Read a lot of posts about changing valve springs and would appreciate a little more detail. I plan to use Comp Cam 929-16 springs but do not know the appropriate Comp Cam retainer # and keeper # part numbers or the valve stem diameter?
I have a stock, still sealed 98 hp500, 275hrs with Gil exhaust and thought I needed to remove the headers but understand that it is possible to get the valve covers off without removing the headers via a 1/4 inch drive socket, do I have this correct? Possibly the last question, can you describe the spring compressor tool used or have a part number / brand or something to get me going in the right direction. Thanks in advance

Yes you can remove the valve covers without removing the exhaust manifolds, a 1/4" socket set up is the ticket for the outer nuts. Not sure if you can change the springs without removing them though. My 500's were out of the boat when we did the springs.

Would recomend the Isky SP springs vs the Comps, a little more money for a lot more quality. Just an opinion. I used the Isky retainers and their 10 degree locks.

At 275 hours you're wise to be doing this.

If I am reading this correctly you have '98 carberated hp 500's. If so I suggest you look into replacing the valve lifter at the same time. My lifter "tie straps" failed at about 325 hours and took out a motor. Learned that the failure was common. Just my .02

Thanks for the info guys.....I sent Comp Cams a tech question this morning asking for the part numbers of the retainers and locks for my particular engine with 929-16 springs and will post numbers if they respond. Still looking for advice from someone who changed springs on the engine/ in the boat, with headers mounted and what tool they used to compress the springs. Thanks in advance

+1

That is the springs I went with.

remove the headers, air in the cyl use a arm type compressor that works off the rocker nut, pain in the a$$ on a twin engine boat but doable...

Talked to a marine engine builder and the below answers many of my questions concerning parts. It is also the consensus of many members here that the springs can be changed with the headers mounted although it is more difficult.

The engine builders preference on the Springs is always the Isky over the Comp. The best choice here would be the 8005+ endurance spring. If using a 7° retainer the part number is 175 – ST and the keepers are VL-800.

Thanks to everyone for their help

Let see if I can refresh this old thread.

The Comp 929-16 springs have been discontinued. What is everyone using now? Retainers and locks too?

If you'd like a ballpark idea of what the spring requirements are, use the calculator halfway down this page:

Valvetrain Engineering Services - Allmond Marine