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502 MPI Gen V freshen w/ possible cam upgrade questions for the pros

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Old 11-04-2015, 12:57 AM
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Ah the story lol...

Ran aground which did some hull/ drive damage and sucked up debris for good measure, immediately overheated one engine and burned up its impeller. Limped back home after running out of gas twice (learned all about fuel gauge readings that day) and flushed and installed new impellor but now it had a miss. I checked plug and had water coming out of #2, I checked compression which was at 100-110 on that cylinder. Took it in to shop for hull and drive repairs and they took apart the engine to see if the overheat was caused by the original incident. They found a blown head gasket and evidence of previous water ingestion which they said was caused by OE exhaust (which I had replaced right after I bought boat with the Stainless Marine setup). They stripped the heads clean and took it down to the block to inspect the pistons, heads and all bearings. Turns out it was not covered since they said it had some signs of previous water intrusion. The head gasket was most likely on the verge of failing and the overheat sent it over the edge I'm guessing. The shop wanted 6k to replace all the valves, replace the main bearings, replace two pistons that had some scuffing and somewhat stiff wrist pins, all the rings and some light machine work to put it all back together. I felt I could get a full proper rebuild with upgrades even for way less money with a little legwork and some of my own labor so I here I am asking these silly questions... boating ugh... lol.
The blown head gasket was obviously caused by the overheat. I hope insurance is at least paying for some of the engine repair.
I don't know how the shop can definitively say that any damage was caused by "previous" water intrusion and not by the current situation.

I don't think you'll come out at under 6k if you go to full roller engines.
Upgrading the good engine to a roller cam, lifters, rockers timing set, springs, etc will cost 2-3k alone.

I think if I was in your situation, I would do one of the following:

1.Sell your good engine complete(4-5k) and look for a pair of higher hp takeout engines.
2.Have the bad engine completely rebuilt to stock.
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Old 11-04-2015, 05:52 PM
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The blown head gasket was obviously caused by the overheat. I hope insurance is at least paying for some of the engine repair.
I don't know how the shop can definitively say that any damage was caused by "previous" water intrusion and not by the current situation.

I don't think you'll come out at under 6k if you go to full roller engines.
Upgrading the good engine to a roller cam, lifters, rockers timing set, springs, etc will cost 2-3k alone.

I think if I was in your situation, I would do one of the following:

1.Sell your good engine complete(4-5k) and look for a pair of higher hp takeout engines.
2.Have the bad engine completely rebuilt to stock.


Yes I agree the head gasket let go as a result of that days events... The shop told the insurance company the cylinder walls showed signs of water discoloration on the cylinder walls. They said there was little spots/staining that had been there a while and pitting or wear on some of the valve stems from the old leaking manifolds. Insurance paid for the tear down to a certain point but that's it and the rest is on me...

The 6k they were wanting to charge was to put the engine back together in stock form but replacing the absolute bare minimum. If I add everything up on CP Performances site that I think I will need to do a full rebuild, I end up at about $3200-$3500 in parts depending on a couple variables (I'm sure I can whittle that down with some shopping and better knowledge of what I actually need lol). I can't imagine machine work being another $2500-$2800 but I have not made any calls on that part so it may be?

