350Q oil change

Getting ready to haul and winterize our 1975 35' Chris Craft Double Cabin with twin Marine Power 350Q engines. Engines are original with less than 3000 hours, and run strong. Any opinions about the best oil to use? The PO used a brand of racing oil that had a high zinc component.

Bilgewater said:

Getting ready to haul and winterize our 1975 35' Chris Craft Double Cabin with twin Marine Power 350Q engines. Engines are original with less than 3000 hours, and run strong. Any opinions about the best oil to use? The PO used a brand of racing oil that had a high zinc component.

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Not too long ago I bought a high-performance small block (347) engine from the builder.
While it was being run-in on the dyno I asked what oil to use in it.
They recommended Rotella T5. IMO, racing oil is meant for racing.

If the PO put most of the hrs on the motors and they're in great shape I think you have your oil recommendation.

Bilgewater said:

Getting ready to haul and winterize our 1975 35' Chris Craft Double Cabin with twin Marine Power 350Q engines. Engines are original with less than 3000 hours, and run strong. Any opinions about the best oil to use? The PO used a brand of racing oil that had a high zinc component.

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What does the manual say?

Marine Power brand original in 1975? I did not think that brand was around back then.

Chris-Craft used "Marine Power" branding from the mid '70s until the engine division was sold to Bayliner US Marine in 1983, at which point it became "US Marine Power". My engine manuals show three different version of the engine number plates for the 454s, one said "Chris-Craft", another version had "Chris-Craft Marine Power" and the third was just "Marine Power". I think they used the "Marine Power" version for the engines they sold to other builders. Hatteras and Bayliner both used Chris-Craft gasoline engines in the '70s.

As for engine oil, if I recall from the 1974 350Q manuals from my parents' former 35DC, Chris-Craft specified SAE30 as the preferable choice followed by 10W40 if multi-grade was used (check your manual for accuracy). Using something with suitable anti-wear properties for the non-roller cams is likely important.

Another option to consider is the Quicksilver 25W40 (as recommended by MerCruiser) or Rotella 15W40 T4 (as was recommended by Crusader for years).

Few things have changed more in the last 45 years than oil technology.
Probably any oil made for internal combustion engines will exceed the specs of
whatever was available in 1975.

I think it was interesting that the guys who built my high power V-8 engine used
and recommended Rotella T5, which is a semi-synthetic diesel compatible oil.

Non-synthetic Rotella T4 should do fine in any old gasser and that's what I'm putting
in my freshly rebuilt 6 cylinder engine for my 1963 Landcruiser.

So for the record:
I'm using Rotella T4 in a low compression, low revving gas engine;
I'm using Rotella T5 in a high compression, high revving gas engine; and
I'm using Rotella T6 in a VW TDI diesel engine.
You could say I'm a fan.

Expect a call from the advertising arm of Rotella any day.

Peter B said:

Expect a call from the advertising arm of Rotella any day.

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At the rate I go through the stuff I could use some free samples!

Rotella T4 and T5 are diesel rated oils. If you are going to use Rotella brand, use Rotella Gas Truck Oil instead. The additive package is designed for gas engines.

T4 is API rated for gassers too. Not sure of T5 as I don't use that.

The Shell website is most confusing. You can find documents for T4 and T6 with gas SN ratings and docs for the same oil that does not. Bottom line is read the bottle in your hand for API SN rating for gas engines. The "S" being for spark ignition.