I'm a bit confused why the fuss over the 5-10 minutes at 5000 rpm's. What is the safe operating range for these motors? I got the boat with 24" Bravo I props. The drives are running a 1.50:1 ratio. I suspected from day 1 that the props were a bit undersized and was planning on putting on 26" labbed props. My thought process was that the higher pitch would lower the rpm's, but the blueprinting would gain rpm's. I figured that this would put me right back at about 5000 rpms. I was under the impression that this was the normal WOT range. If it isn't please let me know before I cause major problems.

Thanks

Maybe I don't understand this performance boating thing, but shouldn't I be able to run at WOT? I had a 26' cruiser with a 7.4MPI and ran at WOT all the time.

Is it possible that I need to go from factory 24" Bravo I's at 5000RPM to 28" labbed Bravo I's to run safely?

I gotta agree with Blue Thunder. Being a mechanic I'm familiar with all those expensive moving parts going up & down inside that engine at 5,000 rpms and I prefer to keep my wide open blasts to a minute or two at best! But .... If its any consolation, and this is certainly a testimony to the durability of the mercruiser engine, I ran in a poker run last year, at 1,000 islands, in my non mechanically inclined friends boat, a 32 foot Fountain with twin 502 mag MPIs, and for 135 miles we ran at WOT - 5,000 rpms ! At one point about 1/2 way thru the run I looked over and said " Are you gonna slow down for a while and give the motors a rest ?" He gave me a funny look and said " Why ? These motors are built to take it. " He then informed me that he runs wide open in all the poker runs he enters. I just kept thinking about the beating those poor motors were taking and all those moving parts going up & down up & down !! But they never skipped a beat !! He also had an extended warranty on the motors, I don't. Maybe that makes a difference.

Bo

On the 5000RPM for 5-10 minute thing, I guess I am just more conservative than most. I feel that is very demanding for a production pleasure boat engine and drive. Even if it is under warranty, it won't always be and you will have to pay the price for your earlier habits. Now, if you are comportable with that, and willing to accept shorter life on your components than have at it. I guess it is a comfort level on how you run your equipment. MY WOT blast are usually just a minute or two. Not only is putting the equipment to the max, but you really have to be on your game as a operator.

You would not believe what they do at the motor assembly plant here in Western N.Y. when they test motors off the assembly line!

Dave,

I would really like to hear that story!!

Bo

I run my 502's WOT during a
poker run. At Lake Cumberland
one leg is 38 miles. Factory
engines can take it. Most home-made engines won't.
That's why factory engines
cost twice as much. I'd rather go 70mph every Saturday and Sunday than 90mph once. Next time you
have one engine running hot,
use both engines to get on
plane, then shut off the hot
one. One will keep you on plane.

Hey Dave;

Thanks for the M.S.D. information. I will put it to good use.

Vinny

SEE-YA ---- It is VERY hard on an engine / drive to keep a boat on plane if the other engine is shut down. Also I would bet that the properly built (home-made ) engine will easily outlive a stock factory engine if both are run at the same rpm and HP. I would put money on that. Factory engines are twice as costly because the factory is gready and covers there poor work with a warrenty. If you are an engine builder than you would already know this.

TinkerBoater-
I am an engine builder. Check
my 604ci 755hp engine for sale in the OSO classified.
Nuff said.