"Ok. I have a 1987 3.7 Merc &
"Ok. I have a 1987 3.7 Merc (470 block). Last year I spun a rod bearing. So I pulled it out, tore it down, had the crank turned and put it back together with new bearings. The shop said my crank was not bent. I had the rods checked (replaced 1 w/a cast piston weighed and matched to the other 3) and honed the cylinders lightly. I also blew through all of my oil galleys and washed the block with soap and water. My exhaust riser is in great shape and everything went back together with new gaskets. I had my Merc manual on the workbench next to me the whole time. The first trip out, it ran great. Had power, planed out fast, ran cool and sounded good. Was a good day.
The following weekend, I put it in the water and no more than 1 minute from the ramp, I had a rod knocking again. My temp was very low (just put it in), my oil pressure was 60 (until my rod started knocking - then dropped to 20) and hadn't even hit 2000 rpm yet. I have a new temp sender and gauge and have verified with a laser temp gun.
When I had it apart before, there was no water or fuel in the oil. My coolant level was fine. I've had the 4" heat exchanger apart and it looks great - never in salt. I know by the sound what it is. How the heck could I wipe out a rod bearing like that? This one doesn't make sense to me - looking for ideas. My boat is 19', alpha 1, and 19 pitch prop.
Wish I could find a reasonably priced 3.0 to drop in and get rid of the thing - the boat isn't worth a new engine. I don't ever want to own a 3.7 after this one
"
"Ok. I have a 1987 3.7 Merc (470 block). Last year I spun a rod bearing. So I pulled it out, tore it down, had the crank turned and put it back together with new bearings. The shop said my crank was not bent. I had the rods checked (replaced 1 w/a cast piston weighed and matched to the other 3) and honed the cylinders lightly. I also blew through all of my oil galleys and washed the block with soap and water. My exhaust riser is in great shape and everything went back together with new gaskets. I had my Merc manual on the workbench next to me the whole time. The first trip out, it ran great. Had power, planed out fast, ran cool and sounded good. Was a good day.
The following weekend, I put it in the water and no more than 1 minute from the ramp, I had a rod knocking again. My temp was very low (just put it in), my oil pressure was 60 (until my rod started knocking - then dropped to 20) and hadn't even hit 2000 rpm yet. I have a new temp sender and gauge and have verified with a laser temp gun.
When I had it apart before, there was no water or fuel in the oil. My coolant level was fine. I've had the 4" heat exchanger apart and it looks great - never in salt. I know by the sound what it is. How the heck could I wipe out a rod bearing like that? This one doesn't make sense to me - looking for ideas. My boat is 19', alpha 1, and 19 pitch prop.
Wish I could find a reasonably priced 3.0 to drop in and get rid of the thing - the boat isn't worth a new engine. I don't ever want to own a 3.7 after this one