When too many engine hours ?
 

For the used high performance boats, when are there too many hours (assuming boat was run hard) and need to just move on and look at another boat ?

In reading the different threads, it looks like the stock 454's hold up well to 300 hours, the 496's need to be rebuilt after 250 hours, the 502's/525's need valve springs replaced after 225-250 hours, is this correct ?

If the engine is super-charged, I know that this shortens engine life, but by how much 25%, 50%, etc., ?

WE have over 225 hrs on our Rudy Dryden built ICE injected 1300+ hp blown power and have yet to remove our valve covers. We twist these hydraulic roller mills up past 6500 rpms every weekend.We hope to see 300 hrs before a freshen up.

It all depends on the builder, components used,tune up, vigilant oil /water temps,oil change durations as well as luck.

thanks,

I was more referring to the stock motors that probably most of the performance boats have when bought off the show room floor.

a stock 454 will run 1000 + hours,,,, not 300 if serviced correctly

Stock 496's should go 500 hrs before a valve job and 1000 before the bottom end needs rebuiding. a Hp 500 or 525 should go 300 or 400 before a valve job and 600 to 800 before the bottom needs rebuilding. Of course some people can break a bowling ball in a sandbox with their bare hands. :lolhit:

some people can break a bowling ball in a sandbox with their bare hands.:eek:
Hey mmmmm c'mon now it was just that 1 time .LMAO:bigbird::drink:

I'm a total freak on the importance of the oil type and frequency of oil changes. You can get well over 500 hrs on stock big blocks (454, 502, 525). My previous boat had 900 hrs with minimal compression loss. We burn Shaffer 20W-50 synthetics and change oil every 30-40 hrs. Many Sprint cars are running the same oil with great results. It's the best keep secret.

Stock 454, and 502 go into the 1000's. We have 670 with good compression numbers. Knock on wood.

I get 250 to 300 hours out of my ProCahrged 454 and run tuff most of the time 720 HP. I change oil at the first sign of consumption. Typically every 18 to 20 hours. 50W Valvoline Racing Oil.

I don't know what threads you're looking at:confused:

Stock 454/502 mags are good to around 1000 hrs. Maybe a valve job and springs at 500hrs.

The newer 496HO and HO mags are the same way.

500efis and 525EFI's will need valve springs in the 250-300 hr range and possibly rebuilds in the 500-600hr range.

All depends, a well maintained stock motor may last 1000hrs. In salt water it may last 500 hours. If the exhaust is leaking water it may not last 300 hours. I remember going through this thought process when I bought my boat with 20 hours on a rebuilt 454. I thought it would be good for 500 hours, but the guy used non-marine aluminum heads so they didn't make it 30 hours. Don't make my mistake.

TexomaPowerboater, so would a surveyor or local boat mechanic have caught this issue with non-marine heads or do you have to dis-assemble the engine somewhat ?

Please educate me, what is the difference between marine and non-marine heads ?

What else should I be looking at (in terms of parts) when the engine has been rebuilt to make it marine worthy ?

In our previous boat, we put about 800-850 engine hours (mostly salt, flushed after every use) on a stock 496 in a little less than 4 years. No compression loss and no oil consumption. Just sold boat last month.

All I had to do was keep up with all the maintenance and oil changes. Avoid overheating like the plague. Actually broke it in per manufacturer directions but this boat did spend good time at both the lower and higher RPM ranges during use.

Definitely one of the top reasons for engine failure.

LOL, I had mine surveyed AND thoroughly inspected by my most trusted merc mechanic. Even did a compression test. A surveyor would not catch that. He might if you have him do a compression AND leakdown test, but that's only assuming the heads are already leaking. My non-marine heads were pro-comp and designed for drag racing. They were made of aluminum and had no hard coating for corrosion (i.e. non-marine) so the water passages corroded to the point that the gaskets couldn't hold a seal (on one engine), the other engine dropped a valve. They were designed to use anitfreeze which doesn't corrode. There are other differences in marine vs non-marine heads, but I don't know all the specs. If it's a custom built engine or rebuild or stock with major upgrades- find out what kind of heads are on it and do your research. If the seller wants to sell the boat he should be able to find out what kind of heads are on it. If it's stock with no mods - no worries.

