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1998 502 update options. What would you do?

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1998 502 update options. What would you do?

Old 04-27-2020, 09:39 AM
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Small blower
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Old 04-27-2020, 08:04 PM
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So... are you guys saying don't bother doing any modifications at all? Or just wait until next year?

Pretty sure I know the answer, but want to verify.

Thanks for the suggestions, I really do appreciate it.
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Old 04-27-2020, 08:35 PM
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Just an opinion, don't waste the money on a carb or aftermarket efi until you tear it down for a rebuild. I doubt you will see any kind of performance gain from either.
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Old 04-27-2020, 11:38 PM
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Dont do ANYTHING to the motor this year or next year or the next except have the injectors serviced. Ditch the captains call . Make sure the there are exhaust flappers on the outside of the exhaust and also flappers on the inside of the exhaust. The flappers are VERY IMPORTANT. If you lift up the external flappers and shine a light through the thru hull exhaust you should see a metal or rubber flapper. Probably rubber. Its a butterfly type. If you just see a metal rod in there it has burned out. MUST BE REPLACED.
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Old 04-28-2020, 05:51 AM
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My have been burned out for 20 years. Depends if you get waves up the pipes.
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Old 04-28-2020, 07:26 AM
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Originally Posted by Pismo10 View Post
My have been burned out for 20 years. Depends if you get waves up the pipes.
Very dependent on the boat and how it was used. Some boats just seem to burn them out and others dont. Also depends how much time the boat was run with the captains call in the open position. The larger the swim platform the worse it is. Water gets trapped under it when launching the boat and gets in the exhaust. Also if in ocean or gulf and parked on island or sandbar the lapping of the waves can get in as it gets trapped under the platform. Tubular platforms dont count as water does not get trapped.

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Old 04-28-2020, 08:27 AM
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A 502 mag/mpi can go 700+ hours without major work. I would do the injectors as recommended above. I believe the MPI had flat tappet cam for a couple years which you would want to make sure you run the proper oil.
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Old 04-28-2020, 05:40 PM
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Thanks guys.

Not what I wanted to hear, but prob what I needed to hear.

Just talked to BUP and will be moving forward with the injector service.
Now I need to get a list of all the gaskets/O rings needed to access the injectors.

***Hint:*** anyone doing injector service might want to put together an O ring/gasket set for injector installation.

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Old 04-28-2020, 06:02 PM
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I reused the intake seals after clean and flow without issue. My injectors came back with new O rings for rail installed and new basket screens. Get some glycerin (KY jelly) to use to reinstall injectors back into the rail. The complete seal kit is 25-805511A1 and BAM sells for 18.09 each

https://www.mercruiserparts.com/805511a1-sealing-kit

Last edited by AllDodge; 04-28-2020 at 06:52 PM.
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Old 04-28-2020, 06:37 PM
  #20  
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Donít have part # off hand, felpro has a gasket set (4 runner gaskets) for upper plenum.Mercruiser 805522A1

Last edited by SB; 04-28-2020 at 06:45 PM.
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