If you plan to do mods in the future I would say the 502, it has better internals. If you boat in saltwater the closed cooling would be better. The HO motor even though its only rated at 10hp more seems to run 1-3 mph faster in your average single engine boat in stock form. Just the first few reasons of many to think about...

 

The 502 has many less expensive modifications readily available.

Why 502, Go 454 MAG, lighter and great revs, change the exhaust and you've 502 power output plus you save 100 + lbs. Change the regulator, injectors, arrestor, etc and you get even more. Plus you can supercharge. I love the 454 Mag................... However, if your boat is big, there's no replacement for displacement, so go 600...................

 

Good point dallas, I always forget about the 454 mag.

 

I like the 502 personally just because of the forged internals, but if I was in salt I would want the closed cooling.

Not to get this thread off course, but I have been thinking about this. Usually a 496 HO is just as fast or faster than a 502 mag in the same boat. Yet the experts(Raylar, Tyler Crockett, etc) state the 496 is about 425-430 hp AT THE CRANK. It's my understanding that the 502 mags were 415 at the prop. Meaning the 502 SHOULD have more hp than the 496 HO. Were the 502 and 454 mags hp over-rated from Merc?

 

blackhawk - probably another case where peak hp does not tell you everything.

My guess without seeing the dyno sheets is the 496 has more "ZING."

 

When I was shopping for a 288 it seemed on average the 496ho boats were 2-3 mph faster then the 502 boats. It seems to me maybe the 496ho is underated but thats just opinion based on what I know about motors which isnt much....

 

Bottom line is if your going to modify your motor in the future..... 502.

If no mods are planned and you want a good reliable motor (not saying the 502 isn't reliable) the 496HO is THE way to go. Closed cooling is very nice, plus, the sensors and monitoring system are a definate bonus as well......

In my opinion the 496HO is a very underated motor. You get pretty darn good performance and reliability with totaly breaking the bank. I know that my 496HO has started EVERY TIME I have turned the key...

It's that simple.....

 

blackhawk - probably another case where peak hp does not tell you everything.

My guess without seeing the dyno sheets is the 496 has more "ZING."

cfm for acceleration I would agree. But for top speed it would SEEM that similar motors(ci and rpm range) the higher hp motor would have more top speed. But then again I am no expert!

 

When I was shopping for a 288 it seemed on average the 496ho boats were 2-3 mph faster then the 502 boats. It seems to me maybe the 496ho is underated but thats just opinion based on what I know about motors which isnt much....

That's just it if anything according to dyno sheets they are over-rated. I noticed also that Merc no longer advertises these motors with PROP SHAFT hp.

I heard that Merc allows the black motors to have a much higher % for +/- hp ratings, like 10% if I remember right. So, that would mean a 502 could only have 375 at the prop and still fall within the parameters. Maybe all the 502s were really closer to 415 at the crank? Just thinking out loud.

 

Would a NA 350cid with 435hp go as fast in the same size boat ?

Zing baby.

 

Would a NA 350cid with 435hp go as fast in the same size boat ?

Zing baby.

If it had the exact same torque and hp curve! And I said "similar" motors.

And could you give me the technical definition of "zing"? Is this something that I can add to my gas?

I guess my point is Merc first rated the 496HO at 425hp at the prop. But all the sudden these dyno reports come out saying they are 425-430 at the crank yet they seem to push boats just as fast or faster than a 502 mag which was rated at 415 at the prop(445 at the crank). Things that make you go hmmmmm.

 

The Merc 8.1L496 and the Merc 502MPI really aren't similar motors. Don't let the 6cid difference make them seem more similar than they are.

Zing is a new word I use to differentiate a motor that is faster than another even if they dyno at same power on the same dyno.

Zing !!!!

 

Zing is a new word I use to differentiate a motor that is faster than another even if they dyno at same power on the same dyno.

Zing !!!!

I like it! Next time someone askes me how much HP I have im gonna tell em......not sure but it sure has some ZING huh...? :laugher:


Also just thinking out loud, people have told me the 496ho's are more efficient and get better gas milage too.....no real data to back that up though.

 

Gotta love the internet! Did some quick searches and it appears that most 502 mags (that were rated at 415 at the prop) dynoed in the 400hp range at the crank.


Now I can sleep tonight!

 

It makes sense when you consider how many people have swapped out 502 mags to HP500s and picked up substantial top-speed and acceleration. Since the HP500 is rated lower than actual hp and the 502mag is rated higher the 55 hp difference is probably much(100+?) more!!!

 

HP500 has way better valve events, valve lifts, heads, induction system, + exhaust, . Therefore, it's got a ton more ZING.

BTW: A 502MPI can be categorized as BLAH. Sure, it has 400 or so HP, but it is just purely and blatantly BLAH. No ZING what so ever. :laugher:

 

ZING=the Anti-BLAH.

 

Wait until we get into "Zing-a-Ling" and then progress further into "Zing-a-Ling-Ding."

When we finally reach "Zing-a-Ling-Ding" then the whole world will just make sense. I'm just not sure this is reachable though. Hopefully sometime though.

 

Why 502, Go 454 MAG, lighter and great revs, change the exhaust and you've 502 power output plus you save 100 + lbs.

Isn't the 502 and 454 made from the same block? I don't see the weight savings.

 

Referring to the exhaust. Also, I beleive the motor is lighter than the stock 502.............. and yes, you can put the same exhaust to the 502. (talking about aftermarket exhaust if It's not clear, sorry)

 

I had a boat with a 502 mag, blew it up, replaced it with a 454 mag and did the exact same rpm and speed. I also had a boat with twin 496 mags and one with 496ho's and i'll tell you one thing, when your stuck, forget about fixing it, the damn things are to computerized. I was stuck once because a manifold temp sender was reading improperly and it put the boat in guardian mode, pain in the ***.......had to wait 4 days for someone to come with a computer to find out a $20 part was chitting the bed....... I'll take a 502 or 454 anyday, salt or not, as long as you can flush it..... Just my opinion...........

 

Dallas - really not trying to step on toes but a 454 385HP Mag over a 502Mag ?

It's not weight. It's not power.

Only thing I can think of is price. other than that, take the 502 everytime.

My 02

 

Isn't the 502 and 454 made from the same block?

NO !!!!!

502 is it's own block. It has siamesed bores to handle the 4.47" + bores.

454 is non siamesed and handles 4.25" bores. You can take these to about .100" further but no where near the 4.47"

Same exterior size - same heads, exhaust, and etc, etc. But not the same engine block.

Oh, weight is negligable between the two.

 

Dallas - really not trying to step on toes but a 454 385HP Mag over a 502Mag ?

It's not weight. It's not power.

Only thing I can think of is price. other than that, take the 502 everytime.

My 02

My 502 Mag longblock was $100 CHEAPER than the 454 Mag longblock. Guess I screwed up. I shoulda bought the 454.

 

I believe all the parts are interchangeble between the 454 and the 502, other than the obvious pistons and crank.