Did compression test on my MD6A

"Hello all,

I got some unex

"Hello all,

I got some unexpected results this saturday when I did a compression test on my MD6A, and am hoping for some opinions and guidance if anyone can help. I was fully expecting one cylinder to be low.

I got 400 psi on BOTH cylinders. As I understand, the spec is 330-350 psi. Maybe that is a minimum passing spec.

Should I go back to the Fuel Pump? Timing? Pump unable to generate proper pressure?
Could the carbon/char have built up to the point that it is impairing the engine?
Do more bleeding? Change all hoses?

If you want more detail on what has been done so far in tracking down this problem, I have created a log which is below.

Thanks,
groundhog

***
Log of previous symptoms, actions, and results:

-Symptom: Engine cutting out like it was out of gas when increasing throttle beyond 15%, eventually leading to it not starting at all for more than a few seconds. Engine sounds like only one cylinder is firing.
-Action: Clean or change all fuel filters, change electric fuel pump.
-Result: Engine starts again. Can throttle up slightly more. Black smoke, engine labours, and eventual cut out on any throttle up.

-Event: Marine mechanic I met in the marina tells me that motor seems to be primarily using only one cylinder based on engine sound and uneven heat generation at top of cylinder.
-Action: Both injectors pulled and rebuilt.
-Result: Engine no longer cuts out at any speed. Boat speed goes from a dribble before injector rebuild to the speed of a quick walk (3-4 knots?) after rebuild. The boat can now actually produce a small wake. Engine sounds basically the same as beore. Used digital thermometer and the top of one cylinder lags the other by about 10-15 degrees F at start up. At 50% throttle and above, thick black smoke, RPMs or boat speed do not increase. Black charry stuff comes out of exhaust sometimes.

-Event: Run Compression test on engine. Get 400 psi on both cylinders (engine cold). Engine spec is 330-350psi?"

still has a fuel problem I&#39

still has a fuel problem I'd say. bad spray pattern from injectors. did You replace injector sleeves with injectors?

"Thanks Scott.

I had the in

"Thanks Scott.

I had the injectors rebuilt and they gave me some little soft copper washers with the new injectors. I did not install new sleeves and I did place the copper washers in the injector holes.

The boat speed is significantly improved, but it still seems to be running primarily on one cylinder due to the sound of the engine and that one cylinder head heats up faster than the other when the engine is started.

GH."

"First check Your thermostat t

"First check Your thermostat that it closes properly, and if possible do a good flush through of the cooling system. It is important that both cylinders run on equal temp. Next do a timing check of the fuel pump, the question is do You have a Bosch or CAV pump? Due to tear and wear I suspect the timing to be somewhat late."

"I have the Bosch pump.

Is

"I have the Bosch pump.

Is there info available on how to do the cooling system flush?

I guess also a fuel pump timing procedure too.
thanks,
gh"

"The Bosch is fortunately the

"The Bosch is fortunately the easy one to adjust providing You have a manual (Do it Yourself job). As for flushing the engine, the best is in fact to flush back wards through the drain plugs on the engine. Watch out so You do not fill up the exhaust system and get water into the engine. Sometimes the easiest is just to lift off the cylinder head and mechanically clean out the cooling of the block. That depends a bit on accessability (eng room space) and mechanically skills. A third way is to drain the block, fill it with a 'cleaner' and the flush. Radiator shops normally has some rather efficient stuff to use, but be careful!"