Hi Everyone,
I put a new motor in my boat this year, after doing it last year and having that one lose oil pressure by the end of the season.
It’s a 1983 mercruiser mak IV 454, 4 bolt main (370 cyclone) engine with a TR drive and BW transmission. Its stock, thunderbolt iV ignition and has an custom built 850 quadrajet
This engine runs great and has good oil pressure however I get this high pitched metal on metal sound once its warm, under load and above ~3500 rpm. It starts fine, we idle out of the no wake zone, about 10 min, then bring it up on plane, going over 3500 RPM, all is fine, then after about 1 to 2 min, I start hearing this metal on metal sound that is random, it does not follow the RPMs or seem to have any bearing on performance, if I bring it down under 3500, say 3200 it seems to go away or only happens every once in a while, if I push it a little harder, it does occour a little more frequently but not a lot. I don’t want to push this new engine over 4000 yet.
The sounds seems to be coming from the starter side toward the rear of the engine (2,4,6,8 cyl side) I pulled the starter thinking the bendix was hitting the flywheel and changed starters, no change and good clearance.
I pulled the plugs today, they only have a few hours on them but the back (cyl 8) plug was a little blue on the base ring and elecrode looked a little more heated than the others. The rest have a black base ring and the electrodes looked about the same. Base timing is 10 deg at 850RPM per the book.
Here are pics of the plugs and I was able to capture the sound on this video. There are 2 pops at 57 seconds that are loud and a few more quicker together but quieter at 59 seconds. This was at about 3700 https://www.youtube.com/watch?v=MOl4U0q98Wo&t=10s
Differences from last year: new distributer with an updated pickup, old one had the original pickup, a water pump pulley from a 350 (bigger diameter, temp on the gauge is normal, but goes up slightly once on plane) ran it with the carb and had the noise, then rebuilt it, no change. There is a slight rise and fall of RPM at idle but I have not readjusted the idle air screws yet. It was worse before I rebuilt the carb.
I also tried squirting water on the intake to see if there was a leaking intake gasket.
Thoughts on the sound and a cause?
I put a new motor in my boat this year, after doing it last year and having that one lose oil pressure by the end of the season.
It’s a 1983 mercruiser mak IV 454, 4 bolt main (370 cyclone) engine with a TR drive and BW transmission. Its stock, thunderbolt iV ignition and has an custom built 850 quadrajet
This engine runs great and has good oil pressure however I get this high pitched metal on metal sound once its warm, under load and above ~3500 rpm. It starts fine, we idle out of the no wake zone, about 10 min, then bring it up on plane, going over 3500 RPM, all is fine, then after about 1 to 2 min, I start hearing this metal on metal sound that is random, it does not follow the RPMs or seem to have any bearing on performance, if I bring it down under 3500, say 3200 it seems to go away or only happens every once in a while, if I push it a little harder, it does occour a little more frequently but not a lot. I don’t want to push this new engine over 4000 yet.
The sounds seems to be coming from the starter side toward the rear of the engine (2,4,6,8 cyl side) I pulled the starter thinking the bendix was hitting the flywheel and changed starters, no change and good clearance.
I pulled the plugs today, they only have a few hours on them but the back (cyl 8) plug was a little blue on the base ring and elecrode looked a little more heated than the others. The rest have a black base ring and the electrodes looked about the same. Base timing is 10 deg at 850RPM per the book.
Here are pics of the plugs and I was able to capture the sound on this video. There are 2 pops at 57 seconds that are loud and a few more quicker together but quieter at 59 seconds. This was at about 3700 https://www.youtube.com/watch?v=MOl4U0q98Wo&t=10s
Differences from last year: new distributer with an updated pickup, old one had the original pickup, a water pump pulley from a 350 (bigger diameter, temp on the gauge is normal, but goes up slightly once on plane) ran it with the carb and had the noise, then rebuilt it, no change. There is a slight rise and fall of RPM at idle but I have not readjusted the idle air screws yet. It was worse before I rebuilt the carb.
I also tried squirting water on the intake to see if there was a leaking intake gasket.
Thoughts on the sound and a cause?
