How many hours before a rebuild?
 

Looking at a 89' Formula 357. Has the stock Merc 420's (454 CI) and 500 hours. I am told they are original. I know to have a compression chk done, but 500 hours seems like rebuild time to me.

Second, about how much $ per side to expect.

Wannabe

Re: How many hours before a rebuild?
 

Don't know about the 420's but my 454 Mag just gave up after 550 hrs. I think the failure was mainly due to the crappy stock merc exhaust.

A lot of those hours were salt water hours and I ran it prett hard.

Re: How many hours before a rebuild?
 

After 500 hrs they at least need a valve job. For peace of mind I'd probably do the bottom end also. Instigator here on the board, just had his 420's rebuilt at Millenium Marine. Lenny, the owner, is a reasonable and honest guy. He rebuilt my 540's and did a great job.

Re: How many hours before a rebuild?
 

PatriYacht- where is Millenium marine, Detroit area?

Thanks Wannabe

Re: How many hours before a rebuild?
 

Millenium is in Harrison Twp. near I-94 and Metro Beach Pky. 586-468-7361 He stays in Mi. over the winter and builds engines for next season.

Re: How many hours before a rebuild?
 

I'm surprised at rebuild at 500 hours. Must be related to use--I'm told 1500 to 2000 hours in normal service should be expected.

I've got a pair of MarinePower 454 EFI engines with 700 hours and they check out, at least with the diagnostics we can do without pulling engines down.

Poorsche

www.boatmat.com

Re: How many hours before a rebuild?
 

I agree, start worrying in 300+ hours if well maintained and not severly abused. We all know it takes too many years to do that many hours up north.

Re: How many hours before a rebuild?
 

I just pulled my 7.4/330hp with 703 hours. I have to change the coupler and figured I would rebuild it during the winter. My engine ran good and had good compression and would have made it another season (with crossed fingers). After pulling it I saw that it d some problems that need attention. By the looks of the engine it was in a lot of salt. I'm looking at a budget of $3k for the rebuild minus the exhaust.

Re: How many hours before a rebuild?
 

"I'm surprised at rebuild at 500 hours. Must be related to use--I'm told 1500 to 2000 hours in normal service should be expected. "

For normal recreational usage I would agree w/ 1500 hrs. Hi-performance usage w/ more WOT time reduces that.

I am not sure the engines need to be rebuilt at 500 hrs. I was just looking for opinions and estimates. The $ 3k a side is abudget amount I have.

Wannabe

Re: How many hours before a rebuild?
 

in my 6 months of high performance boating I've never seen a high performance motor go 1500 hours ...much less 2000 ......

Re: How many hours before a rebuild?
 

Also ..I just pulled one motor ...both drives ...had the heads done ..resealed one drive ...serviced the other .....4000.00 ...

Re: How many hours before a rebuild?
 

how bout for us little guys....1998 350 mpi's turning bravo 1's...currently has approx 175 hours and first 150 hours were fresh water use. it is now being used in 100% salt water some brackish but flushed after every single use...boat usually cruised at between 35-3800 rpm's and when kicked in the a$$ 5000 rpms max @ WOT...whats the life expectency. Synthetic oil changed every 30-40 hours. ?????

Re: How many hours before a rebuild?
 

ABSOLUTELY. If a manufacturer claims thosuands of hours before rebuild, thats in a Bayliner.

Re: How many hours before a rebuild?
 

Depends on the engine. The 260 HP 350CID Mercs in my dad's 1983 F272 Formula still check out after over 20 years and 1500 hours. Those mild 350s last a long time. Build a 800 hp engine and you may get 200 hours out of it before a rebuild. Depends on the engine. But, I would think a mild 454 should be able to last a well over 500 hours.

Re: How many hours before a rebuild?
 

89 formula 260ss 330 B1 all salt water use, oil changed 2/season with 40 weight valvoline racing or castrol oil and not abused - lasted approx. 1300 hrs

Re: How many hours before a rebuild?
 

My last boat had 400 hp/ 454's. I sold it after 600 hrs and I'm sure it had a season or two left but it was losing performance. It depends how hard you run them. In a cruiser where they never go above 3500 rpm, I could see getting 1500 hrs in a well maintained boat. However in a heavy high perf. boat where the engines are run wide open a lot, 500 hrs is a lot. Also it's a lot cheaper to rebuild an engine before something breaks.

Re: How many hours before a rebuild?
 

Never seen a high performance motor wear out.The Valve Springs either break or get weak and the Valve touches the Piston :eek: .Next thing is the Rod Bolts or Rods stretch and break or touch the Valves(same results, your motor is junk) 500 hrs is the number on a HP motor,although you might get away with just changing the Rods & Valve Springs if you didn't want to do a full rebuild :rolleyes:

Re: How many hours before a rebuild?
 

I agree that after 500 hours on an Hi-Perf marine engine that you had better start thinking of a rebuild before too long. But as far as the connecting rods go, I don't think a connecting rod really needs to be replaced as much as it might need reconditioning and a new set of rod bolts---ARP rod bolts at that. Perhaps that is what Dixie Doug meant.

However, if you are going to go to all the trouble of tearing into the bottom end to remove the connecting rods for reconditioning and rod bolt replacement, then I would say it would probably be a wise idea at that point to just go ahead and rebuild the entire bottom end. :D

Re: How many hours before a rebuild?
 

As a marine surveyor in the Ft. Lauderdale area that specializes in performance boats I am asked this question many times. There are so many variables! How was the boat maintained and run? A compression test will tell you if the engine internals are healthy. The 420's had those monster cast-iron manifolds and risers when they first came out and were later changed to the Merc/Gil Offshore type. (Added another 5 hp.). If those engines have good compression and the performance is there, maybe a valve job will be all you need. The big block Chevy bottom end usually only fails if the oil wasn't changed often enough.

Re: How many hours before a rebuild?
 

Let me say in my post I meant motors with 500-600 hp.Less hp the more hrs you can go,the higher hp less hrs.
KAMMA ,I see you get the ideal