Merc. 500 HP info
 

Anymore I am a much bigger fan of EFI engines, but I found this 33 outlaw that could be a pretty good deal and it has twin Merc 500 HP engines in it and of course these are carbuerated motors. I have heard those engines had some problems with valve springs, but other than that I have never really gotten any feedback on them. The engines have about 270 hours on them. I definitely don't want to get something I will be wrenching on all of the time. Does anyone know what kind of reliability these engines have, or any problems these engines are notorious for? Any info would be greatly appreciated. Thanks!

My HP500's had the spring melt-down at about 300 hours...
...inner springs had been in pieces for a while, continuing to destroy the top of the heads, then more broke off into a cylinder, and caused crankshaft to break in half.

I would recommend redoing the heads with stronger springs, and then they should be fine.

Carder

I have seen them run 400 hrs and no trouble but it just depends on the guy running the sticks!

Actually the guy running the sticks is a minor player in the spring melt-down.
Merc went to stronger springs after they were determined to be the weak link, also water reversion with their bad cam/ exhaust combos added to spring break-down.
If longevity was soley due to how the sticks were fondled, I would have been able to drive those engines forever...
Carder

those motors have a well known history for valve spring and water reversion issues in the models that didn't have the higher risers. As long as they are caught in time, no big deal. One suggestion mercury had to control reversion is raising idle speed, but changing to taller risers is by far the best fix.

I remember seeing that Bob Teague talked about this issue in depth in one of the teagues on tech section of powerboatmag

Thanks for the info everyone. How much does it usually cost to upgrade an engine with these specifications?

it depends on how much you can do yourself. the heads are going to have to come off. once off, your looking at less than 1K an engine for the valve spring, lock, retainer replacement. They need to thoroughly inspect the heads including the valve seats before they go back in.

The exhaust risers are a different story. You might need to take a picture of one of your existing ones and post to determine if you have one of the earlier "bad" designs or if you are ok. You can find some different risers that are compatible with what you have, you just may need to ask around.

Thanks again everyone I really appreciated it. So with everything said, would any of you buy a boat again with these engines in it?

Once the springs are done these engines run great. The rest of the peices in these engines are all good quality parts . :ernaehrung004:

If that 33 OL is in even average condition with the 500HP's its a steal at that price. Figure another 10k for the trailer and to do the valve springs.