Rookie2mbit

Hello, I'm new to this forum, and also to boating in general.

I'm a bit used to doing V8's, but SBC's and in cars.

Now, a guy asked me to take a look at his 454 Mags from his twin Mag boat.
He has 3 shot 454 gen 4 Mag's on the floor now...

They are, being gen 4's, I believe, from 1990-1991.
I looked up the casting numbers.: 10069286.
4 bolt mains, Rochester Quad's.

Same problem with all 3 engines.: all mains and big ends totally shot.
Runs 15W-40, remote filters, seawater-cooled, 3" headers.

Engine No.4 is still in the boat, sounds right, but oilpressure is never exceeding 30psi, no matter the revs or temps.
Boat has all electronic, boat-manufacturer's gauges, seem crappy to me...

Now, he's had nothing but trouble with these engines since day 1.
He's been calling like half of Denmark(yes, that's where we are at...), and everyone tells the same story: 454's don't last in boats.

Personally, I don't buy that.

He says the rev limit is 4500rpms at WOT, the screws keep the engines there.

He has Mercruiser drives.

Both engines are CW's.

He's not the kinda guy who thrashes the engines when cold, or runs them at WOT for like hours on end.

We are ordering a new, standard crank, shells and rods for one of the 3 engines on the floor, to rebuild it.

What clearances do I aim at for the mains and big ends, and what axial clearance for the crank?

What oilpressures do we need as a minimum?

What temps(oil+water) should we be within, and what degrees F thermostate do we need?

I've searched and read a lot of pressure-related posts inhere, but the answers are kind of divided.
No HV pumps or anything in these engines, straight off the rack stuff.

Any help is appreciated!

Regards.Rooks,Denmark.

stevesxm

does this boat weigh , like 15,000 lbs or something ? and does all this damage happen in the first 15 minutes or the first 150 hours ?

454's will last just fine if built properly, loaded properly and lubricated properly. the reason i ask the first question is that i chased a problem like this where the guy had detonation problems at all timing and mixture combo's with a small block...... we explored every single possible motor issue unsucessfully until he finally thought to mention that the boat weighed 12,500 lbs. so the thing would just sit there at WOT trying to go until the combustion chambers would melt...

at any rate... if all things are equal, i would have to guess that if you are so comprehensively running the bottom ends out they are either excessively loaded for excessively long and as such, driving the oil temps up to where there is , effectively, no lubrication. what else would kill the rods AND the mains ?

and i would suggest that unless you have an exceptional machine shop avaialable to you, i would be seriously concerned about using those blocks as cores.

i realize i am not answering your questions about the numbers but , if i were you, i would want an answer to the cause of the failures before i considered doing anything at all. without that, i would suggest that any money you spend now, you may as well just pile in the middle of the floor and light on fire and save yourself all the shipping.

beyond that, i wouldn't trust any of the junk you have on the floor except the accessories.

buy new long blocks and never look back.

DareDevil

I say to much load is the problem,,,4 main had 5200 RPM max. I had them in my old boat with over 400 hours and still running strong ,,i rev. them all the time to 5400 RPM in a 7 K pound boat with twin Bravos.
I think the props are to big ,,,oil press should be ~ 70+ @ WOT and 215 degree fahrenheit .

What boat and gear ratio ,,,what drives and do u have a picture of the setup ????? All this would help.
Is it a performance or a cabin boat ???

Also with 3 " exhaust do u mean the end pipes ???? way to small ,,,to much back pressure , he is choking them to dead !!!

4 " is a minimum on a 454 ,,,,i say !!!!!

If u just build them a little loos you are fine .

Don't know the exact clearance ,but i bet somebody will chime in and let u know.

GOOD LUCK !!!

14 apache

Cut the oil filter open to see if it is collapsed in side all of the paper will be pushed together. That would limit the oil pressure in bypass mode. It would not filter the oil in bypass mode.

stevesxm

three times in a row ?

crapr6

This info is straight out of the Mercruiser service manual for 454 GEN 4 engines so I hope it helps.

