525SC Catastrophic test run. Seeking rebuild advice.
04-27-2020, 07:46 PM
#21
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I'd be more curious to see what the pistons and head gaskets and spark plugs looked like.
The biggest issue with salt and the 525SC is the water ports on the intake manifold where they mate with the heads.
My engine was a 1996 with about 340 hrs on it and I'd had for a 140hrs in fresh water only HELP!!! Need Merc 525SC Intake
The biggest issue with salt and the 525SC is the water ports on the intake manifold where they mate with the heads.
My engine was a 1996 with about 340 hrs on it and I'd had for a 140hrs in fresh water only HELP!!! Need Merc 525SC Intake
If I could run the motor raw and just change the intake every few years it would almost be worth it. The whole heat exchanger thing is a pain.
04-27-2020, 07:47 PM
#22
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I have a cigarette bullet that was running 454mags, 8.8:1 compression with 990 heads. I installed a pair of weiand 177's, swapped to a blower grind flat tappet cam, and pro magnum roller rockers and a V6 ignition module on 93 octane. Dynoed at 575hp and boat picked up 10-15 mph.
04-28-2020, 12:44 AM
#23
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I sold the boat with when it had about 475 hrs and never had any issues with the welds. The intake was never pulled off again by me or the next owner who maybe put another 50 hrs on it before replacing it with bigger power. I believe when I was looking way back when I posted that thread the Weiand intake was going to have issues with the stock Tstat housing hitting the blower snout.
04-29-2020, 09:29 AM
#24
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I believe my motor has a 160 degree thermostat, when I was out cruising for the 15 minutes my motor lasted it was bouncing between 160-180. Maybe put in a 140 t stat then?
Also, ive read on a few forums that these motors should be at 35 degrees timing at full advance. Any performance loss running 30? ( I would rather be reliable anyways )
Do you have an opinion on bumping compression to 8.5:1 since I am buying pistons anyways?
Thx
Also, ive read on a few forums that these motors should be at 35 degrees timing at full advance. Any performance loss running 30? ( I would rather be reliable anyways )
Do you have an opinion on bumping compression to 8.5:1 since I am buying pistons anyways?
Thx
BT
05-01-2020, 10:18 PM
#25
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I run 177s (525sc take offs w/ dominators) with 741 cams and closed cooling. I run approx 9.3:1 compression with aluminum heads. I run a v-6 module with 31* timing all in. With closed cooling I run no tstats and runs 150* cruise and will go 180f wot. 6lbs boost or just under and wot rpm around 5500rpm. I would definitely bump compression to 8.5:1 if you go with the 731 cam. You might want to locate a dynamic compression calculator and play with that to see how your combo stacks up with the cam you choose. 8.5:1 dcr is the max and lower is safer. Note that static is different than dynamic compression and dynamic compression is what you really want to nail down. Also since its apart put some effort towards making sure your quench is in the .040" range. No lower but not more than about .050" either.
BT
BT
What size heat exchanger do you have? Mine is 4" diameter and about 24" long. I guess the point of running no T-stat over a 140 is increased flow?
Just heard back from the machine shop today and the block is getting bored 0.30 over and I will need new pistons, any recommendations on brand?
Also, if I end up buying the 731 cam, will the stock 525SC valve springs be good enough for the cam or will I need springs along with hyd lifters? I wasn't going to touch the cam but people seem to love the 731...
Thanks again for info
05-02-2020, 01:29 AM
#27
Charter Member # 55
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You should be replacing valve springs no matter if you keep your stock cam or go to 731.
I'd use these JE pistons 139477
Will give you an 8.2:1 Comp Ratio. https://www.jepistons.com/applicatio...-open-chamber/
I'd use these JE pistons 139477
Will give you an 8.2:1 Comp Ratio. https://www.jepistons.com/applicatio...-open-chamber/
05-02-2020, 11:49 AM
#28
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You should be replacing valve springs no matter if you keep your stock cam or go to 731.
I'd use these JE pistons 139477
Will give you an 8.2:1 Comp Ratio. https://www.jepistons.com/applicatio...-open-chamber/
I'd use these JE pistons 139477
Will give you an 8.2:1 Comp Ratio. https://www.jepistons.com/applicatio...-open-chamber/
05-02-2020, 12:27 PM
#29
Charter Member # 55
Charter Member
If it had new springs and you stay with the stock cam then have your builder double check the spring pressures or For the $83 for new ones, just replace.
These are the stock springs https://www.summitracing.com/search/...yword=99839-16
These are the stock springs https://www.summitracing.com/search/...yword=99839-16
05-02-2020, 12:30 PM
#30
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If it had new springs and you stay with the stock cam then have your builder double check the spring pressures.
These are the stock springs https://www.summitracing.com/search/...yword=99839-16
These are the stock springs https://www.summitracing.com/search/...yword=99839-16
I keep hearing that it wakes these things up!
I just bought a 28P bravo 1 prop so I need to spin that thing
