Smoked 502 mag
 

Well, I received the bad news today that I ruined one of my engines. I was looking for some advice on what to do as far as replace, repair, re-power or rebuild. The oil pump went out on a run around the lake and all I saw was smoke and burnt oil smell. The mechanic said he would replace the whole motor. Looking for any other ideas, thanks.

the " oil pump went out " ? you need a new mechanic as well as whatever repairs...

a std 502 is a simple straight forward rebuild depending on the damage and shortblocks are available from any number of reputable outlets...

as for the mechanic, after some 30 or 40 years in the business i have never once seen an oil pump fail on its own. i have seen shafts twist off and them fill with trash and jam and crack open or any number of them get broken for a lot different EXTERNAL causes... but i have never seen one simply stop making oil pressure on its own. blaming the oil pump for this failure might suggest to me that your " mechanic" needs to head back to trade school and not be the guy you want doing this work.

I just rebuilt my motor last year and for what I paid someone else to do in machining and dis-assembly/assembly I should have bought a Dart short block and done the rest myself. I could have had a lot more motor for the same price. Just something to think about, I don't want you to have the same regrets I have. I would check out the motor more carefully though it may not be as bad as he said.

I would pull apart your engine...see what you have...sometimes rebuilding what you have is better than buying some of the new "junk" for sale out there...

Just learning this stuff myself but from a practical standpoint you are kinda limited as far as I can tell. Since you have twins you really need to keep the motors the same or upgrade both at the same time. If you have the coin have some fun - but if you are looking for an economical solution and you can wrench - breaking the motor down and taking it to a local reputable machins shop may be your best bet. If you need parts you can shop for those on your own. I have searched for hours on reman engines and it is really hard finding a seller that has a great reputation for rebuilding the motors. I would also consider putting somethin up in the wanted section on here to see if someone has something available for you.

this, unfortunately is terrible advice . i presume he has a boat to go boating. just like he has a car to use for transportaion or a computer to look at porn. a very very smart man once taught me " do what you do best and pay other people to do what they do best. he doesn't try to fix his own street car or computer... with any luck he is smart enough to know not to try to build his own motor.

if he was a professional in the engine building business, then , aside from the fact that he wouldn't be posting this question here, he would also have the skill set to fix it. clearly neither of those things is true. he has very basic and straight forward hardware. if he is smart he forgets and completely ignores the " do it yourself and then fix it 5 times again later routine and just buys a professionally built short block ( they are cheap) has his heads freshend by a local skilled professional and get back on the water. if he does that he will spend less money than doing it himself AND not have to throw it away 3 times in the meantime.

if he wanted to learn how to build v-8's there were easier and cheaper ways to do it than buying a boat and blowing it up.

and please none of this nonsense about " i paid a guy and it blew up anyway".. in those cases you paid the wrong guy... just like the wrong guy screwed up your street car and your brother in law killed your computer trying to fix it. the only person that can keep you from being stupid is you.

Steve, do a quick Google search out there for "Mellings oil pump failure" and you will find a lot of car racers having issues with failures of the M55 series pumps due to a design change with a thinner casting. Now the M55 was usually a small block pump, but it would also fit a big block (I think), and Mellings also made some of the Moroso pumps. That being said, it sounds more likely that he lost a pickup or something else like that.

I am dealing with an oil pump issue of some type with a 1078 pump on my engine, but I have not opened the engine up yet to see what happened. I will agree with you that it is pretty uncommon to see a Chevy oil pump fail on its own.

It is OK to have a different point of view but calling someone you don't know stupid is just idiotic. I changed a set of brakes when I was a teen - had to do it once for the first time. Changed dozens iof brakes since then. In my 30 years or so since that first brake job I have done all kinds of wrenching on autos. When I bought my first boat it had outboards and as a used boat they had problems - did the wrenching myself and saved a bundle. Nothing failed because of my work. Have my frst boat with I/O's now. Having an overheating problem - pulled the manifolds, risers and heads all by my itty bitty self. Never did it before but I can assure you the boat is not going to self destruct because it is my first time. So if you feel inept about working on motors then pay someone. But you really are in no position to speak for everyone else. If the OP doesn't feel comfortable and has the money to pay for the work to be done - then he can say so.

BTW - you offered absolutely no advice for the OP - your post is useless. No information about how much it may costs for a rebuild or for a long block. Who is rebutable in doing them, etc.

Sorry OP for the negativity - I just get pissed when someone attacks for no reason and offers nothing worthy as part of the negativity.

To the OP - I had a piston go south on my 454 a couple of summers ago and started hunting around for a replacement long block. A buddy of mine had decent luck with 1-800-runs-new, and bought a complete new GM 502 mag from them with a 1-year warranty for less than $6k. However, that was ten years ago, and since then it seems the price on these engines has gone up considerably. When I priced them two years ago they were over $7k for a GM base engine, and some were saying that they were no longer warrantying the mag engines in marine applications (which I find ludicrous - never did verify that.) If you buy one straight from Merc, you are likely to be well over $10K for a 502 Mag. I think GM still has the crate 502's available from many of the dealers, but most of them explicitly state not for marine use, and once again you may have warranty issues. It might be worth it to try to find a competent MARINE engine rebuilder and have them tear it down and inspect it. If you are lucky it might be an easy and relatively inexpensive rebuild, but as with anything, get any warranty agreement in writing. If it was an oil pump failure and it was run at speed when it let go, you may very well be looking at considerable damage, not only to the reciprocating assembly, but also the block and heads.

useless? really ? do a quick search here... probably 2000 plus threads from people with no experience or skills throwing away their money doing badly what they do not know how to do at all. what IS stupid is encouraging someone to tread that same path and consider it good advice.

i answered his question directly and correctly. buy a shortblock from a professional and have another professional put it together and write the check. that is the limit of his mechanical skill set and if you fail to recognize that, well ... that speaks for itself.

what YOU did at 16 and what YOU do now is not relevant in any respect. what HIS smart play right now is the question and that answer is self evident.