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Convert a 502 Inboard motor to use with a Sterndrive

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Convert a 502 Inboard motor to use with a Sterndrive

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Old 08-09-2018, 06:56 PM
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Default Convert a 502 Inboard motor to use with a Sterndrive

Hey everyone I'm new to this forum but have used it many times in the past. Lots of great info on here.

I have tried searching for the answer to my question but haven't be able to find a clear answer. So I thought I would make an account and make my first post.

Currently I have a 454 attached to a Bravo drive. I looking at swapping out the 454 for a 502. From what I have read a sterndrive 502 will swap in pretty straight forward.

Now I have come across a 502 that was from an inboard boat If I remove the transmission and put on my 454 engine coupler will that motor be ready to be used as a stern drive with my bravo? I know I might need to modify the fuel system if the 502 doesn't have a mechanical fuel pump.
But I have read somewhere that the starter location is different based on weather its and inboard or sterndrive. Is that true? Does it matter when its used as an sterndrive?

Just to clear any confusion. I'm not trying to convert a boat from an inboard to a stern drive. I am trying to use an inboard motor in my sterndrive boat.

I appreciate any info that can be given.
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Old 08-09-2018, 07:35 PM
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Yes should work fine but most likely your inboard has the starter on top on the rear of the flywheel housing. So you will need a block mounted starter just like your 454 and you will have to move the ring gear to the front of the flywheel.
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Old 08-09-2018, 11:13 PM
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what manu for the 502 and what ECM ? possible might have to turn off general warning 2 fault in the ECM inwhich is trans temp overheat ??

Also you will not have a drive reservoir low alarm installing 502 inboard in a sterndrive app. That discrete switch ( low drive fluid ) will not be turned on for an alarm within the ECM. No big deal with that but the trans overheat temp switch might be something to look into. Again using the word possible for trans temp ?.

I take it both engines are EFI / MPI you are talking about here ? Or maybe I missed that ? Your 454 is Mercruiser correct ? I see Bravo drive mentioned but that does not mean its attached to a stock Merc 454 ?
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Old 08-10-2018, 12:42 AM
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Yea the 502 inboard is a top mount starter.
So I can swap my 454 starter over and should I just swap the 454 flywheel or move the ring gear on the 502? Never moved a ring gear so not sure what that is like.

The 454 is a Mercruiser with a Carb. The 502 is also Carb so no need to worry about all the EFI electronics.

Thank You for the quick responses!
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Old 08-10-2018, 07:47 AM
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What rotation is the 502?
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Old 08-10-2018, 09:33 AM
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I would not change flywheels. I kind of remember the balance being different.

Pismo that is a good question but I don't think any of the 502's were offered counter rotate
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Old 08-10-2018, 09:46 AM
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Agree ^^^ most of Merc's stock stuff back in the day were ext balanced, move the bell housing and coupler over and block mount a starter
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Old 08-10-2018, 11:19 AM
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Wanted to add for boaters looking for help --- good example here of one can never assume what the engine(s) really are for set ups --- so with that said it is always important to list all the important info first to get the correct answers. CARB engines NOT MPI.

Anyways info at hand ------------- if I recall CORRECTLY stock OEM Merc NEVER had a Right hand rotation 502 / 8.2 GM based engine period. They did have 454 's GM based engines that were right hand rotation.

Merc does have a service bulletin per engine rotation that came out about 20 years ago. I know I have it somewhere.
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