OMC Cobra 5.8L ZDDP needed?

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HorseThief

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I have a 91 Fourwinns with an OMC Cobra 5.8L (ford 351 (Cleveland?) block. Going to change the oil in the next couple weeks and wondering if anyone recommends adding STP oil additive or simmilar Zinc additive. I'm set on straight SAE 30 oil - either meijer house brand ($2.39/qt), QS (3.49/qt), or valvoline ($4.39/qt). Probably going to go with the meijer house brand due to lowest price for 6qts. I've searched around some of the boating forums but cant seem to find a straight or trustworthy answer. If anyone has any experience with or knowledge of ford 351 based OMC's please feel free to chime in. Thanks! If nothing else, would it hurt anything?
 
Nice boat, Firstly, I assume it does not have a catalytic convertors correct? If so, that opens things up to using a high zinc HDEO. Secondly, if it were mine, I would use a fully synthetic oil. Thirdly, I’m not a huge fan of high viscosity oils, but many here would suggest going to a xW40 oil weight. The verdict? Shell Rotella T6 5w40 smile If you wanted to stay with 30 weight an go down to a semi synthetic that is cheaper, how about Shell Rotella T-5 10W-30. If you wanted a conventional in a 15w40, Shell Rotella T-4 Rotella.shell.com
 
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First off, it's a Windsor, not a Cleveland, per your query there in the opener. There are plenty of marine engines based on the Ford Windsor family such as the Mercruiser 888, which was a 70's vintage 302, as well as a variety of mills from PCM, which includes the GT-40, which we have in our '95 Supra. The 351W is a very durable engine and does not have lofty oil requirements. We are running Delvac 1 ESP 5w-40 in ours, the original spec was a marine 20w-40 IIRC but most folks run an HDEO in them in 15w-40 or 5w-40. Is yours carbureted or EFI? Do you know what the output is? More information would allow us to determine whether it is roller or flat tappet. I'm not intimately familiar with OMC's spin on this engine, but I'm quite familiar with SBF's.
 
Myself I would just use plain Valvoline VR1 30 and skip the additive. This is my favorite oil for the muscle cars and race duty cars I have owned and still own, however it is scarce as hen's teeth. Yes I do realize you are running this in a boat, my recommendation still stands. My last purchase was at a Helena MT Autozone a long time ago. You can get 20w50 all day long but the straight 30 and 10w30 are impossible to find on the shelf. https://sharena21.springcm.com/Public/Do...12-ac162d889bd1
 
perfect Q for BrunoLoco. But easy - NO ADDITIVES! 25w40 mercury marine quicksilver 4 stroke oil. Or a 30 HD How hard do you run it? you open her up and run over 3500 rpm for minutes on end? Do you have an Oil temp gauge? After a hard run what is oil pressure at 1000rpm? For car guys, a marine engine is like trailer towing up a mountain. ILSAC multigrade would be shredded.
 
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For what it’s worth, I’ve been running Delo 400LE 15w-40 in mine for the last 4 oil changes, without incident. A lot of the old school Nautique fans (all Ford V8s) run Valvoline VR1 for the additive package. Nobody I know runs additional additives. As the formulas for diesel/mixed fleet oils continue to evolve, it’s hard to find Delo 400LE (defeating half the reason I used it), so now I either need to stockpile a few years of changes somehow, or switch to something else.
 
Wow, a lot of responses! - sorry I kind of spaced on the boat and this thread for a while. Only reason Im kinda set on sae 30 is because that's the gospel that is preached by every engine builder and shop in the area. With the way it's propped and loaded it gets run around 3200-3600rpm for about 12-20 mins across the bay to our cottage with a 15 minute putt down/up the river before/after respectively. To answer some other questions it is carburated and oil is usually changed seasonally - boat averages less than 30hrs a year ( like I said, it's for transportation, it's not the destination). I always see the Quicksilver 25w40 and I'm tempted to use it and I'm sure there would be no issues, but when factoring in cost (delo is much more attractive!), it's lived it's easy life on a steady diet of sae 30 thusfar with no issues. I was more concerned with lower zinc levels in modern oils and TBH, don't know enough about the 5.8l cobra/Ford 351 to know if it would benefit from a supplement. So an HD 30 would be suitable as well then? If so, then that makes things quick, easy, and cheap - which all equals more time on the water and more beer money.
 
Originally Posted By: HorseThief
Wow, a lot of responses! - sorry I kind of spaced on the boat and this thread for a while. Only reason Im kinda set on sae 30 is because that's the gospel that is preached by every engine builder and shop in the area. With the way it's propped and loaded it gets run around 3200-3600rpm for about 12-20 mins across the bay to our cottage with a 15 minute putt down/up the river before/after respectively. To answer some other questions it is carburated and oil is usually changed seasonally - boat averages less than 30hrs a year ( like I said, it's for transportation, it's not the destination). I always see the Quicksilver 25w40 and I'm tempted to use it and I'm sure there would be no issues, but when factoring in cost (delo is much more attractive!), it's lived it's easy life on a steady diet of sae 30 thusfar with no issues. I was more concerned with lower zinc levels in modern oils and TBH, don't know enough about the 5.8l cobra/Ford 351 to know if it would benefit from a supplement. So an HD 30 would be suitable as well then? If so, then that makes things quick, easy, and cheap - which all equals more time on the water and more beer money.
Honestly, I'd run a 15w-40 or the Mercury 25w-40 in it over an SAE30. Ours is 310HP, and I spin it past 4K regularly, which is perfectly normal duty for this mill. Yours doesn't appear to be a roller motor but since it doesn't spin as high, I still wouldn't be concerned. We used regular 5w-30 in our 888 and it had thousands of hours on it and we had no valvetrain issues. It topped out at about 4K, but was regularly run at 3,200-3,500RPM.
 
I understand your engine builders love SAE 30, but Volvo played that game several years ago with disastrous results, despite using an oil that was nearly a carbon copy of Amsoil SAE 30 synthetic, if not actually that oil. At 30 hour OCI, I wouldn't be awfully worried about shear. You didn't say what Four Winns. If that's a heavy boat with no oil cooler, stick to a 40 weight, at least. The issue that pops up there is viscosity thinning due to heat.
 
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