Exhaust is the other biggy. Lots of guys selling boats with manifolds/headers at the end of their life. When the exhaust start leaking internally; water gets into the engine and kaBOOM!. I would think you would have to pull the exhuast to find out if their leaking, but there maybe other ways.

Does anyone know if there is a way to check for exhaust leaks without pulling the manifolds/headers?

I have 500hp carbed, with about 300 hours. How do I know that I need valve springs? The boat runs just as good as it ever has.

300 hours on carb 500's I would do springs and lifters.
My 496HO's have 530 + hours on them. Good compression, no oil consumption. Hours aren't as important as maintainence and type of usage. I scanned the ecm's, 250+ hours were under 1500 rpm's, only about an hour and a half at WOT.
150 hours at WOT and you have a tired engine.
No oil changes and 150 hours, still a tired engine.
There is no crystal ball. Get a survey, have the ecm's scanned, and have a reputable tech check the compression and look them over.
Then cross your fingers and pull the trigger.
Breaking stuff is a part of high performance boating, so consider some repairs in your budget.

I had my boat surveyed when I bought it last year and things checked out well. Last month, I had my drives serviced, and my mechanic also said that everything is great. The boat is in great condition, as it is a 98 model with that low of hours. I am just curious if there are any warning signs, and also how much $$$ I am looking at, having the valve springs done? I am not a mechanic, and I don't plan on doing anything further than change the oil.

Valve springs are about the only weak point of that motor. If it were my engine, with 300hrs, I'd change the springs. An ounce of prevention.........


Darrell.

With 300hrs, you definately need to have the valve springs changed. I would bet that several of the inner springs have cracks. The carbed 500hp springs had all kinds of problems with them breaking between 200 and 300hrs.

Its not an "if" they break situation...its more of "when"

You will be much better off to have them changed now. If one breaks badly, it could cause severe engine damage.

How much labor cost should I expect to pay to have them changed out? Also, what is a good cost on the new springs?

I believe this is correct for the 500's:

Comp 292
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Comp 292 (16) $124.99 929-16 - Comp Cams Dual Valve Springs -- Jegs and Summit Racing has them

Isky 8205 Plus
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http://www.iskycams.com/pdfcatalog/2004-05/page42.pdf
Isky Racing 8205 Plus (16) $285.95

Is it true that only the early "carb" 500hp's had the valve spring problems ? According to previous threads, the HP500's run camshafts with high lift and steep opening and closing rates which was hard on valvetrain components. Does anybody know what years the 500's have this issue or is it for all of them ? Why doesn't the 500 EFI have the same issue or does it ?

The early HP500's had problems with reversion which led to a lot of moisture in the engine and rusting valvesprings. Flawed valvesprings break easier. Mercruiser responded by changing the exhaust to eliminate the reversion and they changed the valvesprings to a more durable version. I think the problem was solved by 1998 but the valvetrain is still hard on parts and needs more maintanence than the 496's.

Don't forget to change the lifters when you do a valve job or change the springs. Roller lifters on high lift cams fail frequently and when they do the results are disasterous. Pieces of metal go everywhere inside the engine. It gets embeded in the piston skirts and ruins the bores. Don't assume the lifters are good for 1000 hrs. Wonder how I know this?

GET IT DONE. 300 hours is way to many and pushing your luck. One second running strong, next second, bilge filled with oil and major damage. Not putting a damper on things, but it has been talked about 200+ times on OSO. Just do a search. Don't take the chance. It is cheap to do. It will be ridiculously expensive if you don't. Just 2 cents

How much should I expect to pay for labor on this job? My reason for asking, is I just got a huge bill just for impellers and drive servicing, and I want to make sure that I don't have any surprises.

Labor shouldn't be that much. The springs can be replaced without pulling the heads by putting compressed air in the cyld and using a screw type spring compressor. If you have any mechanical skill you can do it yourself in a couple hours. Now, the question is, where do you get the springs? Crane Cams is history.

i paid $1200 for twins including all parts (and plugs) but that was over a year ago.

jim