Main bearing clearance (service)
.001-.003 IN
(.03-.07) MM

Rod bearing clearance (service)
.003 IN MAX
(.076) MM MAX

Rod side clearance
.013-.023 IN
(0.35-0.58) MM

Crankshaft end play
.006-.0010 IN
(0.15-0.2) MM

articfriends

Sounds like oil pressure issues. Have the oil coolers been replaced and lines flushed after having the first parts failure? I have a friend that is arrogant and hard headed,he bought a 22 ft scarab runabout with a 502 mag in it that was destroyed as you describe,mains were blue,heat cracks in crank and block,bearings melted. I offered to build him another 502 from parts I had and my price included replanig the oil cooler and flushing the lines etc,he chose to go another route. I still tried to help him with friendly advice which he chose to ignore. He had a shop build him a fresh 502 which was installed with his old oil lines and cooler. He flushed the cooler with "a little paint thinner" ,within 10 hours the motor was blown exactly like the old one,crank was blue and cracked,mains were melted,rod journals were ate past copper into the steel backing,etc,etc. When I looked over everything I found he had the soft block oil bypass valves that come in crate motors,a couple of small oil lines that were made by a hydraulic shop that were so restrictive they made the block valves open and bypass the cooler and filter. He couldn't believe this stuff could have caused his problems so I didn't waste anymore time trying to even give him advice. He built a 540 next, which is currently in the boat,has about 3 or 4 hours on it, oil pressure is around 25-30 at wot and less than 10 at idle. He used the same junk that I told him to throw away,he says these gen 5 and 6 502 blocks are just junk and must be causing his problems.
Your friend needs to see what the common denominator is in his failures unless he is getting old, tired motors that are ready to puke and finishing them off,Smitty

JIMG

what arctic said is right. the stock 454 mag is extemely durable. you can beat them all day and do it again tommorrow. unless you use an old cooler on a new engine. then it might only run for a few minutes before tearing the mains out.

1BIGJIM

I think Smitty hit it on the head

A learning experience myself, I once used an oil cooler after spinning a rod bearing. I thought I cleaned it out because I could not see anything inside it. Well after the next engine went belly up (same thing) After reading and taking advise on this forum I replaced the cooler and had new lines made.
Next engine was still running hard when It found a new home in Michigan this spring.

I saved the old cooler and cut it open, after looking inside one there is no way you can clean the metal shavings out of one once you spin a bearing.

Rookie2mbit

Thanks for all your replies!

Now, it's a racing-type boat, open thing.
I think it weighs about 8000lbs roughly, american built, originally with Mercruiser engines and drives.

No, he did NOT change oilcoolers, I'm 99% sure about that.

All lines and accessories are the ones that came with the boat, I guess, as I don't think anyone messed with those at all.

Remember, Denmark might be a boating-nation, but VERY small, 5.5mill inhabitants.
Might only be like 30 or so of these boats here, if that many, so just seeing one is extraordinary.

Though, I might be wrong, but it's certainly not something I've seen more than 5 of in my lifetime here.

So, tuning and modding and what not is only done by a few, as you can imagine.

I'll take pics during this week, and post them, so you can have a closer look at things in general.

First engine blew due to someone not opening for the cooling or whatever it was(boiling the oil off), second time it just threw the mains for some unknown reason(after 1st rebuild, maybe old oilcooler), and 3rd time it made a milkshake, due to a leaking intake manifold, he says.

Actually, he even has a 4th engine on the floor off another boat, which was supposed to be OK.
We grabbed the crank of it, felt lash, removed the mains, and they were all gone too, as well as all the big ends.

Anyway, I'll post some pics before we go further.

He intends on running these two Mag's this season, then swapping to 2 new 460HP longblocks, also 454's imported from the US, if you guys don't have any better suggestions for new engines.

Oh, maybe the exhausts are 4", they're Mercruiser items, I guess.

Regards.Rooks.