I am pretty new to boating I have a 1998 advantage with a hp500 in it. I have been told I better change the vaulve springs? Is this all I have to do? The boat runs great and I would like to keep it that way. I was told to put crane springs in it, but is there a certain kind? The motor I think is stock with 300 hrs

Merc stopped using Crane and went to Comp, I think the part number is the 929 Dual spring. I was told 250 to 300 hrs on springs with performance roller cams. Isky also makes a spring I think the part numbers are 8205 or 8205 plus.

At a minimum, change the valve springs. A valve job could be needed as well. You can do a leak down test to check this.

Just wanted to say thank you.

Hey all im try to gey some ideas with my 454 mag im rebuilding. What make a 500hp thanks

Bore & Stroke your block to 489 or 496. Aftermarket exhaust, new intake & carb, new roller cam, roller rockers, valve springs, oil cooler. Heads will be fine with a little port work. Its not that easy to get HP in a boat.

Just a update on the Comp springs. They are currently on backorder for about 3 more weeks. Maybe it was for the better anyway, that forced me to get the Iskys from RMbuilder. I ordered the 8205 plus endurance spring.

hope you having it running soon, i pulled the heads on my 500efi's and found 2 broken inner springs last year and also 1 loose valve seat. if i would have only changed the springs without pulling the heads i dont know if i would have found the loose seat[ machine shop found it ] this was at 175 hours

Wow, only 175 hrs. As a rule most guys were changing at 250hrs. I wounder if you had the Crane springs? I heard the inner springs are prone to failure. The Iskys were recomended by many people on OSO.