Merc 525sc???
 

Looking at a 99' 38ZX with 525sc's with 35 hours on them. I don't know anything about the engines, and was wondering if someone could shed some light on them for me. Pros, cons, and reliability issues. Also expected performance in a 11500lb boat.
Thanks

IMHO, one of mercs better engines. 454, 177 blower, 5 lbs of boost. The carb they use tends to run rich at idle though. For a blower motor, they are very reliable. Will last a long time if you dont run them WFO all the time. Cruise a low (1-2psi) boost levels and the engines are hardly working.
Downside; heavy boat, hi torque motor, with a bravo I? drive. The drive is going to be the weak point. Expect upper, coupler, and gimbal ring problems.
Gary

always heard good things about the 525

my setup is very similar (not merc) and has been running pretty well so far.

Thanks guys, I have a fear of the stock Bravo 1 myself. I am thinking of using some TCM upgrades to have a more reliable setup. Any other drive suggestions?

Thanks again

as long as you aren't really beating on the drives they aren't going to pop right away. And if they do stock b1s are dirt cheap now because of all the new upgraded drives.

Gary's input I think is right on the button about Bravo's behing your week link.

I boat with a gentelmen every weekend that has a Scarab 29 with a 525SC, it has 260hrs over 4 summers and the thing has run like a swiss clock ever since he baught it new. He takes excellent care of it and only ocasionaly runs it WOT. The only drawback is that he needs to run 93 OCT in it, and sometimes it is hard to find on the water.

525SC...
 

Hey Lonestar...

I have been using three of them in an old 12Klb Scarab for the past four years and have found them to be nearly flawless... I have not had any problem idle wise with the Dominators but sloshing around on a hook seems to dump the bowls after a time for a hard black start... The drives have been no problem either, however, I don't fly the boat, intentionally that is... Just my $.02 but compared to what I read about the EFI folks I am quite happy with the performance... Guess the best thing is being able to adjust and change parts...

Thanks, Karl

I rode in a 1997 42' Fountain "Reggie Signature" with triple 525sc's in it this summer and with 7 guy's a full load of fuel and on flat water it ran 80mph....motors ran smooth and had lot's of torque....my .02.....Fred

I think you will be fine with 91 octane in those engines, merc has backed down on the octane rating on the 575 from 92 to 91 and I believe the book on the 525 also required 92.

A call to merc would confirm that, but am am 90% sure it is correct.

HP 525SC


Mercury HP 525SC Specifications


Propshaft Horsepower: 490/365
Full Throttle RPM Range: 4800-5200
Displacement (CID/CC): 454/7.4
Bore (inches/mm): 4.25/107.9
Stroke (in.)/(mm): 4.00/101.5
Compression Ratio: 7.5:1
Cylinders: V-8
Fuel Requirements: 92 Posted Octane
Drive Unit: Bravo One
Gear Ratio (RH or LH): 1.36:1 or 1.50:1
Length (inches/cm): 47.7/121
Width (inches/cm): 32.75/83
Height (inches/cm): 28/72
Depth: 9-5/8 in. single 13-3/8 in. side by side
Weight (lbs./kg) - Bravo One: 1470/668
Warranty: 1 Year

What is the stock carb on the 525SC?

1050 Dominator

will a boat with 525sc outperform a boat with 500efi's. I didn't know what the difference in power was being one is carb'd and the other is EFI?


Thanks again
Lonestar

i believe you can change pulleys on the 525 and make ita 550hp motor pretty easily so you get an extra 50hp over HP500 so it should move better.

The 525SC will have more low end and mid range torque. Propshaft HP is 490hp.
An innnercooler and pulley change should get you close to 600hp.
The 525sc will loose more hp than the 500efi in very hot and humid conditions.

The 500efi is rated at 470 propshaft hp.
From what I have read, dyno readings show the 500efi's slightly higher at 505-510hp. Also with some of the kits out there, it would be easy to upgrade the hp with an ecm an fuel pressure increase. Also with it being efi, it will be more fuel efficient.

I have a 525sc and it has 330hrs and has never been opened up. It runs great and only uses a quart of oil every 20 or so hours. I might open it up for a valve job and springs over the winter.

If I had my choice, I would probably take the 500efi. Easier to upgrade to more hp and newer technology.

Wasn't the 525 basically a 454 mag with a 155 blower??
If so, how would a 502 mag do with a 155 blower??

its had lower compression pistons and a different camshaft than the 454 mag. and a 177 blower.

The only real differences are the pistons are 7.5:1, the cam is a slightly different, and the ignition timing curve is slightly different. The blower is a Wiend 177.

The main concensus I have seen is the 177 is too small for a 502 and a 250 is a better choice. The 575sc is a 502 and uses a Wiend 256 blower.

In my opinon the 525SC was the best Merc HP series motor made...second was the 454Mag.
I ran the $hit out of them for 3 seasons with a total of 470 hrs before doin a rebuild.

I had a pair in a obsession cat. I replaced the small blowers with a pair of whipples and picked up almost 20mph. I used the same carbs, 1050 dominators, and re-jetted it smaller, 92 prim, 96 sec, from the 99 jets it comes with. A big difference with the whipples.

I am using Teague Platinum XZ drives after both B1's on my 2000 382 Formula snapped the forward gear. No more idle home for me :cool: