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Advice on re-power options

Old 02-01-2017, 07:28 PM
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Originally Posted by Unlimited jd
Do not buy from whites. A friend has 2 piles of **** from them that didn't last 10 hours. The merc 540 leaves a lot to be desired. There a ways off from what the original description pre intro to the market was.
your friend from cape cod?if not,,there are 2 piles down there too.
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Old 02-01-2017, 07:33 PM
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Originally Posted by Unlimited jd
I'll find out, the 540 was originally supposed to make more power and be a little cheaper than what it came out at. I want to say it's all done by 4400 rpm?
Sounds like it. Merc site says WOT 4200-4600 RPM. Torque is good, 560 @3500. I'm sure i'll want to go faster before long, which will mean throwing more money at it. Well you all know that story.
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Old 02-01-2017, 07:37 PM
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Originally Posted by sutphen 30
your friend from cape cod?if not,,there are 2 piles down there too.
Yep, I'm sure you're talking about lee in Truro
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Old 02-01-2017, 09:17 PM
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i may have a pair of low hour 525 efi's for sale
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Old 02-01-2017, 09:27 PM
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Originally Posted by billy boats
i may have a pair of low hour 525 efi's for sale
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Old 02-01-2017, 10:15 PM
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Originally Posted by billy boats
i may have a pair of low hour 525 efi's for sale
We repowered in 10 with a set of takeout 525efis with 10hours. Nearing 500 now with only 1 sea/fuel pump failure. Most of the time it's 4K rpm cruises. Best power in that HP range I've ever seen
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Old 02-01-2017, 11:06 PM
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Definitely a big decision to make, especially if you want "turn key reliable power".

Whats your budget?

What type of boating do you do?

Saltwater?

How many hours are on your 525sc's?

What is wrong with your current engines?

What parts are salvageable?

Power and speed goals?

Cost of the Mercury 540 repower?

My advice so far, best to assume all used engines need to be "freshened" by your own mechanic, so budget accordingly and you can be VERY satisfied with some nice used take outs.

Start a thread in the tech section "recipes for budget built 550hp" and let the power of OSO design you a rebuild utilizing whatever parts are salvageable on your engines. You might be surprised how many deals there are out there, like Engine Quest heads, or modifying ZZ502 crate engines.
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Old 02-02-2017, 12:18 AM
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>>>>Whats your budget?
Well It started out lower thinking i was going to just do a refresh/rebuild, but since Dave doesnt recommend it and we've been looking at the merc 540 remans, it has ballooned to up to 30k for motors and another 10k for installation and while we're at its... new gimbals, steering cables, any drive issues, etc.

>>>>What type of boating do you do?
I live up the Patuxent River about 30 miles from the Chesapeake. Take her out every weekend during the season, mostly river running down to the mouth of the river where we hang out, do a lot of beaching, sleep out on the boat and come back at the end of the weekend.

>>>>Saltwater?
She'll get a bit of salt in the bay but by the time i get back home its less than 1 part per thousand, and then she get flushed every time.

>>>>How many hours are on your 525sc's?
Ive just been piecing this together from my dad's logbook. Some history: My dad's not with us anymore. He got the boat back in 93, converted to bravos in 99, had Dave build the 525 SC clones from a pair of new 454/420's he had sitting around in 2001. I had thought it had 350 hours but with info in his logbook i now believe these motors are just under 300 hours (the discrepancy has to do with when he put new meters in after redoing the dash). So not too many hours, but they've been running 15 years.

>>>>What is wrong with your current engines?
Stbd motor was a bit down on power at the very end of the season, and i noticed some emulsified oil in the dipstick and under valve covers. Compression test showed #8 cylinder not holding pressure (I drained the oil which had no water in it, so now not sure if the two were related). Hauled boat over to MDG, Dave took manifolds off and pressurized the cylinder, said he couldn't hear air coming out of the top so he's convinced its a wrecked cylinder, eg probably badly scored. Motor runs and sounds fine. He doesnt recommend rebuilding as its been running for so long and blocks aren't worth rebuilding from.
Port motor has no apparent issues. Also to note: earlier last summer my Stbd supercharger stripped out its splines. I pulled it and sent over to Dyers blowers who did a complete rebuild, was planning to do the port one this winter.

