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Thread: Oil viscosity for vintage jet boat engine

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    Oil viscosity for vintage jet boat engine

    My boat has a Indmar 350 jetpac engine that originally specified straight 30w motor oil. Knowing that oil technology has improved greatly in the past 40 years I donít believe thatís the best oil available for my engine. This spring when I changed the oil I used Joe Gibbs Driven xp9 synthetic 15w40 that I run in my drag car. The boat runs great and oil pressure is approx 10psi per thousand rpm. It hasnít burned a drop of oil all season. Thoughts on using this versus conventional 30w?

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    Team Dirt Bag Intern NUTTZ
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    Re: Oil viscosity for vintage jet boat engine

    Do you still have the original oil pump, pick up and pan that was original with the engine? Remember, oil temp is a very big factor in your engines life in a jet boat. The block takes a very long time to heat up and has a constant source of cold lake water to cool it. Your drag car might or might not be a different Many of us run VR 50 with zinc only because of the high rpms, higher capacity pans and high flow pumps on new old engines. Talk to your machinist before switching to much up? Boiling oil in a luke warm block is bad but cold thick oil that wont drain.....
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    Re: Oil viscosity for vintage jet boat engine

    I run Brad Penn 10w 30 with zinc in my BBO stock oil pump and stock oil cooler with a 165 degree thermostat . The motor has all forged internals, oil mods , aluminum heads etc .

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    Re: Oil viscosity for vintage jet boat engine

    This boat is sorta new to me. It was rebuilt but is mostly stock. Was bored .030, has better carb and ignition system. Assuming stock oil pump and pickup. Probably making around 320hp. Only rev it to around 4400. Itís nothing crazy as far as engines go, I just want good longevity out of it, and Iím not very nice to the boat lol. The oil I used is a very high end $20+ per qt synthetic with zinc in it. I talked to a guy at royal purple once and he told me with the new synthetic oils to run the lightest weight oil that still maintains good pressure. I know boat engine demands are way different though.

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    Re: Oil viscosity for vintage jet boat engine

    Quote Originally Posted by Jons999 View Post
    I talked to a guy at royal purple once and he told me with the new synthetic oils to run the lightest weight oil that still maintains good pressure. I know boat engine demands are way different though.
    That's basically the same advice we give people as well. Use the oil viscosity to dial in your oil pressure where you want it. One of the best ways to determine minimum weight is to do a prolonged blast to get the oil good and hot. Bring it back down to idle and make sure you still have at least 30 PSI and the pressure shoots up immediately when you rev it. Over 40 at smokin' hot idle, to me, is too much. Like I said, main thing is it shoots right up when you rev it.
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    429CV23's Avatar
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    Re: Oil viscosity for vintage jet boat engine

    I run 9qts of straight dino 10W30 plus a bottle of ZDDP or break-in additive in my 466ci BBF; I only use high quality Wix oil filters, no Fram garbage. When I killed #8 rod bearing and the rear main, the shop that cut apart the Wix filter had one heck of a time getting it open to inspect the media; took over 30min to get it apart. They said they can open a Fram in 2min.
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    Re: Oil viscosity for vintage jet boat engine

    Valvoline VR1 10w30 here in both the float and race car!
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  9. #8

    Re: Oil viscosity for vintage jet boat engine

    VR1 20-50 in both my 455 and 454.

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    Re: Oil viscosity for vintage jet boat engine

    I was doing some oil research and found out 15w-50 mobil 1 has close to the same zinc and phosphorus as vr1 20 50. At $22 a 5qt jug from walley world I'm thinking of changing this next oil change. Mobil 1 phosphorus level is 1200 ppm and zinc is 1400 ppm. Vr1 is 1300 and 1400ppm. Vr1 is impossible to find in kommiefornia.
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    Re: Oil viscosity for vintage jet boat engine

    Really? I just bought 2 cases yesterday. My local NAPA has both in stock.
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