guess the cards are always against me!

Well, the post said Performance Application. In 1983 this was high performance:

1983 Forluma 272 twin Merc 260s (350 cid).

Currently, 1520 hours. Never had the valve covers off. One motor is starting to use a little oil. Still runs great.

Good old thread TTT!

All original GenV 454 mag with 600 something hours, that I bought used. Never been apart.

Small block Chevy Merc that I bought new in 1990, 550 hours, never been apart.
When I change oil it reads all the way up to the full line. She’s still tight.

You will get all kinds of different recommendations on this, but here’s mine.

If you can, start with a motor of proven durability, some packages have a history of running forever, others a reputation for earlier failures.

Run Mobil 1 – 15W50 total synthetic…..More on this below

1) Follow the Merc break in drill with a couple of exceptions…

2) Change oil early, the first time, on a new or fresh motor, 2-5 hours, to get any metal particles or debris out of the oil. Install an oil pan magnet or magnetic drain plug now.
If you can, install the “new” drain hose through the transom kit. It allows you to get all of the old oil and trash out. If you’ve ever rebuilt many engines you’re amazed at the crap you find lying in the bottom of the pan.

3) Your second oil change at about 15-20 hours. Afterwards go to “normal” oil change intervals, 25-50 hours depending on how hard you run it, and age/health of the engine.
“Tired” engines have more blow-by, and will accumulate nasty combustion by products, in the oil, quicker.

4) Never operate your engine low on oil.

5) Never operate your engine if overheating. If she starts heading for 200, and lives are not at risk, swallow your pride and call for a tow, don’t try to make it back to the dock. The audio alarm is a good safeguard.

6) Pay close attention to your cooling system maintenance, and pull your risers every couple of years (in fresh water) to ensure you don’t have any leaks into the exhaust, or cylinders. Don’t discard the thermostat, you need to have some system to maintain consistent coolant temperatures throughout the engine.

7) Never run it hard when cold. Piston temperatures, and diameter, rise at a much quicker rate than the surrounding cylinder wall.

I have paid close attention to the synthetic debate for years, I listen to what Teague and others say very closely. I have the good fortune of living on the lake within earshot of the majority of the NASCAR engine building shops. It is sweet to hear them spinning them over 8000 on the dyno. My next door neighbor is a crew chief and I have had a chance to talk to some of the members of a couple of teams. They claim, with the same viscosity rating, there is little to no measurable difference in Horsepower output between synthetic and Dinosaur oil. They run the synthetic because it’s so much more stable across temperature ranges, providing more consistent flow and pressure, and because it will handle higher temperatures.
If you are afraid that synthetic will prevent proper and complete ring seating, you can run the Merc oil for the first 50 hours. However, most of you are probably aware that Corvette, Porsche, and others, ship their vehicles from the factory with Mobil 1 in the crankcase. And Harley Davidson now sanctions the use of total synthetic in all of their engines.

If you’re still living under a factory engine warranty run the Merc 25W40, until Merc changes their tune.

Been building motors since 74’ and have seen some noteworthy hours (or mileage) racked up. I boat in 25 to 100 degree temperatures.

I confess to being eccentric about lubrication, but so far I’ve had pretty fair results.

On the highway:

1993 Yukon – 5.7 – Tow vehicle, 392,000 miles, valve covers never removed. Still running her
1997 Tahoe – 5.7 -Tow vehicle, 208,000 miles, Still running her.

1988 Dodge Ramcharger – 5.2 – Tow vehicle, 202,000 miles, valve covers never removed. Sold.
1975 IH Scout – 342 – Tow vehicle, 242,000 miles, valve covers never removed. Sold.
1974 Trans Am – 400 – 172,000 miles, valve covers never removed. Sold.

I don’t run synthetic on the highway, except in the Harleys. Not near the load as a boat, oil doesn’t run as hot, it’s expensive, and heck, can get 2-400,000 miles without it.

I saw approximately 930 trouble free hours on my 330hp 454 before my mechanic charged me for a winterization, but failed to perform the work. I upgraded to a complete 496 Bravo 1 repower and have about 170 trouble free hours logged so far.

On the otherhand, I also have a 1994 200hp Merc OB with over 1,000 trouble free hours... only needed to rebuild the lower unit 1x and a 1986 200hp Yamaha OB with approx 570 trouble free hours.

Good post, but you lost me on the last part. Are you saying you don't use synthetic in your cars?

I have twin 260's with over 600 hours. Boat sat in storage for eight years. Only thing I have replaced are batteries, still runs great.