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?