Mercury 525 SC

[sellsman11]

Can some of you guys share rebuild recommendations for Mercury 525SC's. I dont have alot of experience with them.

The motor in question has 397 hours. Meticulous maintenance has been performed but the motor has never been gone through.

Thoughts?

 

[mdgperf]

The merc 525sc a great motor that can go some hrs,454 low compression,low boost,I would recommend a complete overhaul and upgrade the cam to a hydraulic roller thats if the motor was run in fresh water,if the engine was run in heavy salt probably better off running it till she blows,i would also send the blower off to the blower shop for a rebuild,i have upgraded-freshed several 525sc to the 600hp level,great engines just burn more fuel than todays na engines making the same hp

 

[OldSchool]

Dave,
Correct me if I am wrong, but isn't the 525sc basically the same long block components as the 420 with a small blower added. All forged stuff, right?

 

[mdgperf]

Pretty much the same engine except 7.5 compression,compared to 8.6,same cam,crank,rods,block engines held up real well,they would wipe a cam lobe once in a while(as would all flat tappet cams back then)the 454 like supercharging non siamese block has good cooling around cyclinders,use to run a blown-intercooled 454 12lb boost,pump fuel in my 28 pantera loved 6000rpm,bravos didn't care for it much

 

[MahopacMarine]

Can some of you guys share rebuild recommendations for Mercury 525SC's. I dont have alot of experience with them.

The motor in question has 397 hours. Meticulous maintenance has been performed but the motor has never been gone through.

Thoughts?

Give Charlie a call tomorrow or talk to Rick.
They have done quite a few. I'm no engine tech so I cant speak on that. :blush5:

Tom

 

[Griff]

The stock intakes do not like salt at all. Mine had some salt usage in its first 200hrs of life and I had to have some of the water ports welded. I did a top end refresh on mine at 340hrs. All looked good except a cracked Gil manifold had caused some pitting on an exhaust valve. I upgraded to a Crane 731 cam and picked up about 150rpms. I ran almost 8# of non innercooled boost for about 300hrs. and then sold the boat to Dude Sweet. It was still running strong when DS pulled it at 500hrs for bigger power. I agree, its probably a good idea to have the blower gone through. I never had mine done, but I changed the lube about every 30hrs.

 

[HaxbySpeed]

The ones I have done also had substantial pitting at the T-stat housing from salt water. Like everyone else said go hydraulic roller if in the budget. I like to bump the compression and stay with low boost to keep the little blower happy. They were really conservative from the factory and liked about 4 jets pulled out of each end. Send the blower to Eric, and drive er hard. :cheers2:

This one is stock cam, edelbrock ovals out of the box and 8.5:1 @ 4.5lbs

 

[glassdave]

I have a pair with about 250 trouble free hours and they've have had excellent maintenance. I was told once that the stock blowers could develop some sort of issue with the bearings in the snout, not major but something to be aware of. Anyone have any info on this?

 

[Griff]

They spin pretty fast for a small blower and are overdriven at 2:1 stock. At 5000rpms, the blower is spinning at 10000rpms. Max recommended rpms for the blower is about 13000rpms. I was actually spinning mine right around 13k at WOT with the smaller pulley. That creates a lot of heat and is why I changed the lube often. I never had any issues. I do know that the splined shaft is NLA, so if the front bearings go, you will have to changed to the keyway shaft. I always figured that if mine went, I would just change to a 250 blower.

 

[Dude! Sweet!]

I have a pair with about 250 trouble free hours and they've have had excellent maintenance. I was told once that the stock blowers could develop some sort of issue with the bearings in the snout, not major but something to be aware of. Anyone have any info on this?

Wow! Talk about a light bulb coming on... We were getting some belt slip and squeal before I replaced my 525SC (Griff's old motor) with the big NA motor... I wonder if we were experiencing some latent bearing issues. Ah well. Water under the bridge! :sifone:

 

[glassdave]

So far I've had no issues and change the oil when i do the engines, also check for side play and anything out of the ordinary spinning them by hand. I will hafta see if i can dig out the post i saw pertaining to the snout bearings. I seem to remember there being some kinda update kit available from Weiand.

 

[Dude! Sweet!]

So far I've had no issues and change the oil when i do the engines, also check for side play and anything out of the ordinary spinning them by hand. I will hafta see if i can dig out the post i saw pertaining to the snout bearings. I seem to remember there being some kinda update kit available from Weiand.

Sold the motor 2+ years ago. Just kind of an interesting thought to me at this point. Might have been, might have been something else... I'll blame it on the driver! :cheers2:

 

[Griff]

Wow! Talk about a light bulb coming on... We were getting some belt slip and squeal before I replaced my 525SC (Griff's old motor) with the big NA motor... I wonder if we were experiencing some latent bearing issues. Ah well. Water under the bridge! :sifone:

I used to have to replace the belt about every 50 hrs or so. They were only about $35 at NAPA. It would start to slip and you could see the boost drop off a few pounds when you hit the throttle hard.

 

[Boat Tech]

I don't think your engine Will Qualify for this Engine Refresh Maintenance Program

From Mercury Racing, But just in case Here some info for anyone with a 525 EFI Race Sterndrive.

Mercury 525 Maintenance Deal.

