boat is that?
I will borrow a 22p and see what happens, but I think before I bought it they ran a 22 and the RPM were to high.
It is a 05' 260 Checkmate ZT
Ah, you know, I believe the Mag has a 4900 rev limit - as opposed to the HO having 5150. Therefore, you may be right.
With a Mag, you may be at the limit - short of pulling it apart, doing the heads and adding a cam. Plus getting the ECM reprogrammed for all of that.
You would still be cheaper than a whole new motor, though. Adding exhaust would be a nice first step. You could always use them later if you mod the motor.
does the 496 HO have the turbulators in it? What are they supposed to be there for?
does the 496 HO have the turbulators in it? What are they supposed to be there for?
Yes they all have Turbulators.Some claim that they prevent water reversion.
But inside the ends of your exhaust you should have rubber flappers plus chances are you will have rubber external flappers and with the big s bend in most 496 exhaust i wouldn't worry about reversion.Unless you drive your boat in reverse.
I enedend up installing REX stainless internal flappers in my tips and eliminating the external rubber flappers altogether.
cool, I don't own the boat yet, I'm test driving it this afternoon. It has 112 hours, any other tips, tricks or stuff to look for?
The turbulators do cost HP but be careful, they are designed to stop reversion. Not from lake water but from the water exiting the engine mixing with the exhaust while the engine is running at idle. This is Mercs way of helping reduce the possibility of reversion because the head pipes need to be longer and mix water/exhaust further away from the manifold. They are designed to catch the water and turn it into steam so it does not enter the cylinder.
The CMI exhaust is the best option for HP but they are pricey. CMI claims 481 HP with their exhaust and we have seen good performance improvements with them.
Shadow is right. You made a change to the prop and lost RPM's. Fix that problem before going any further.
The turbulators do cost HP but be careful, they are designed to stop reversion. Not from lake water but from the water exiting the engine mixing with the exhaust while the engine is running at idle. This is Mercs way of helping reduce the possibility of reversion because the head pipes need to be longer and mix water/exhaust further away from the manifold. They are designed to catch the water and turn it into steam so it does not enter the cylinder.
The CMI exhaust is the best option for HP but they are pricey. CMI claims 481 HP with their exhaust and we have seen good performance improvements with them.
Shadow is right. You made a change to the prop and lost RPM's. Fix that problem before going any further.
Good info to know! From a reliable source.
Good info to know! From a reliable source.
What's up D? Hope everything is good with you. The HO has more overlap so it is something to watch for. It's like everything. We have seen some with signs of reversion on the spark plugs (rust, or water droplets when checked immediately after running) when the turbulator is removed, but we have also seen some with no problems at all!!!
If the exhaust tips are under the swim step and there is an "S" pipe from the tail pipe to the tip, or if there is a muffling device, there is more of a chance of reversion.
The water / exhaust mixture actually pulsates back and forth in the riser pipe due to the camshaft overlap. The more back pressure, (low exhaut tips or mufflers) the more chance of the mixture working its way past the bend and ito the manifold. At this point it will enter the cylinders.
If you remove them I suggest letting it idle in the water, pull a couple of plugs and keep an eye on it.
Thanks for your input.My turbulators have been out since last season.since i just went through my motor i think i'll pull a couple plugs next time out just for the hell of it.
By the way i've got an aftermarket cam,heads and valve train.Don't think i've got any indication of reversion but what the hell i will double check.Better safe than sorry.
we should be out just about every weekend starting the the next couple of weeks through the summer.Hope to see you out there.
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