Option #1 is not an option due to cost but sure would be nice...
Option #2 is appealing due to the cost factor that's for sure. Probably the smartest option, but who here has been smart when it comes to boats lol...
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Old 11-04-2015, 06:22 PM
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Diamond Dave, I believe CP Performance and Hardin Marine are the same Co. Bill @ Diamond Performance (an OSO paying entity) is a great guy to deal with and is also a Hardin/CP dealer. He has everything, and more, and his pricing is either the same or in some cases lower than the CP/Hardin. I always try to support the companies that contribute to this forum. FYI
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Old 11-04-2015, 06:39 PM
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Diamond Dave, I believe CP Performance and Hardin Marine are the same Co. Bill @ Diamond Performance (an OSO paying entity) is a great guy to deal with and is also a Hardin/CP dealer. He has everything, and more, and his pricing is either the same or in some cases lower than the CP/Hardin. I always try to support the companies that contribute to this forum. FYI
Lower prices are always a good thing! If I get enough responses here to sway me in the "it's worth it to build it" direction I will hit him up for sure thanks for the info!
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Old 11-04-2015, 08:32 PM
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You never really said what the budget was/is.
If you want to know what direction to go here is a simple formula I would use to guide me:
Budget divided by 4 = money allocated for each engine rebuild (twins)
you MAY get away with divided by 3 but I bet not.
Happy calculating and do not show this formula to family members i.e. significant other.
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Old 11-04-2015, 10:36 PM
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Thats a aged 502 that has seen shallow water. I have 5bux that says there is 5 pounds of silt in the bottom of that block.probably in the other one too. Oe 502 head gaskets with raw cooling have a genetic destiny with a early fate as it is . Just make sure whatever you do someone pops the freeze plugs and makes sure the cylinders are still nice and round. Intake and ecm and 219 valves will support 500hp with specific cam for that app.and long exhaust runners cast or otherwise. Just wont look as cool as the blue. Yes you may need bob m and a roller if you are in need if idleing around with the exhaust going out the prop. Thats probably the biggest wildcard especially if you want to keep it simple
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Old 11-05-2015, 12:06 PM
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i just purchased a fresh water 502 mag boat with thru hull exhaust, it has 550 hours on it but seems to run very smooth. Diamond Dave i would love to ask a few questions about what is in my future but also don't want to high jack your thread, id rather ask permission than apologize.
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Old 11-05-2015, 01:31 PM
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Originally Posted by GLENAMY 242SS View Post
You never really said what the budget was/is.
If you want to know what direction to go here is a simple formula I would use to guide me:
Budget divided by 4 = money allocated for each engine rebuild (twins)
you MAY get away with divided by 3 but I bet not.
Happy calculating and do not show this formula to family members i.e. significant other.
I was HOPING to be somewhere around 4k if I go the full overhaul and upgrade route. Are you sure you didn't mean to multiply instead of divide in your formula? Lol

I saw this thread: http://www.offshoreonly.com/forums/d...e-results.html where all that was done to a completely stock (newer) motor was cam, springs, tune, roller rockers, exhaust and intake mods. My thought here was to rebuild using OE parts and use valve train parts from a newer roller cam motor (they may be cheaper) but upgrade only the rockers, springs and cam w/ tune as done in the thread (if this is even possible with my gen 5??) and forgo the intake mods at this point to keep costs down and do that later possibly.

IF I can reuse most of my OE components and just re-ring, new bearings, gaskets, buy just the upgrade parts (w/o intake) in the thread I'm at about $1700 in parts plus whatever machine work will cost.

Last edited by Diamond Dave; 11-06-2015 at 11:04 AM.
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Old 11-05-2015, 01:41 PM
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Thats a aged 502 that has seen shallow water. I have 5bux that says there is 5 pounds of silt in the bottom of that block.probably in the other one too. Oe 502 head gaskets with raw cooling have a genetic destiny with a early fate as it is . Just make sure whatever you do someone pops the freeze plugs and makes sure the cylinders are still nice and round. Intake and ecm and 219 valves will support 500hp with specific cam for that app.and long exhaust runners cast or otherwise. Just wont look as cool as the blue. Yes you may need bob m and a roller if you are in need if idleing around with the exhaust going out the prop. Thats probably the biggest wildcard especially if you want to keep it simple
Funny you mention that... I have had issues with my water pressure gauges. I have flushed numerous times but I'm sure there is more in the block I can't get out. I will make sure I have machine shop look into the bores being ok and round and no silt left inside it. Yes idling around quiet with the wife gabbing is important so.... or is it lol.
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Old 11-05-2015, 01:44 PM
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i just purchased a fresh water 502 mag boat with thru hull exhaust, it has 550 hours on it but seems to run very smooth. Diamond Dave i would love to ask a few questions about what is in my future but also don't want to high jack your thread, id rather ask permission than apologize.
Hey go for it! I'll share what I know with anyone that needs help! Granted I am still learning also but have blundered through a lot so far with every ones help. You can post here or PM me if you want!
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