My Dad purchased a boat in 2016 from a marina we have used and trusted for over 20 years. But this last experience has been nothing but problems.
The boat is a 1988 Searay Sundancer 268 and has twin Mercruiser 3.0 motors. We have only ever had issues with the port side motor, the motor from day one has never lasted more than a few hours before it loses power and blows the head gasket. Finally after the 5th motor swap the marinas owner decided he wasn’t going to fix it anymore and kicked my dad out of the marina. He accused him of advancing the timing so we could slow the boat down and troll with the main motor even tho we have a kicker installed.
So with the current motor which as far as I can tell is a 1991 3.0 in-line 4. I’m assuming this because the serial number is nowhere to be found (sticker on the valve cover is worn out, and the tag above the starter is missing. The block is code comes back as a 1991, but I am unsure of the year of the head (outdrive serial number on the cover comes back as 1988)
So going by the 1991 motor or 1988 head it should have MR43t plugs in it, but it has MR43LTS.
So onto the problem, the motor sound like a can of marbles from what I believe is spark knock. We took the boat to a licensed merc mechanic and he upgraded the motor to a pertronix electronic ignition and adjusted the timing. The motor runs fine on muffs but once under load it sounds like crap. Before it would start making the marbles in a can noise and lose power then boom the head gasket would blow.
The spark plugs are carboned up badly, so maybe pre-ignition caused by the buildup. Or incorrect plugs (should have MR43T by its year range 89-91)
The fuel is fresh, and filters have been changed.
I dont know what the mechanic set the timing at but he is known for good work and is experienced with these motors.
We also checked the exhaust flappers and they are intact but we are replacing those anyways. No restrictions are visible.
So the quick version is spark knock under load, loses power and blows head gasket. Heads and blocks have been swapped 5 times with fresh rebuilt motors. Bad carbon on the plugs (rich?) but spark knock (lean/timing/fuel supply issue?)
The boat is a 1988 Searay Sundancer 268 and has twin Mercruiser 3.0 motors. We have only ever had issues with the port side motor, the motor from day one has never lasted more than a few hours before it loses power and blows the head gasket. Finally after the 5th motor swap the marinas owner decided he wasn’t going to fix it anymore and kicked my dad out of the marina. He accused him of advancing the timing so we could slow the boat down and troll with the main motor even tho we have a kicker installed.
So with the current motor which as far as I can tell is a 1991 3.0 in-line 4. I’m assuming this because the serial number is nowhere to be found (sticker on the valve cover is worn out, and the tag above the starter is missing. The block is code comes back as a 1991, but I am unsure of the year of the head (outdrive serial number on the cover comes back as 1988)
So going by the 1991 motor or 1988 head it should have MR43t plugs in it, but it has MR43LTS.
So onto the problem, the motor sound like a can of marbles from what I believe is spark knock. We took the boat to a licensed merc mechanic and he upgraded the motor to a pertronix electronic ignition and adjusted the timing. The motor runs fine on muffs but once under load it sounds like crap. Before it would start making the marbles in a can noise and lose power then boom the head gasket would blow.
The spark plugs are carboned up badly, so maybe pre-ignition caused by the buildup. Or incorrect plugs (should have MR43T by its year range 89-91)
The fuel is fresh, and filters have been changed.
I dont know what the mechanic set the timing at but he is known for good work and is experienced with these motors.
We also checked the exhaust flappers and they are intact but we are replacing those anyways. No restrictions are visible.
So the quick version is spark knock under load, loses power and blows head gasket. Heads and blocks have been swapped 5 times with fresh rebuilt motors. Bad carbon on the plugs (rich?) but spark knock (lean/timing/fuel supply issue?)