>>>>What parts are salvageable?
We haven't opened them up and we haven't discussed exactly which parts would be reused in case of a rebuild using new blocks. Dave said forget it, I'm better off selling what i've got and starting fresh. He threw out some likely ballpark figures for him to rebuild with what i've got and indeed it didn't sound worthwhile.

>>>>Power and speed goals?
Well like everyone else eventually i'd like to go faster, but aside from limitations of my current budget for motors is the reality of running bravo 1's which still shift great and have had no problems, but they are even older than the motors, having been converted from TRS in 99. I plan to have Dave pull em and check everything while we're at it, plus i do mostly flat water boating and am fairly gentle, never hole shot, etc, but still. Also worth noting: I don't have hydraulic steering.

I suppose short answer: i sure dont want to go SLOWER than before haha. But If its possible to power up slightly, then address drives and steering in a next step that sounds appealing.

>>>>>Cost of the Mercury 540 reposer?
15k a side, complete including exhaust


>>>>>My advice so far, best to assume all used engines need to be "freshened" by your own mechanic, so budget accordingly and you can be VERY satisfied with some nice used take outs.

Sounds like good advice.

>>>>>Start a thread in the tech section "recipes for budget built 550hp" and let the power of OSO design you a rebuild utilizing whatever parts are salvageable on your engines. You might be surprised how many deals there are out there, like Engine Quest heads, or modifying ZZ502 crate engines.
The issue here is that i dont have the skills to manage my own budget build, and Dave understandably doesnt have the time or interest in that kind of thing he just wants to do the job right one way or the other... I pay him to rebuild them, or buy something and he does the install. Im also limited in that the boat sits on a lift at the house, but i dont have a trailer as no tow vehicle and couldn't even get a trailer into my driveway which has some tight bends in it. So i dont have the option of parking it at home and taking my time sorting things.

Merc 540 remanufacters seem like the safest bet: "new" with warranty, drop right in and go, lower power so no additional drive worries. But eventually I'm gonna get tired of getting passed by CC's and fast pontoons, then I'm gonna have to throw more money into hot rodding em.

If i can find decent 525's in my price range that might be an option, but as you said I need to budget for freshening, plus i guess new exhaust. The stainless marine manifolds i currently have are as old as the motors, if they were pressure tested would you consider it safe to run em a couple years and change em out later? Or is that just not worth the risk?

I also see Ron Sporl is selling a pair of completely rebuilt 525SC's with all new components carb to pan for 35k. Apparently dynoed at 700, the extra power sounds appealing but how much should i worry about the bravos and lack of hydraulic steering? Though I suppose we could throw on bigger pulleys until i can redo drives...

Last edited by blown; 02-02-2017 at 03:09 PM.
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Old 02-02-2017, 01:02 PM
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Those merc 540s your talking about looks like 502 cores with a stroker crank kit and late style accessories. Still running the gm crate cam. spending 30k and saying goodbye to a good 100hp that isnt coming back until the motors come back out for cams and oil pans may not give you the warm fuzzy feeling .
A couple of zz502s and 2 sets of headers and oil pans (if your current set up is gen4) should be in the low 20ks and be close to what you had . And lighter . Maybe not faster . But will sound real nice at idle anyway.
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Old 02-02-2017, 07:15 PM
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I'm not so sure I'd be condeming your current engines to the graveyard already. They've served you well for the past 15 years, and 300ish hours, is certainly not a level of making them ready for the trash bin. AND, they have not even been torn down to evaluate exactly what the issue is, and already you're builder has you buying new power?

At 300 hours, for all you know, they might need a fresh hone job, some rings, bearings, etc. If they were truly "NEW" mercury 454 420hp engines, they should have been standard 4.250 bore size. There should be room for an overbore, even IF, a cylinder was hurt. Or, be sleeved.

Those 454 / 420 engines, had decent parts in them. Certainly capable of supporting the power you are at. A fresh rebuild on the shortblock, some new EQ iron heads, and a blower upgrade, and I don't see any reason, you can't make 600, 650, 700+HP, without getting into them being radical time bombs.

Even IF, the block was trashed, you can find those blocks for a song these days, few hundred bucks. I just saw a guy out your way the other day selling a STD bore 4 bolt main 454 block, for around 500 bucks.

Before I'd hit the big red panic button, I'd want to see exactly what the problem is , and what it will take to fix it. There's nothing exotic in those engines, that should be costing a million bucks to refresh/rebuild them.
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