My project for this summer is this 1968 Mercury 650. It needs a few things, but I think I am well on my way to having a great motor. When purchased, it started well on muffs and sounded real good. Under load, in the lake, it lacks power. Takes quite a while to get up to speed.
Got a book and studied it, and started troubleshooting. Compression is good on top three cylinders... about 110 pounds... can't measure the 4th cylinder because my compression gauge just won't get in the cramped space. Put my thumb over the hole and can feel some compression there.
Removed lower unit and checked impeller. Looks new. Tell Tale hole spurts water now that I've unblocked it using compressed air.
Replaced a fuel line that looked worn. Cleaned fuel filters, some dirt was removed from the lower fuel filter. Previous owner tells me the carbs were just rebuilt professionally, so I haven't touched them. I did put in a new diaphragm in the fuel pump as the old one looked stretched.
Removed the distributor and dis-assembled. Found the top bearing to be destroyed and lower bearing near seized. Replaced bearings and cleaned up. Checked spark plug wires with an ohmmeter and found one to be flaky. Replaced Spark Plugs and built a new set of wires with parts from Sierra. Running on the muffs, timing at idle is about 3 degrees. Set the carbs at 1.5 turns out and it idles good.
Back out on the lake, it dies upon acceleration. If I set the carbs too rich (2 1/4 turns out) it accelerates ok, but idles rough.
I don't have a tach to measure WOT rpm, but it sounds about right.
So my question is, what do I do next? Pull out and clean the carbs, or am I missing something?
Any and all help is greatly appreciated.
Thanks, Cay
Got a book and studied it, and started troubleshooting. Compression is good on top three cylinders... about 110 pounds... can't measure the 4th cylinder because my compression gauge just won't get in the cramped space. Put my thumb over the hole and can feel some compression there.
Removed lower unit and checked impeller. Looks new. Tell Tale hole spurts water now that I've unblocked it using compressed air.
Replaced a fuel line that looked worn. Cleaned fuel filters, some dirt was removed from the lower fuel filter. Previous owner tells me the carbs were just rebuilt professionally, so I haven't touched them. I did put in a new diaphragm in the fuel pump as the old one looked stretched.
Removed the distributor and dis-assembled. Found the top bearing to be destroyed and lower bearing near seized. Replaced bearings and cleaned up. Checked spark plug wires with an ohmmeter and found one to be flaky. Replaced Spark Plugs and built a new set of wires with parts from Sierra. Running on the muffs, timing at idle is about 3 degrees. Set the carbs at 1.5 turns out and it idles good.
Back out on the lake, it dies upon acceleration. If I set the carbs too rich (2 1/4 turns out) it accelerates ok, but idles rough.
I don't have a tach to measure WOT rpm, but it sounds about right.
So my question is, what do I do next? Pull out and clean the carbs, or am I missing something?
Any and all help is greatly appreciated.
Thanks, Cay