--------------------------------------------------------------------------------

525 EFI Race Sterndrive
Engine Refresh Maintenance Program

Fond du Lac, WI-based Mercury Racing continues to offer factory engine refreshing and sealing certification for the popular 525 EFI race sterndrive engine package. The service is available to all offshore race organizations and competitors racing the 525 EFI sterndrive engine.

The factory-direct service, based at Mercury Racing’s world headquarters in Fond du Lac, Wis., features a complete inspection and refresh of the engine – from the bare cylinder block through a final power run on a dynamometer.

Refreshes are done strictly to Mercury Racing factory standards and specifications. All replacement parts are Mercury Racing specified manufacturers’ original parts. The standard 525 EFI refresh includes a complete disassembly and inspection of the engine. Replaced components include cylinder heads and gaskets, intake and exhaust valves, valve springs, retainers, valve seals, rocker arms, lifters, pistons and rings, rod bearings, main bearings, cam bearings, rod bolts, camshaft, timing chain and sprocket set, oil and fuel filters, spark plugs, impeller kit, oil pump, fuel pump, miscellaneous gaskets, seals and hardware.

525 EFI Race Standard Refresh Service Parts Kit Contents:
• (1) Set valve springs
• (1) Set retainers
• (1) Set valve seals
• (1) Set lifters
• (1) Set cylinder heads and gaskets
• (1) Oil and fuel filters
• (1) Set spark plugs
• (1) Sea pump – impeller kit
• (1) Set exhaust valves
• (1) Set intake valves
• (1) Set rocker arms
• (1) Set pistons and rings
• (1) Set rod bearings
• (1) Set main bearings
• (1) Set cam bearings
• (1) Set rod bolts
• (1) Camshaft
• (1) Timing chain and sprocket set
• (1) Serpentine belt
• (1) Oil pump and shaft
• (1) Fuel pump
• Miscellaneous gaskets, seals, hardware

Racer price for the refresh of one engine is $9,949.80. The fee covers labor and replacement of parts included in the standard refresh kit. Owners will be notified for approval prior to replacement of additional major components. All other parts required in addition to the cost of the standard refresh will be invoiced along with any additional labor.

A minimum flat fee of $1,200 per engine will be charged for engine disassembly and inspection if the owner chooses not to go forward with the engine refresh.

Owners with Mercury Racing race accounts can send their engines in direct or through a qualified Mercury Racing Total Engine Application Management (T.E.A.M.) accredited OEM boat builder or dealer.

Owners are required to contact Mercury Racing at 920-921-5330 for approval prior to sending their engines.

 

[Gordo]

The 24 Outlaw of Banker Ron / Outlaw Cowgirl has been running a 525 SC for a number of years. They don't run the boat hard- (except for "Shootout" weekend) and have always done more than exceptional maintenance, including blower service. I do not remember exact hours, but a few years ago we pulled the heads and sent them in for complete re-fresh, (new springs, valves, etc). I know we discussed replacing the belt last year, but I doubt they put more than 5 hours on the thing all summer. Knowing them, we will probably replace all belts when they pull it out this spring.

 

[OutlawCowgirl]

:iagree:belts would be a good idea this spring along with spark plugs. (smaller pulleys, smaller pulleys, smaller pulleys, she needs to go faster) :driving:This engine has been nothing but good to us. And I would think we put more than 5 hours on it, the 5 hours was the summer you decided to check out on us for a while. Remember!
We maintain her very well. This last spring I changed the oil and all the filters. We run Royal Purple in her and do not run her hard, except at the Shootout. I believe with the right care she could live forever!!! Damn good engine if you ask me!!!
We did pull the heads the fall after we dropped that engine in I think it was 04 maybe. That was a fun project! I feel blessed that I have worked on an engine right beside Gordo. He has taught me everything I know and is a damn good teacher.

 

[YoungPerformance]

Can some of you guys share rebuild recommendations for Mercury 525SC's. I dont have alot of experience with them.

The motor in question has 397 hours. Meticulous maintenance has been performed but the motor has never been gone through.

Thoughts?

At this point, at least the top end needs to be done. The bottom end is up to you at this point. It should go a little longer, but it may be easier to just go through the entire engine at once. This will prevent you from paying for some items twice. I would perform a leakdown test first to determine the overall health of the engine. This will give you a good idea if the bottom end must to be done now or if it can wait a little while longer. It really depends on how much running you do in a season. If you put 75+ hrs a season, then I would recommend doing the entire engine now. If it is only 25 or so, then it can probably go longer. I would still freshen the top end now with 400 hours. I would also have the blower looked at. They do have a tendency to fail. You must keep up on the oil changes since the oil constantly gets diluted with gas. Gasoline is a terrible lubricant and is the cause of most bearing failures.
If you are looking to upgrade for a little more power, then there are several things you can do when the engine is freshened up that won't really cost any more money. As mentioned, you should go to a hyd. roller. You can put a little larger camshaft in. To switch to a hyd roller will cost some money, but going a little larger on the cam does not. Also, instead of turning the blower much harder and taking a chance of it failing, you can increase the static compression. Not only will this increase power, but it will increase efficiency by reducing the quench area. This also won't really cost any more. You can up the power without the addition of an intercooler since you are not spinning the blower any harder. If you want to spend the money, an intercooler will certainly help. That will allow you to up the blower some and make even more power. It all depends on what you want and what your budget is.
Let me know if I can help in any way. Good luck with it.
Eddie