525 efi prop horsepower
 

I finally got a 525 EFI in the shop to run on my prop shaft dyno. This is a 2008 model with approximately 40 hrs. time.

So guys saying a stock 525 EFI is 525 prop horsepower are wrong huh?

That's a little lower than I expected, but numbers don't lie. It's interesting because I've got 2 identical boats here. One with a 496 HO and the other with the 525. I dyno'd the 496 and it made 387 HP at the prop. The 496 boat will run 65 and the 525 will run 70 - side by side. We thought the 525 should be faster with "525" hp. Now we know why it isn't. Maybe this engine is just a little weak. Who knows.

thats a weak 525 or the drive is really tight...

put a pic up of the prop dyno

Having seen other dyno sheets on 525hp's ( old hot boat site), I would a also say is on the weaker side for a 525. Might be up to 30-40hp down.




Darrell.

Every 525 that I have seen or heard about on an engine dyno was between 550-565 hp....and that is quite a few. I am very surprised to see those numbers. I would like to see what another one would do. Bob, any way to test another one to see if it makes the same hp? Thanks for the info.

Eddie

bobl,

Why is the AFR 8.032 all the way across the RPM band...? Was this from a wideband O2 meter? Why were the BSFC readings not listed on the sheet..? What about temp and humidity at the time the run was made..? I have not dynoed a Merc 525 motor, but whenever other engines have been dynoed, I am always curious what the items I mentioned above are as a first glance..

Something seems odd.. I have never seen an AFR reading stay exactly the same across the entire pull on any EFI engine I have ever dynoed, or witnessed dynoed.... Never.. (Maybe some other engine builders can comment on that for starters..) In addition, how was the output at the prop measured..? (I am asking, because I'm not sure how this is done, as I have only measured engine ratings on engine and chassis dynamometers in past)

No sensors were hooked up. Remember this is prop shaft with engine installed in the boat. I was just curios as to the power this engine would produce at the prop. I've already established that an XR drive eats about 10-11% HP. I did a test of a 496 Raylar that made 550 at the flywheel and 490 at the prop. I do agree this engine is a little lower on power than some. The boat performance also is indicative of that. The only other 525 I've tested made 475 at 4900. It had a miss that I was trouble shooting and could not get it to pull past that rpm. Never did get a full pull on it. These are corrected numbers using standard correction factor. I have an electronic weather station that calculates the correction, which was about 1%.

Myself and Mr. Whipple are resolving this power situation though:eek:

Keep in mind that when tested in the boat everything is connected and full water is running through the exhaust. A lot of engine dyno tests are run with dry exhaust. My dyno room is configured for wet exhaust. In fact on the 496 tests I used the entire exhaust system from the boat in order to get accurate data.

WOW...so all 525's are weak.