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OliverM5
04-12-2007, 07:26 PM
A buddy of mine is looking at a 35'+ Fountain with twin HP500's in it. It looks like the motors have quite a few hours on them without a rebuild. My question is:
1) How many hours before a rebuild?
2) What does a rebuild cost and involve?
Thanks!

TCHB
04-12-2007, 07:53 PM
I do not think hours tell the whole story. Most boats spend half the time at idle (channle time) or slow cruising.

Infomaniac
04-13-2007, 05:31 AM
Valve springs are dead at 120 hours or so. You don't realize it until you have the heads done and pick up some more RPM. And it is a gamble to reuse the valves if you just have the heads serviced. They can pop a head off of a valve for no apparent reason. More likely if you have run them way past 120 hours.
It's about $5,500 per to do a complete rebuild here at my shop.
Heads are a ballistic change everything. Engine is pistons timing set oil pump rings bearings machine every surface and blueprint assembly. Lifters depending on the number of hours.

Infomaniac
04-13-2007, 05:54 AM
[QUOTE=Infomaniac;2499737]Valve springs are dead at 120 hours or so. You don't realize it until you have the heads done and pick up some more RPM. And it is a gamble to reuse the valves if you just have the heads serviced. They can pop a head off of a valve for no apparent reason. More likely if you have run them way past 120 hours.
is that on all 500hp?i have a 2001 500hp efi and was told i didn't have to do that is that right?
I would read the factory Merc manual and see what they recommend. Do you have the EXACT wide open RPM as you did just afer new break in?
My opinion is based on what I see come through the shop.

Not So Fast
04-13-2007, 06:25 AM
Valve springs are dead at 120 hours or so. You don't realize it until you have the heads done and pick up some more RPM. And it is a gamble to reuse the valves if you just have the heads serviced. They can pop a head off of a valve for no apparent reason. More likely if you have run them way past 120 hours.
It's about $5,500 per to do a complete rebuild here at my shop.
Heads are a ballistic change everything. Engine is pistons timing set oil pump rings bearings machine every surface and blueprint assembly. Lifters depending on the number of hours.
Valve springs dead at 120 hrs, really???????? That does not seem like much use at all to me, is that a malady to earlier HP 500 or to all? Mine is a 2004 and I've never heard of this problem. I can maybe see this problem in a race boat situation where its being run very hard but for a pleasure boat thats been seviced (oil change every 20-25 hrs) and driven with any sense of safety its hard to believe an engine part is worn out at 120 hrs, of course I'm not a marine mechanic and I certainly dont get to see these things on a daily basis as you do either. Also you say that the valves themselves are unrealiable at this point??:( Any info is appreciated. Thanks, NSF

Not So Fast
04-13-2007, 06:56 AM
[QUOTE=titties and beer;2499747]
I would read the factory Merc manual and see what they recommend. Do you have the EXACT wide open RPM as you did just afer new break in?
My opinion is based on what I see come through the shop.
After reading your comments I thought I would look at your highlighted website and I was impressed by your storyline on the Josh Hay HP 500 build-up. Things like that make you much more creditable IMO, nice job ;) NSF

Infomaniac
04-13-2007, 07:02 AM
Yep someimes I post too fast. And I did state what I did but it needs to be taken as just another opinion.
Mainly earlier HP 500's are suspect and the longer they are run with dead sprngs the more unreliable the valves are.
I have seen some later models with dead springs and some without. So from a machie shop perspective they all need replaced. And the engine has seen worst case scenarion operaton.
Lets say you take your heads in for whatever reason and the machine shop grinds the valves etc and you put them back on. Another 30 hours or so the head pops off a valve. Who will you hold responsible? You can measure wear to the stem and true up the valve seat. But you cannot measure metal fatigue.
An engine with 300ish hours that still has factory springs for sure has been hammering the valves.
It is impossible to determine how often the engine was run WOT. How often the oil was changed etc. If you buy the boat used it is a gamble.
So if I may revise what I stated:
I would seriously look at the springs at 120 + hours and use none or some loss of RPM as a judge. If so change them. The second 120 + or so hours the valves IMHO are ready to be replaced. With fresh heads do a oompression test and use that along with oil pressure and filter inspection to determine whether to freshen up the bottom end.

Baja Big Dog
04-13-2007, 07:15 AM
We cn beat this thing to death, (the springs thing). But the bottom line is the cost involved to change them when the heads are off for a rebuild is minimal compated tothe cost of doing them later when the motor is together.
Bottom line......change the friggin springs. The mount of times you change the oil has no effect on the performance of the springs.
These Oakies do know some stuff!!!!:mad:

Not So Fast
04-13-2007, 07:23 AM
Yep someimes I post too fast. And I did state what I did but it needs to be taken as just another opinion.
Mainly earlier HP 500's are suspect and the longer they are run with dead sprngs the more unreliable the valves are.
I have seen some later models with dead springs and some without. So from a machie shop perspective they all need replaced. And the engine has seen worst case scenarion operaton.
Lets say you take your heads in for whatever reason and the machine shop grinds the valves etc and you put them back on. Another 30 hours or so the head pops off a valve. Who will you hold responsible? You can measure wear to the stem and true up the valve seat. But you cannot measure metal fatigue.
An engine with 300ish hours that still has factory springs for sure has been hammering the valves.
It is impossible to determine how often the engine was run WOT. How often the oil was changed etc. If you buy the boat used it is a gamble.
So if I may revise what I stated:
I would seriously look at the springs at 120 + hours and use none or some loss of RPM as a judge. If so change them. The second 120 + or so hours the valves IMHO are ready to be replaced. With fresh heads do a oompression test and use that along with oil pressure and filter inspection to determine whether to freshen up the bottom end.
Thanks and good response. Like you said its hard to tell what an engine has had for a life. When we did the switch (from a 496HO) we took the original boat (same year as mine but different builder) out to test the motors performance and it ran flawlessly and the rpms were right on according to Merc, no problems at all and i trust my mechanic completely (my cousin), best wrench I know of IMO. He did the R&R and checked all things thouroughly (sp) before the install, draining the pan oil, cleaned and checked the oil cooler for any blockage and what ever else you mechanic type guys look for. Ha gave it a clean bill of health, also has serviced the boat since new. I havent had much time with it yet but what little time I do have has been very positive, runs pretty hard to me!!:D
Since we are on the subject can you tell me what the EFI 500 makes on dyno runs in stock form? I've heard the 496HO made 431 and the EFI 525 makes 560? but never heard about an HP 500 (EFImodel). Thanks for alll the info!!!! NSF

BALLSDEEP
04-13-2007, 04:13 PM
A buddy of mine is looking at a 35'+ Fountain with twin HP500's in it. It looks like the motors have quite a few hours on them without a rebuild. My question is:
1) How many hours before a rebuild?
2) What does a rebuild cost and involve?
Thanks!
Had mine rebuilt last season after 300 hard hours. As everyone stated, replaced the valves, seats, springs etc... Had a complete rebuild fortunetly nothing was broken, worn, or needed replaced for $4500 which also included dyno time.