Max WOT on a 496HO
 

Hey guys.. I've been doing some testing on the new boat.

It has a 496HO in her and I currently am seeing 61/62 mph on the GPS.
The previous owner said he saw 65.
I am assuming that he was referring to the speedo and not the GPS.
While the GPS blips between 61/62 the speedo reads 65-66 (understandable).
I do have a smart craft system monitor gauge on-board and I noticed at WOT I am only seeing 4750-4775rmps. It's a bravo 3 with dual 26props.

I Know Merc rates the motor from 4600-5000 max rpm. Should I be seeing another couple hundred RPMs? Do these motors make power all the way to 5000 or am I am the falloff point where I am?

Trying to squeeze every last pony and mph I can. :ernaehrung004:
It's a stock 425hp 496HO
Thanks!

Prop work.

you can spin that motor to 5400rpm no problem....lab those props and you will gain 300rpm....that should put you wheere you want to be....call brett at bblades he did mine

??? The rev limiter is 5150 on a stock 496HO.

ECM can be sent in to raise it.

It's only going to go so fast and turn so many RPM for the boat it's in. It's well with in the range merc rates it at. Probably makes power to 5K but your just not going to see it with those props. You can try different props but in the end your probably only going to see a couple mph difference if any and a thinner wallet.

What kind of boat is it?

It's not a good idea to raise the limiter and prop that engine to 5400.

Even if you do, the torque curve won't hold up to allow you to actually "use" the additional 200 + rpm.

So you will spin the props faster after you set the limiter higher and you won't see anything worth the effort.

If you are leaving the engine stock, the best bet is to prop the boat/engine to 5100 and leave it at that. This will be your cheapest, most noticeable gain.

This all of course is leaving the other "half" of the conversation out of it (the boat).

If you insist on bumping it up to 5400 with no other upgrades you will most likely regret that decison unless you sell the boat soon after.
It would be good however, to adjust the setup so that you are running the engine at or very near the rev limiter at wot.

This horse has been beaten before if I remember.

Prop it to where you are bumping the rev limiter warning buzzer in ideal conditions.

Bob Lloyd of Full Throttle has dyno specs of stock 496 MAG and MAG HO's. They make their peak HP at about 4,700 and 4,900 RPM respectively. The only thing you will gain by raising the rev limiter to 5,400 RPM is a lighter wallet.

I poked around a little on this and it looks like the truth is right in the middle! Peak HP is at 5,000 RPM according to Full Throttle Marine: http://www.fullthrottlemarine.com/49...%20Article.htm

hey guys-

It's in a 06 Cobalt 240. I had it out again yesterday in pretty good conditions and it was the same thing.
If peak power is at 5000rpms, I am not getting there.
The motor will remain in stock trim for quite some time. (light wallet after buying this one!) Maybe some headers next season.
I would imagine the difference in HP at 4775 and 5000 isn't all that much but heck, if I have a little extra sitting there I want it.
The boat runs great and sounds fantastic with the captains call open.
I came from a 5.7Merc in my last boat and the difference is unreal.
What would you guy recommend doing to props other than maybe dropping to a pair of 24's to pick a few hundred rpms?
Thanks

Notice torque starts to fall off past 4,900 RPM on the HO stock. That is probably what I rememberd from those dyno sheets. Been awhile since I looked at them.

Where are you located? Hot, humid weather will reduce RPMs on any motor. Perhaps the previous owner was getting 5K rpms on a cool dry day? I propped my 496HO for 5K rpms, it would turn + or - a few RPMs depending on the weather.

I'd leave it stock and enjoy it, save your money.

Not bad advice Dave...
I am in Chicago. While the weather can get pretty hot and humid at times, it's been ideal lately. It was about 75 on very low humidity the last time I tested it.
I did notice on the dyno graphs posted in the link that on a stock 496HO with stock exhaust, there was about a 7 to 8 HP difference between 4750 (where my max rpm is) and 5000 where it made peak power.

just bc you set the limiter at 5400 doesnt mean that the engine will spin to 5400....lab the props to gain 200-400 rpm and you will probably be at 5000-5200 at max throttle without hitting the limiter in the computer,,,whipple can flash the computer for you ,,, and bblades is an expert on bravo 3 props. then enjoy your boat...you probably will only see a gain of 3-5mph at best

Cj240:

Listen to what most other people are telling you here on this post.
The rev-limit on a stock 496HO is set at 5150rpms for a reason. The stock heavy clunker valves and weak springs cannot take more than that for long periods that this engine is subjected to in boating, so:"DON'T GO THERE!!"
As for squeaking some more rpms and matching good 5000rpms to your boats top speed, do some prop work -maybe labbing and get the rpms there and that will be about all you will ever see without going into the engine with mods like our Raylar kits or possibly 1-2 mph that you may gain from a good header kit like Dana , CMI Sporttubes or Hardin Marine long tubes.
As some have said, save your money, enjoy the summer boating and make meaningful and safe upgrades when you can in the future.
You also need to remember the Cobalt hulls are big and heavy for their size only a 22 degree-V, I believe and are never going to be really fast performance boats as they are considered more a sport performance cruiser.

Best Regards,
Ray @ Raylar

Thanks Ray-

I have to agree. I have no major complaints with this baby. For a heavy 24 footer that throws one hell of a wake for boarding and effortlessly runs into the low 60's on the gps that's not to bad.
I wouldn't mind working the props to see max HP right at 5000.
I'll be giving you a call to talk about headers when I am ready.
I recently heard a 496 with Dana headers/thru hull exhaust and it was definitely a different sound.. Very nice indeed..

Forget the headers on the 496. The stock manifolds flow very well. You either go ALL in on a 496, or leave it alone period.
Great engines in stock form that are turn key reliable hour after many hours. Going at it a piece at a time is only going to cost you reliability and aggravation.

Get your props either worked or drop a pitch to put your RPM's in line with your typical load and/or conditions.

Word