525SC questions....
 

I've been told these 525SC engines should have the valve springs replaced at around 400 hrs., is this true?

If so can somebody recommend what springs to use; maybe a good aftermarket replacement?

I have both engines out to take care of a couple of anoying minor oil leaks so if I should be replacing the springs I'll do them now.

Since they are out, you should really do complete top end refreshes. Valve jobs, head gaskets and valve springs.
The stock cam is a Crane 132561 and pretty sure the stock springs were Crane 99839-16.

I'd go ahead and swap the cams over to rollers while you have the motors out.

That would be a nice upgrade. However, probably looking at 800-900 per engine to convert to a hyd roller.

IMO, that 1600-1800, would be best spent on getting some slightly larger blowers, like a 250-256 blower. Run 6-7psi and they will wake up big time. Blower shop 250 would be really nice.

IF the blowers havent been rebuilt, and have 400 hours, i'd get them gone thru now.

It will cost at least $1200 more per engine to change to roller cams.
Having the blowers gone through is good idea.

Thise are pretty mild cams. If you weren't already taking the engines out, I would say to not worry about the springs yet. Since they are coming out and you're putting fresh gaskets and such on, go ahead and put new springs. If you were planning on pulling the heads off, go ahead and bore notch the cylinders and lap the valves. Costs no extra money, just a few hours of your time.

MC

I really don't want to tear into the engines too much, they both run perfect and the compression checked out very good as well as a cyl. leak down test. The previous owner was very good on his maintenence, they've seen a pretty easy life so far. My plans are to go through both of them next winter and do some upgrades; roller cams, better rods, etc. but right now I'm limited on the budget since I just bought the boat this past Sept. and still need to buy a bigger lift and some dock modifications.
The blowers look like they have been apart before, they showed no signs of fuel in either of the gear cases.

The stock rods arent bad. Unless your going all out with lots of boost and gonna try to make 800HP, the stock rods are fine with good bolts.

Roller cams are a nice upgrade. you will be limited to about 575-600HP with the stock blower. Bigger blowers, like a 871, its not that hard to make 700+ out of the 454 blocks.

I am in rebuilt now of mine, I have swap the rod for Callies Compstar H Beam, .030 oversize with block valve notch, Speed Pro forged piston, new aluminum Hedelbrock Performer RPM head 45 cfm more than the stock head, Crane costom grind 114lsa with less overlap 67 deg than the stock one 74 deg to keep the boost in the cylinder, estimate comp ratio at 7.5:1 - 7.6:1.

I will possibly get a porting job on the head for an extra 30 cfm or so.

I estimate at least 650HP possibly 700hp if i am lucky.

I think i will be able to keep the boost at 5.5 with the stock pulley due to less overlap on the cam and smaller intake runner 315cc instead the 325 or 335 stock.

The stock cam is very not good for this surpercharger setup.

I keep the comp ratio low for a bigger blower in future and boost arond 7 with a 250 or 671 blower.

If your going to the aluminum head, I'd get the compression up. The stock 7.5 or so to one is pretty dismal. 8.5:1 with the aluminum heads is good.

Sounds like your on the right track, but no way 700HP with the stock blower and 7.5:1.

I can tell you this. I ran 460CI, dart race series alum heads, mild port work, 308cc intake runners, hyd roller 236/245 114LSA, compression was about 8.3:1. With the 177 blower, I was turning the blower at 2:15:1 overdriven. Making about 4.5-5psi. I then went to a 250 blower, drove it at 1.68:1 overdriven, gave me 5psi. 1.8:1 gave me 7psi.

On my engines, if i wanted 7psi, I probably would have had to drive the small 177 to 2.3:1. Turning the engines to 5500RPM, thats almost 13000 rpm blower speed. Talk about a heat pump. The bearings probably wouldnt last long, and the added boost would really do nothing for power.

The more cam, better flowing heads, will drop the boost psi. Once you start getting into that stuff, you outgrow the small blower quickly.

To get near 700HP, I'd say 250/256 blower, up the compression, 7-8psi with a chiller. Im currently rebuilding mine, H-beam rods, JE pistons, and adding 8-71s. If i get 700-725HP at 5500-5700rpm I'll be happy.

Do you have full spec or the parts no of your cam?

288/298 .629/.632

intake opens 8.0* btdc
intake closes 48* abdc
exhaust opens 61 bbdc
closes 5* atdc

114lsa

its a custom hyd roller cam for a supercharged 454

The one i am locking

@.050

intake open 6 btdc

intake close 44 abdc

exhaust open 57 bbdc

exhaust close 1 btdc

230/236 duration

109/119 max lift

114 lsa

This a Crane Cam recomandation i dont know if i can find better for now with my setup (177 blower)

Like was already said, more than 600hp with the stock 177 blower, stock boost and comp ratio is not gonna happen.

I think with the right cam for this litle 177 is posible to get 650hp not sure with the stock or with smaller pulley i have one with 2.85 dia, i know that my comp ratio is low for aluminum head but i think the benefit of higner boost is better than puting up the comp ratio, i know this litle blower make more heat than a biger one but for this year i will try it, the bigger blower is in project for future.

The only reason i want to keep the CR low is for the benefit of the higner boost (around 7 with no intercooler) of the future larger blower.

7lbs of boost with a aluminum head is not a problem at 8.5:1, using the right blower. Add a chiller and get even more. Aluminum heads are superior in that they dissapate the heat so much better than cast iron.

You are actually better off running a bit higher static compression with a small blower. You wont have to drive it so hard to make decent boost.

