Toasted the bearings. Anyone Know why?
 

bought a used low hour hp420 . never opened up the oil pan because I saw it run on a stand before i bought it. All seemed good. I put some afr heads on it and put it in my boat replacing my 310hp 454mpi . used all the accessories and oiling system from the MPI. 15 hours since i put it in. I running 5k rpms ..it dropped to 4.5k so i slowed down to idle . oil pressure was 0 -10 psi
shut it down. towed it back. at home i started it up the hose and could hear loud squeaking in the bottom of the motor. pulled the motor and all the bearings are worn thru the first layer to the copper, some just specals and some all copper. it did spin #5 rod bearing. coolant temp was always 175. oil pressure always 40-60psi . mobile one 15-40.oil is really black for 15 hours on it in my opinion. Is it obvious that my stock oil color wasnt doing the job ? What else could have caused this.no water or fuel in the oil that i can tell

many reasons... tight clearances and bad machining, lack of oil flow, too high of oil temps, wrong bypass in block or adaptor.... what oil filter?

the bottom had 50 hrs on it i was told.,....But it was an origonal hp420 block so it should have had the right bypasses in it. I was running a wix filter but not the extra long one. it was the 5 inch tall one

Hmm the bypass is in filter adaptor on a 420, what oil setup you running? Any pics?

ill try to get pics up . the block could be a hp370 but it does have the bypass in the center and in the small hole i will try to get some pics up. i have the oil system that came with the engine but i wanted to run my serp belt set up from mpi so i can that oil system. it has 3/8 lines and 6 inch cooler. the other one i have is like 3/4 lines with a 8-10 inch cooler and has the p.s. cooler in it as well. i dont think either has a bypass in th filter relocator.

http://www.marineengine.com/parts/me...er-and-adaptor

this is what i used

Pic didn't show, if it's in the block its not a 420, or a MArk IV block at least..

Did you re-use the oil cooler from a blown up motor?

Not clear on cooler/ lines ..did you say you used 3/8" lines?....or the 3/4"

I used the whole oiling system from the 1998 7.4 mpi. The oil lines are pretty Small. I think 3/8. I pulled the block numbers. It's a gen v 1992 merc 370 hp. The previous motor had no issues. So not cross contamination from cooler..going forward. I think if I install the 30 psi bypass in the block and take out the other bypass in the center hole ,use the bigger cooler and lines ,and install oil temp gauge...I should be good. Does this sound right?

Not if you use an oil cooler from a blowed up motor. I don't run a bypass.

Never re-use an oil cooler period. The example you gave of how the motor was running fine and then dropped rpm and oil pressure is a classic example of re-using an oil cooler.

Chris

OK.I will use new cooler lines filter and all. Should I use any bypass valve at all?

And what's a good oil pump to buy. I won't use this one with all the crap that was in this motor. Or can they be cleaned?

I like the Melling M 77 HV. Not worth trying and hoping that you got everything out of the old one.

curious as to why not? also does the oil cooler effect oil pressure?

Bearing materials can be stuck in old cooler if you re use, you can run no bypass but I use a 30 just in case, yes it could let some bad oil past but if you have oil temps you can catch it before it actually spins the bearing in a clog situation, cheaper to fix some scoring then actually spin it...

Did you reverse the oil lines when you installed it on the new engine? If you did, it will cause exactly what you are describing. I learned this the hard way in my younger life and the new engine also had 10 hours on it. If you reverse them, no oil will flow through the cooler. Toss the existing cooler, I even tossed the all the oil lines when I did this.

Good luck, but you need to find out what caused it, so you don't repeat it.

Yepp. Happened to a guy I know on a Gen V 502 just rebuilt.

I've got a similar set up with a 502/500hp using the standard 454 Mag MPI stuff, and want to switch it out without pulling the motor if possible. There's a fair amount of room to reach under the sandwich adaptor so it should be possible to spin the OEM Merc unit off and replace it, right? The bypass valve was replaced but I'm not so sure that the one under the nipple was removed, so I'll try to reach under there and get it (Hex wrench, right?)

From what I can tell the billit relocator kits use 1/2" barbed lines with pipe threads? It also looks like the merc cooler uses flared fittings so a new larger cooler will be in the plan.

I'm trying to gather as many parts as possible to minimize downtime and hair pulling, so any tips, tricks, and warnings are appreciated.

On a side note, why would you use a 30# bypass when you want 50# of pressure? Does that mean anything over 30# is being bled off? It seems like you'd want a 50# bypass spring.

I'm just trying to understand the system.

Bypass works on pressure differential across the filter element, not total system pressure.

So if it detects <30# of resistance it opens up? If that's the case then it's all making more sense now.

Yep, basically. Also, it is relatively rare to have the additional bypass installed in the center of the filter pad. That one is used if the auxiliary oil passages for an external cooler are utilized. This is typically only seen on heavy truck applications, like a box truck or something similar. You want to leave that one out, and then either install the 30-lb bypass in the outside opening of the filter pad, or use a plug to cap it off. If you plug it, make sure you are running a high quality filter with plenty of filtering capacity.

Got it.

So that's why OEM lines were adequate for the stock pump/horsepower, but a hi volume oil pump pushing against the OEM lines will trip the bypass valve or worse, activate the dump on the pump itself. Even switching out the OEM flared lines with barbed fittings is better than nothing?

I'm gathering parts to swap out the OEM 1/2" lines from the 454mag MPI on my 502/500hp that it replaced and was wondering if anybody knows the size of the fittings on the stock oil cooler? Looking at it I'm guessing 1/2" flare?

Also what size Allen key to pull the nipple out and remove the bypass valve under that? I already have the 30# valve in the side port.

Ideally I'll replace the whole system when I pull the motor out this winter, but it's not so feasible to do in the tight bilge as it sits and would at least like to switch out the lines for now.

So far I'm going with the Hardin block adapter and -12 lines.

I believe the stock GM one is around 11#'s or so.

The GMPP one is 30#'s.

If the differential is over 11#'s on the stock one, the bypass opens and bypasses the oil.

If the differential is over 30#'s on the GMPP one, the bypass opens and bypasses the oil.

Many don't use the 30# one, and just plug it...thus no chance of the bypass opening up.

Again, we are talking filter pad oil bypass , not the oil pump psi regulator typically called a oil pump bypass.