kragar

looking at a boat with twin carbed 500HP in it. Everything is stock, freshwater boat. Wondering what issues this motor or accessories had and also, what rpm range did this motor run from stock.
Do they require any or more maintenance than a stock 502?

SC288

Mercury had a bad run of valve springs from their manufacturer so it would be a good idea to replace them if they have not been already. I know most people were replacing them after 2 - 300 hours but I would think even if th engine is 12 or more years old with low hours it would be a good idea to replace them. As far as maintenance goes there really about the same. Power starts falling off after 5200 RPM.

MILD THUNDER

iTrader: (3)

What sc288 said. Original valvesprings should have been replaced at 200 hours, they were known to be weak and or break. Other than that, they are nice engines. Basic, nothing fancy, and run good.

Young Performance

Those are some of the best engines that Merc ever turned out IMO. I love those engines, and I build 99% efi engines
Eddie

POWERPLAY J

Totally agree! Almost bullet proof, easy to maintain and run great! Had mine bumped to a lil over 600 and they are turn key any day of the week. Just hit 140hrs since build...

MILD THUNDER

iTrader: (3)

Hey Eddie, I am correct in assuming those 500 mercs came with gm rods and cranks? I know the bulldogs had aftermarket carillo rods or something similiar, wasn't sure about the HP500?

I know a friend of mine had a pair that had larger roller cams installed, a little work on the heads, and everything else stock, and they pushed a 31 bullet to 80mph. Ran great!

Young Performance

Yes, they have GM 7/16" rods. It is the exact same piece as the 500 efi except the camshaft (and of course the induction). The efi has a little larger cam on a 114 as compared to the 500 hp on a 110 center. The hp has Gil manifolds instead of the Etops on the efi. Both great pieces, but the HP's were simple and lend themselves to easy upgrades. They already have a Dart intake, so that's one thing you don't have to replace right off.
Funny story: I was at Dart checking them out a LONG time ago. Happened to be in Detroit and had been using their products for years. I had never met anyone there, so I figured I would stop by. As I'm looking around, I see a guy grinding on a HUGE stack of intakes. They had DART casted into the intake since it was part of the mold. The guy was grinding the Dart name off of them since it was raised up above the surrounding intake runner. I was very confused since I could not imagine why he would be doing that. After all, if they were going to grind it off, then why put it there in the first place. I couldn't stand it.....I had to know why. I walk over and ask the guy what the hell he's doing. He's reply....these are going to Merc for the 500 hp. That way, Merc can charge you $1000 when you need a replacement intake. All of a sudden, it all made sense. I guess I really wasn't that surprised.
Anyway, you can't go wrong with a 500 hp. Excellent engine that can easily be upgraded to 600 or more.
Eddie

kragar

Thanks guys. motors on this one I am looking at are at 300. He says they are untouched. Boat has been on inner lake most of its life
An idea what a pair of 500s in a 29 outlaw would push the boat to in fresh water?

Young Performance

Then plan on doing the heads....springs, 10* retainers and locks, seals, etc with 300 hours. Also, if they are untouched, then all of the seals should still be in place.
Eddie

kragar

I dont mind doing the heads. can still leave motors in the boat then.
Thanks