Raylar

Electrical1:
Not sure about the installation, but it sounds like the new engine builder and installer did a good job of doing a marine engine rebuild and clean up installation that is serving you well so far. It sort of sounds like the first time the installation and engine work from GM may have been substandard, but without knowing the real condition of all the cooler , lines, cooling etc., it may have been a case of throwing some new motors at some bad systems and therefore destroying the new engines. On older boats, especially those exposed to a lot of saltwater use its really a good idea to strip the engines and systems out of the boat and carefully going through each part and system with neccessary cleaning, rebuilding and replacement of marginal or bad or corroded parts and bring everything back up to new like standards, then re-install new or proper rebuilt marine use motors. This will usually eliminate the possibility of ruining brand new motors with old hoses, lines, coolers, belts, pumps, clamps, wiring and badly corroded or damaged brackets and fittings. I know its expensive to properly redo boat motors and associated sytems, but its much more expensive, agitating and depressing to have to do it twice! Sometimes I even think its a good idea to use a reputable and highly regarded marine surveyor and let him asess the condition of everything engine related on your own boat and then follow their recommendations. Just a thought.

Ray @ Raylar

fastestbowtie

I keep seeing these post and reading stuff like this and would really like to know wht is so different. I built motors for 10 years and have never seen a marine piston, marine oil pump, marine crank, rods or bearings... and until just recently marine camshaft and heads were non existent. I think the most critical difference (and perhaps the main thing you are concerned about) is that if it is fresh water cooled, you must give it more piston clearance because the piston will grow, but the incoming water will keep the cylinder from expanding as much as it would in a more controlled environment (such as a closed cooling system or car) causing a piston problem. Also as I understand it, Mercury and Volvo both buy there motors from GM heavy duty truck division before they "marinize" them. Granted this may not be true of Mercury Marines line of racing engines, but that is where i understand they get there other ones.

hillbilly24

Not to be an a$$ but if you built engines for 10 years you of all people should know there is a diffrence. Have you ever seen a "circle track oil pump" or a "drag piston" NO, but there are different parts combos that work for diffrent situations. The RPM range that a marine engine is subject to operating at for extended periods has alot to do with the diffrence especially when it comes to the valvetrain. The clearances are diffrent, head gasket material are diffrent, there are an awful lot of diffrences between the two. Can an automotive engine be adapted to work as a marine mill? yeah, but there are some things that need to be changed and you need to know what you are doing if it's ever gona last. You ever notice that the big names in the marine engine buisness like Cheif and Teague only build marine engins and nothing else ? It's a specialty market. Merc does buy all their base engines from GM, atleast all the black one's I'm not sure about the Blue stuff(racing division). They do alot to maranize them though, depending on the engine the only GM part left when they are done is the block. Cam timing and valve overlap need to be addresed becuase of reversion problems, you may have never seen a "marine cam" until recently but there are an awful lot of them that you would never want to put in a marine engine. Marine intakes have a brass or bronze insert around the water passage, Forged cranks become a standard feature at much lower power ratings then the automotive world. Unless you enjoy nuetral drops automotive engines are not subject to impact loads that occur when the prop leaves the water and then re-enters and there is nothing to take up the shock like a toque converter or a clutch to mash to the floor. Controlling Harmonics is much more important in the marine world because of extended hig RPM runs. The lost goes on forever. THEY ARE NOT THE SAME.

electrical1

Basically It comes down to a couple of things when it comes to boats, because there are different opinions on everything when it comes to boats. You can't get 2 people to agree on anything. GET SOMEONE KNOWLEDGEABLE WHO HAS A LONG GOOD REPUTATION AND CHANGE EVERYTHING YOU POSSIBLE CAN WHEN RE-POWERING A BOAT. EVEN THEN THERE ARE NO GUARANTEES. BOATS ARE TO EXPENSIVE AND THE SEASONS TO SHORT TO TAKE SHORT CUTS AND TO HAVE PEOPLE WHO THINK THERE MECHANICS WORKING ON YOU BOAT. THERE ARE ALOT OF MECHANICS WHO CAN CHANGE A PUMP OR PLUGS, BUT ONLY A FEW WHO CAN BUILD A MOTOR RIGHT. Like everyone said you don't see a car running at 5000 rpms for long periods of time ,except race cars and how often do race car motors blow (all the time) and they have professional builders.

PatriYacht

Read this thread about oil coolers and plumbing.http://www.offshoreonly.com/forums/s...ight=oil+lines When you get over 400hp and start winding the engine for long periods of time, you need a cooling system that can handle a lot of heat. Mercruiser always used to use 140 degree water themostat. Install water temp, oil temp and oil pressure gauges and use them. At the first sign of trouble slow down and investigate.

articfriends

iTrader: (1)

I still have a hard time believing that there is any kind of a basic problem with a 454 ho or 502 ho motor in a boat other than supporting equipment not being up to snuff(oil cooler,lines,jetting etc). Other than the camshaft and oil bypass valves on the block a 454 mag/502 mag is IDENTICAL internally to a 454ho crate motor/502 ho crate motor. My original 502 mag that came in my boat(2000 502 motor)didn't have "EXTRA LOOSE" clearences over any big block crate motor Ive ever had apart. They use the same j/e metric ring pistons at the same clearence's,same cranks,same oil pump etc. It boils down to 3 things,boat motors need a safe air fuel ratio or they will lean out and fail,a safe amount of timing that can be run for sustained period of time without detonation and the oil cooler,lines,bypass valves must be correct. Now if you were building a motor for power levels and rpm levels above the stock ratings,yes,you would set clearences up looser yet,looser valve stem clearences,wider seat margins,bigger piston ring gap,inconel valves etc. My point of this is gm doesn't send out ho big block motors with .001 piston clearence or .0008 thous rod/main clearence so it isn't like they are super "tight" like a std car engine,Smitty

vandeano

I have seen guys blow a motor and put in a new one with out cleaning oil cooler and lines , this took out the new motor fast. Just my thoughts.[/QUOTE]


Been there, Done that

TURBOED

i have a 454 and i've put about 30 hours on it so far on top of the previous hours and no problems,i think the problem was overlooked,is like changing a turbo and not changing the oil feed line or at least cleaning it,before putting motors in you have to figure out why it blew up to begin with,that's just my 2 cents.

Kidnova

Just thought this was worth reading again.