Hello all Motor experts out there, I am reaching out for any and all Opinions on the Merc Hp 500 EFI blue Motor. I am looking at a 38 Powerquest with these Motors 450 Hrs. on them. Have Not sea trialed the boat yet but have talked with the Mechanic who has serviced the motors for the past 15 yrs. He certainly has given them a clean bill of health and has a strong opinion that they are solid. Nothing has been done to the motors except standard maintenance.

I have read and heard some opinions on the service rebuild intervals. At 450 hrs. if the boat has spent 95% of the time under 3500 Rpm should i be concerned about getting into the boat and having to do a top end rebuilt or freshen them. I am confident the boat will run when i do the sea trial, its the after I get it home situation. Can these Motors run solid up into the 700-800 hrs range if they have been babied and taken care of. I just don't want to get into a 5-10K rebuild expense right away. It might change my opinion on the purchase.
I have always felt these motors were one of the best motors Merc ever built.. I have read some threads on the headers, still a little confused on the whole topic, any opinions on that are welcome as well.

Thanks in advance for any help and opinions

replace the valve springs.

I have had 2 boats with the 500 efi's in them and they were great motors! That being said I did do top ends on all 4 motors and they had around 400 hrs on them. I never did find one with a visible valve spring issue however its not to say they weren't weak. The issue that I did find on all 4 motors was the head gasket beginning to burn away in between the cylinder walls. If I had not replaced the head gaskets I am certain that all of them would have seen major issues from the head gasket.

I would not hesitate to buy another boat with the 500 efi's in it. However given the hours stated you do need to plan on doing the top ends and should probably look at couplers.

If you do decided to do it contact Eddie Young @ Young performance. Very knowledgeable in what you will need.

I had heard that from someone years ago, are they just week , not sure what spring merc used, Do u suggest taking the heads off and going through them totally ???

See previous post. Absolutely pull the heads.

Pull heads. Leak test valves-seats by filling ports with water. None comes out into chambers, at least they are sealed. Pull springs. Check valve guides. Check valve seats. Decide if you are installing new springs or taking them to the head shop. Check head and block decks for flatness and no sign of burning between cyls. If you take heads to shop with springs on, they can do 16 guides and seats and there is nothing you can say. Take them in springs off and they aren't so free to do as they please. Don't mix up valves.

I have them in my boat, they are good motors. I also did top ends at under 400 hours. If I remember correctly it was more like 350. They also go through head gaskets as well. I was in the same spot you are in now 5 years ago. It was worth it to go with the 500s

[QUOTE=soonenough;4562725]I have had 2 boats with the 500 efi's in them and they were great motors! That being said I did do top ends on all 4 motors and they had around 400 hrs on them. I never did find one with a visible valve spring issue however its not to say they weren't weak. The issue that I did find on all 4 motors was the head gasket beginning to burn away in between the cylinder walls. If I had not replaced the head gaskets I am certain that all of them would have seen major issues from the head gasket.

I would not hesitate to buy another boat with the 500 efi's in it. However given the hours stated you do need to plan on doing the top ends and should probably look at couplers.

If you do decided to do it contact Eddie Young @ Young performance. Very knowledgeable in what you will need.[/QUOT

Thanks for the reply, what kind of cost am I looking at to have the heads gone through .If I pull the heads off new head gaskets come with that anyway . I am familiar with the couplers as I have pulled many motors and replaced couplers on a few boats. Any thought s on the header issue that has come up not sure what is on a 2000 HP500 anyway. ??

I did most of the labor myself so I wouldn't know exact cost if you had someone do them from start to finish. I would estimate 3-4k per motor.

I haven't heard of header issues on the 500's. The 525 efi had the majority of the header issues.

I brought them up to 1300 hours!
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