If your running the 7" drive pulley, with a 2.85" upper, thats 2.45:1 blower ratio. If your propped for 5500RPM, , thats 13,500 blower rpm. I believe weiand stated no more than 13000 rpm with those blowers, and thats mainly on the street. 13500rpm for sustained wot runs in a boat, i'd be nervous about it.

I have email Weiand about 177 marine max rpm he have tell me no more 14000 rpm I know this is very fast at between 13000-13500 rpm. I dont drive at wot long time mostly cruise at 3500- 4000 engine rpm

as far as for cams, contact Bob @ marine kinetics in the process of helping do a pair of 98 525SC's right..can't believe merc in the infinate wisdom went with flat tappet cams even as late as 98...Bob doing up new cams and valve train as we speak...he is the man to talk to on cams/valve train !!

What is the dia. of the stock pulley for these blowers?

I'm pretty sure mine have not been changed but just want to be sure.

They are set up at a 2:1 overdriven. Pretty sure the stock top is 3.5" and the lower is 7".

7.5? Get some turbos or a centrifugal supercharger and blow 20psi on those babies.

That will last about 5 minutes in a boat. :whistle:

Now it is time to chose between keep comp ratio at 7.5:1 or put it at 8.5:1 and keep the 177 turn at 2:1. But do you think with a 250 blower with cr at 8.5:1 and 7lb boost on 91 octane will be ok with no chiller ?
I want to built it for a future bigger blower like a 250 or 671...

I am looking for a msd ingnition box which is the best? What's about the programable ing curve box?

Also where do you suggest to set the timing advance ?

Thanks for the help!

stock blower pulleys?
 

Anybody happen to have 1 or 2 of the stock upper pulleys for the 177 blower used on the 525sc engines?
There not the same as the street versions of this blower; different splines.
I need at least 1.....

The 250 Blower at 7lbs, with aluminum heads, will be ok. I did it. Just be up on your a/f ratio and timing. It will run strong. Timing 30-32* max.

I would definitly get the compression up to .75-1.0 point from where you are now.

The 177 to 250 blower is a nice upgrade. I did that. Now I am installing 420 blowers, in the hopes of gaining a little more. But its all in how much power you wanna make. I would say the 250 is good for up to 650HP or so on a 454CI. 177 about 600. In general.

I have a similar blower set up. I'm switching to MSD programable this year. The programable will let you run a complex curve based on many factors including weight of the boat etc... Unlike a boost retard this will allow you to run more inital timing. The timing adjustments may provide more farvorale EGT temps while cruising or in non boost conditons, and a sweet spot for starting and idle conditions. And if all this makes no difference I can still watch porn on the laptop

Save your cash and lock the timing. Better idle, worked flawless for me! My single dominator on the 250 blower and a nice cam, would not idle I. Gear without puking with 12* initial and 18* advance. Locked it at 30 and went boating

I have a 2.75 old style splined off a 250B&M. Think it takes the same pully as the 177.

can you send me some pics?
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Timing at 30-32* with the stock merc 525sc ing???

If i keep the stock ing and set at 32* my initial timing will drop at 10*

The oem timing spec is 35* at 4500rpm and 13* initial timing total module advance 22*

I run 30* all in timing. 177s, 9.5:1 compression w/ alum heads and 6psi. I have 2 - 3.0" original splined merc blower pulleys if anyone want to buy them.

pic sent

I'm interested in a 3.625 pulley if anyone has one.

[email protected]

That is larger than a stock pulley and I don't think anyone ever made any that were larger.

My mistake, I was thinking the 177 & 250 pulleys were interchangeable. According to The Blower Shop the 250 is 16 rib & the 177 is 10 rib or keyed. That being said I have an old style (1.75” recessed) 16rib 2.75 for a 250 & need an old style 3.625 if anyone is interested or has one.

Convert over to the automotive keyed shaft and your pulley is a phone call to jegs or summit away. My opinion about what timing to run is this...My motor was run with retarded timing like around 30 total, and at about 140 hours (cant remember the exact meter reading) the exhaust valves were leaking badly. Retarded timing elevated the exhaust temps and ruined the valves. The Merc curve works very well and even though it has 35 deg total, its stepped and is not all in until 4500. Do not try to reinvent the wheel here.

177 was a weiand blower. 250 was a B&M. Different pulleys.

[QUOTE=Old Navy;3608633]Convert over to the automotive keyed shaft and your pulley is a phone call to jegs or summit away. My opinion about what timing to run is this...My motor was run with retarded timing like around 30 total, and at about 140 hours (cant remember the exact meter reading) the exhaust valves were leaking badly. Retarded timing elevated the exhaust temps and ruined the valves. The Merc curve works very well and even though it has 35 deg total, its stepped and is not all in until 4500. Do not try to reinvent the wheel here.[/QUOTE




How difficult is it to change to the keyed shafts?
Is it basicly a "bolt on" swap or does it involve disassembling the gear cases and rotors?

[QUOTE=JD33;3609129]
Pretty easy, no need to disassembling the gear casse or rotor, just disassemble the snout and swap the shaft to the keyed shaft. In case if you need to change the shaft coupler on the gear just disassemble the front cover.

Thats what it looked like from the pics I've found on the net, but sometimes looks can be deceiving. LOL

This may be the route I have to go, so far no stock dia. pulley with the correct offset located to fit my splined shafts.

[QUOTE=supermx96;3609138]Thats what I did. I think the new shaft came with a new coupler so I changed that too. Thats what you should do JD33 instead of messing with changing to my spined shafts/pulleys which may not work anyway.

I'm curious though if anyone knows what snout lengths merc used on thier 525sc? Its seems my splined blower pulleys are odd and never fit the merc splined shafts people have.