Yes you are right. I am talking about a rebuild with the proper upgrades and computer reprograming.

Ray,

Actually, there is 25hp left in the stock motor. First, the power climbs to 5650 and thats worth 15, and then the timing only goes to 32 at 5400rpm. Motor is happy at 34deg. Also, motor is slightly rich at idle and mid range, but slightly lean at 5000-5600rpm so they need a touch more fuel. Also, timing at lower rpms is extremely low, so torque can really be brought up significantly.

Dustin

How to get there from Here!
 

I would say that a possible 25 horsepower is not a great deal when you consider that you are turning up the rpm from 5350 to 5650 and increasing timing advance on the motor to achieve it. As for the retarded timing at low rpms you and I both know Mercury's fondness for that however thats not going to generate any real high midrange or top end power for these engines at rpms where the timing curves are actually retarding timing as they should from midrange advanced timing.
When you consider that Mercury Racing has had these engines in the field since 2001 with a lot of them in all out racing applications it becomes more important to maintain a little conservatisim in the programming to deliver good reasonable engine life of 300-500 hours. As we all know the HP series engines have always had a mild problem with valve spring life and this is aggravated when the HP525 is going to be run at 300 rpms more on the top end.
Almost any engine can be pushed to the ragged edge for maximum power however most of the time the engine owner will loose valuable reliability and engine life. If they are racing thats a whole other situation and sometimes winning means running at the EDGE!
I feel that if you have an HP525 series engine and you want a significant horsepower increase of lets say 50 to 100HP more then you should be prepared to go into the engine and do some cam, headwork and even consider taking the engine from 502 cubic inches to a 540 cubic inch version and then do the necessary upgrades to the fuel injection system to support the added power. These type of changes will for sure require a reprogram of the ECM to allow a 575HP to 625HP version of this engine to operate reliably at its original 5300-5400 rpm range.
I personaly don't feel any big block chevrolet marine high performance engine should be operated at sustained rpms above 5400 rpms for long periods of operational time without a shaft rocker system and special valve spring packages and valves to keep the valve train stable with this type of endurance usuage. You can do it for awhile, but eventually you are going to pay with a badly damaged engine!
Every performance boater is thrilled with his new found performance until that little bugger grenades!!

Just my two cents and maybe not worth much more.

Best Regards,
Ray @ Raylar

But Ray you told me that it was okay to run my engine at 5999 as long as I didnt' go to 6000....

:party-smiley-004:

Dustin, With your ECM upgrade what fuel can you use? Doug

Just my two cents and maybe not worth much more.

Best Regards,
Ray @ Raylar

Ray.. your 2 cents always worth at least a nickle, and appreciated.

Peter

Very good points Ray, I have to pull the motors next winter anyway to go through them so i figured since they are apart lets bump them up a bit to the 625-650 HP Range, figuired we could do that with some good head work and piston rod combination as well as proper ECM programming and valve train upgrade as well. Just starting to do our research for the best most reliable combination for the money.

Multiple guys have updated the motors with bigger cams, more compresssion and ported heads. Of course more ci also helps so 625 is somewhat easy to achieve. After that, the intake becomes somewhat of a restriction.

Ideally 89 octane, but most get away with 87 octane. 91 is best in my book, since it's only .20 more, but sometimes its not available.

Sorry, but 34deg's is certainly not a ragged edge. The timing table is almost identical to the 500hp efi motor, which had a slightly smaller camshaft and steel heads. They commanded 32deg total at 5400, 29 at 5200. The funny thing is that the base timing was set in the cal for 8deg, but every 500hp efi motor that came out had 10deg base, which gives the motor 2 deg more than what's shown on the scan tool. Meaning they had 31 and 34. Those were proven very, very safe and reliable. Install the bigger cam, aluminum heads and actually your still very conservative.

Many race teams have done similar things by spacing the crank sensor up, which gave the motor more timing. This is only good for 1-3deg's though, and certainly more timing can be run.

Also note, the stock timing table is setup like a carb motor, 12deg's at idle, 32 @ WOT peak rpm. At lower vacuums, they run the same timing. Most motors can run more timing, closer to 36-38deg in low to mid throttle (low to mid vacuum levels) to get better combustion efficiency, higher mileage, less soot and cooler temps.

Thanks,
Dustin