Young Performance

Nice looking piece Ray. Is it casted?

One other thing I forgot to mention is that these 3 500's I did were 516 ci. One had been rebuilt and was already at 4.500. It was poorly finished and too large to go back at that bore. So, in order to keep them all the same, I bored them all to 4.530 (516 ci).
Eddie

onesickpantera

Ray is incorrect. Black motors are always rated at the prop(and usually over rated) and blue motors are always at the crank(and usually under rated).

The HP500 was rated at 500 hp at the crank and 470 at the prop and usually dynoed a couple ticks over 500.

The 502 mag was 415 hp at the prop and usually dynoed about 430 at the crank(should be 445 using merc's math of 30hp loss). 496HO was rated at 425 at the prop. Both engines were over rated.

The 525 usually dynos at 550hp just because it is an under rated motor. It is not rated at the prop.

Young Performance

[QUOTE=articfriends;3546581]Lets get a few things straight: a STOCK hp 500 makes 505-510 hp at the crankshaft and that is using the sae J-1349 dyno correction factor. Every performance shop except for most oems uses j-607 which will typically give you hp numbers that are more generous to the tune of 5 %, to the average guy this sounds real technical and confusing BUT what it really means is that 510 hp that merc gets magically turns into 535 hp on most dynos using the older, more generous J-607. Add some dry headers which should be worth 25 hp that hp number now becomes 560 hp, so a fresh stock merc hp 500 with dry headers on a dyno is now a "560 hp" motor even though NOTHING has been really changed. Add a better cam, bigger throttle body and a set of Merlin heads , which by the way ONLY flow about 1.3% better at .600 lift intake/4% better at .600 lift exhaust (un-ported): (merlin Grumpy Jenkins 310's vs GM 990 317's))
http://users.erols.com/srweiss/table...hevy_Big_Block
and I wouldn't be surprised if that 560hp could become 600-610 hp. Now, if a guy had some high hour hp 500's and they weren't putting out the hp like they did when they were new , yes, the boat would pick up a decent amount of speed but without investing in a seriously performing head don't expect a ACTUAL 100 plus hp change, Smitty


I agree with you. I didn't claim to have added 100 hp, just that these made 599 hp with dyno headers and all accessories. By the way, these were the 325 Merlins, not the 310 Grumpy's, for what it's worth. We actually weren't even looking to make that much. I didn't think they would. It was mainly just a freshen up with a few needed changes. These were some of the best ones that I had done with a 500 intake. God knows I did a few wrong ones where the combo just didn't work.
I expected more out of the one with aluminum heads. I was very dissappointed that it only made 550 hp. It took quite a bit of playing and poking to even get that. I considered that one a failure.
I had done a few in the past that were more inches, but didn't make any more power. It seemed that the smaller inch engines did better with that intake. I did some 555's with 345 aluminum heads, 10:1, fairly aggressive cam, etc. and it barely broke 600 hp. It was a tub of chit. I don't know if the combo was that bad or if the intake just couldn't support that many inches. Either way, it pulled to about 4500 and fell flat on it's face. I couldn't stop it from going pig rich past that and just puffing black smoke out the pipes. I played with it for 2 days on the dyno and nothing made it any better. I think the best it did was 610 hp. I was embaressed. I ended up pulling the intake and using the Holley setup. I swapped the intake on the dyno and the first pull it made an additional 85 hp. It ended up at 710 hp. Big difference from the 600 hp with the 500 intake. I learned a lot from those mistakes.
Anyway, the customer is happy and the boat is running faster than it ever has, so that's all the matters in the end. It doesn't matter what I think. I have had some that made good power and other that didn't when it comes to the 500 intake.
Eddie

articfriends

If you read my post I was essentially saying that the hp 500made 505-510 hp stock at the crank and used Raylar for reference. As far as what they make at the prop, I didn't really care in this instance and should have just left that off. My contention is it isn't real easy to make 600 hp from a hp 500 by bolting Merlin heads on,swapping the cam and bolting on a better throttle body unless you are running dry headers in that case you started at 550-560 hp anyways between the j607 correction factor and everything else, Smitty

45SS

The engines are in my boat. It is substantially quicker and faster. I do have to change the props, it currently runs 28 pitch props. I don't feel that the boat was that down on power to start with, two of the three had never been out of the boat.(11 years) They may have been down on power, but they were not leaking or blowing oil out of the breathers. The boat would plane and run just fine. They were in the 500 hour range.The Mercury tech that installed the engines was very impressed on the sea trial. His personal boat is a 35 Fountian with 575's. Eddie is comming in the spring to do the in water tune. I am going to get a set of stock untouched 32 pitch props from another 45 Sonic. It has 575 untouched engines. We will see if it will pull them , and if so we will post the numbers. The boat does have GPS. The best numbers ever run in this boat by the previous ower was 83 GPS. Reguardless of the out come I would ask for the same combo package from Eddie. I was there during the dyno session. I AM VERY HAPPY WITH THE OUTCOME. Happy customers are what any bussiness would want. Young performance has one with me.

JaayTeee

A friend of mine had his refreshed a couple years ago, they did Dyno them, they made 521 hp. ( I have a copy of the dyno sheet somewhere)

I watched one with approx 500 hrs being dyno'ed, to
get a baseline before rebuild, 3 pulls, 525, 531, 545, as I recall, this was december, no humidity.

We rebuilt and did some upgrades on a pair this spring,
Dart Pro One's, bigger cam, mono blade, ecm, 575 is
all we could get out of them.

We have slight ECM tuning issue to hash out, but I doubt
were going to find 25 more hp out of them.

onesickpantera

Smitty, I wasn't disagreeing with your post, just pointing out that black motors are rated at the prop and blue at the crank. That's why I only quoted that part.

Did you get my last PM?

Knot 4 Me

This is exactly opposite of what I was told by a Merc rep. Black at the crank, blue at the prop. Dyno testing of both types of motors tends to back this up.

onesickpantera

496HO was listed at 425 propshaft hp. 502 mag was listed at 415 propshaft hp. HP500 was 500hp at the crank and merc rated it at 470 at the prop. If they rated it at the prop it would have been called a HP470.

Now, I totally agree that dyno numbers don't back this up as the blue motors always have more hp than rated and the black less. I think the confusion really started with the 525 since it put out so much more hp than advertised.

If you go to Merc sterndrives specs right now they are all listed with prop hp ratings, the new 8.2L HO is listed at 430 propshaft hp. If you go to Merc Racing sterndrives they give crank hp.

bobl

Didn't mean to start any kind of conflict, just discussion. I'm not sure how Merc rates what. It's all marketing anyway. I know that Merc advertised prop hp for several years on all the engines, blue and black. Then they quit saying prop hp altogether. Maybe because the black motors were not very close to those numbers. Here are some I've actually dyno'd at the prop. 496 mag 353-365, Mag HO 387-392, 502 Mag - 390, Raylar 525/496 - 492, 525 efi 475-508, Teague 800 720
This is using "standard" correction and a weather station to get atmospherics. Using the SAE correction that Merc uses would have resulted in 3-4% lower readings.

Bob Lloyd
Full Throttle Marine