502 mag mpi life
12-22-2005 | 07:52 AM
#1
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From: sint maarten
502 mag mpi life
now i know there is no real answer to this question it being completely dependent on maintainance and level of abuse... BUT all things being equal... nominal oil changes, good temps , beat the bejesus out of it maybe 20 % of the time and just run it reasonably hard another 40 and the rest is just cruising around, what would a reasonable life/hour expectation be for stock mercruiser 502 mag mpi 's ?
12-22-2005 | 08:29 AM
#4
Rob
Joined: Aug 2001
Posts: 21,637
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From: Ms
Re: 502 mag mpi life
A buddy of mine has a 97 29 Scarab that would only do 60-62 so he was WFO 100%.Ive been on poker runs him jumping waves and never lifting.So it been at the rev limiter more than idel. He tortured it. At 400 hours the exhust rotted off .To show ya how he is the motor was greasy like a car motor 
I did a thread in this tech section if you do a search on it . The motor looked good on the inside .Bearring etcs Nothing was wrong with it . I made him put ARP rod bolts ,and good valve springs because of they way he runs it . We did some good machine work,rings ,bearings and eddies exhaust.
I think he had about another 200 on it now.
there tuff
Rob
I did a thread in this tech section if you do a search on it . The motor looked good on the inside .Bearring etcs Nothing was wrong with it . I made him put ARP rod bolts ,and good valve springs because of they way he runs it . We did some good machine work,rings ,bearings and eddies exhaust.I think he had about another 200 on it now.
there tuff
Rob
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12-22-2005 | 09:18 AM
#5
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Joined: Oct 2002
Posts: 5,246
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From: Ivoryton, CT
Re: 502 mag mpi life
500hrs give or take... 
I bought my 1997 502MagMPI used from a fellow that had it in a 29' Fountain so it had a tough life.
The engine had 508 hours and was no longer holding good oil pressure.
I did a basic overhaul: rings, bearings, oil pump, lifters and valve job with new springs.
She's now running great! and my boat goes 10mph faster than with a 310/7.4mpi!
Not bad for a little under $2500 invested.
The stock cast exhaust has to go. I ran Stainless Marine on my 7.4 and transfered it to my 502.
I plan to run it for another year and then turn it into a HP500EFI. I bought the cam and some other 500EFI goodies from Strip...
I bought my 1997 502MagMPI used from a fellow that had it in a 29' Fountain so it had a tough life.
The engine had 508 hours and was no longer holding good oil pressure.
I did a basic overhaul: rings, bearings, oil pump, lifters and valve job with new springs.
She's now running great! and my boat goes 10mph faster than with a 310/7.4mpi!
Not bad for a little under $2500 invested.
The stock cast exhaust has to go. I ran Stainless Marine on my 7.4 and transfered it to my 502.
I plan to run it for another year and then turn it into a HP500EFI. I bought the cam and some other 500EFI goodies from Strip...
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Patrick
Patrick
Last edited by Pat McPherson; 12-22-2005 at 09:22 AM.
12-24-2005 | 07:27 AM
#7
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Posts: 25,191
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From: Deland, Florida
Re: 502 mag mpi life
A freind of mine has 502's in a 38 Fountain. He runs the piss out of it. He told me all he did was change exhaust and keep clean oil in it. Last time I talked to him, he had over 600 hrs on it. I did hear he finally blew one up last summer. Great engines.
