New to this website, I am considering a 91 Scarab, dual 454's, with 460 hours on them. Owner is playing down the hours as low, claims 900 hr average before upper rebuild, 1200 hour on lower half. Looking for comments or numbers from anyone with knowledge of this type motor. Owner has NOT performed a compression check. You can respond here or e-mail info to [email protected]

You posted this in the wrong section, you should move it to technical Q@A. But to answer your question it first depends on which 454's they are. 460 is a lot but nothing to be scared of. On a mild 454, those numbers for rebuilds sound about right. taken care of, they will run a long time.

I think it depends more on how hard they've been run than how many hours are on them. My 1988 454 mags have just over 500 hours, no weird noises, no smoke, compression check last summer showed everything normal.

I put a 1000 hours on my 91 365hp 454's. I chose to rebuild them this year and the only thing really wrong were the valve seals, and the distributor was wore out.

If they been run hard plan on rebuilding them,i have a friend w/600 hrs on his 454 mag,it is getting tired,1200 hrs would be extremely optimistic!

My 92 330HP 7.4L was done at 516 hours. I always ran it pretty hard though.

I had a pair of 330 hp 454's in a 280 Baja. I lost one motor at 666 hrs due to a windage tray breaking (shrapnel in the oil pump drive shaft) The other motor is still running strong with over 900 hrs to date. This was a fresh water boat.

With proper maintenance, the low ho 454's will last quite a while.

correct answer ..... D. All of the Above ..... It can be widely variable .... a compression test will tell the big picture .... I would say at least 140 and all should be within 10% ... If compression is off ..leak down will tell where the Problem is .... but if they start well ...idle well ...good oil pressure .. they should be OK ... Everyone really makes a big deal about the motors ...and it is ...I did also.....but they can be made as new ....without breaking the bank if you go back as they are stock .. what you spend beyond that is limitless ....I would pay ALOT of attention to the exhaust Manifolds and risers ....If they are original they have to go NOW ... a problem there will destroy a motor ....
But a major thing to look at is the boat itself ....finish...upholstery ...etc ..those things can cost $$$ and unless you pay big big bucks it Will never be good as new ..... .02

My 7.4L/330hp had 780 hours on it when I pulled it for a bad coupler. Stripped the motor down and everything was in great shape. Compression was in the mid 140's across, and the I could have gone another year easily, but like everyone else I needed more power and dropped in a 540...

My 454 mag died at around 500 hours. The motor went pretty quick. Over a week or two I lost 7mph. Broken rings and bent valves were it's demise. Guess it all depends on how the motors were run. Personally, I'd consider any high performance gas engine with over 500 hours to owe nothing for life. Keep on running them, but don't be suprised when your season is cut short.