n2boatn2

What do you think about those engines having 290 hours on them, they are 99's is it time for problems? they have been maintained by a Merc dealer and the boat is owned by a MATURE person, any help would be helpful,, Thanks

baja36ft

1999 had bad valves springs be careful and check it good i did a complete
rebuild at 290 hrs and all ways changed oil every 20 hrs!!!!!!!!!!!!!

dreamer

id did mine at 350... 17k ... but now theyre better than new 520 hp

Mudball

I have a 1999 HP500 carb engine that I bought with 180 hours on it.

Since these are known to have valve spring problems, I redid the top end of it then.

All the springs were very weak, and two valves were spinning. The head gaskets were not leaking. Everything else looked perfect.
I had a valve job done, and went back with Felpro head gaskets (the Merc head gaskets are junk). I also went with new Comp Cam 929-16 springs, and new retainers and keepers from Crane.

Some others (on another forum) had far worse happen to theirs, even close to the 200 hour point. A few had leaking head gaskets, bad valve seats, and broken springs.

If a spring breaks, you can start to tear up lifters, cams, and the metal can do all kinds of damage to things...
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I believe you are running on borrowed time! At the very least, change out the valve springs.

Take care,
Kent

kevinr

Just did rebuild on two, for customer. Changed cam ,springs ,intake , and carb only.Ended up on the DYNO 570hp , 622ft lbs torque at 4,500 RPM's. also made 500ft lbs at 3,000. we did re-balance, blueprint also 9.5:1 on pump gas.
Kevin's Machine & Engineering (Hawk Marine)

Ran-Dom 32

I just tore apart my '99 HP 500's (325 Hours) 1 side had 5 or 6 broken springs - (funny thing engine ran fine before pulling apart) doing complete head job on both engines.

Mudball

Cool!! What was your retrofit recipe?

kevinr

Just lucky i guess!!! kidding . no really the engines looked real eficient on the dyno. otherwords simply put for all the air & fuel put into the eng. Maximum torque & power came out. No hidden secrects here, just on the shelf parts were used, crane marine hyd roller cam,JE small dome,stock every thing else,not even any port & polish on stock rect. port heads. They were balanced & blueprinted. I try to take sewingmachine technique to building engines..........

Madmax

Don't mean to hi-jack a thread, but if anybody is interested, I have a brand new set of Crane 929-16 valve springs still in the box that I don't need since I sold the boat. I will sell them for $100 bucks plus shipping. These are the springs Teague reccomends to replace the Hp500 springs with. Anybody interested, write me at [email protected]

thanks.!

800XCR

iTrader: (2)

I am rebuilding my 500's as well. How do you get 9.5:1 using flat top pistons and stock Merc (GM) heads? Thanks