5w40 in 4 stroke outboard?

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Anyone running 5w40 in 4 stroke outboard? Thinking of getting a 4 stroke suzuki or yamaha for my jon boat. I use T6 rotella in my jeep and scooter so it would be nice to use the same oil for several applications. I duck hunt in the winter so the 5w would be good for that, but would it thin out too much in the summer heat? Im in Tennessee so it gets in the high 90s every summer and low 100s on occation.

Thanks
 
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Originally Posted By: Doog
For a marine application I would not go below a 15w40. Maybe a 10w40 but definitely not a 5w.



For my personal learning, why not a 5w ?
 
I don't see a problem using a 5w. a bit more flow when cold. boats kinda do stop and go driving like a car but the engine gets shut off when not moving so I would think a 5w would help. Unless you are taking about shear but I see a boat shearing oil less than a car for the most part.
 
It will be fine. On a jon boat, you are not putting a high horsepower engine on it. Likely a small 5-15 horse engine, right? Change the oil following manufactures recommenced change intervals and it will be a good choice for a low-power jon boat engine. A small water cooled engine like that is not going to get too hot or shear the oil out too thin following recommended oil change intervals.
 
It's fine. A bit outside the OEM recommendations, but a good all around oil and it will work great. The 5W is only when stone cold, so that's gone as the motor comes up to temp. The 40 in the T6 is a bit on the thin side of many HDEO's so more like a 35, and that's close enough
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I run Rotella 15/40 in my 50 4 stroke, but if in colder weather, I could see a the 5W as a possibility.
 
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In the four stroke Yams -( yes, even the hole shot king SHO ) the synthetic 4M is 5w-30 (mentioned) - the OEM Dino version is 10w-30 ... I used them both before switching to Royal Purple HPM in 10w-30 ... RP also comes in 10w-40 ...
Boat test dot com has an interesting video on the RP marine oil ...
 
Thanks gentlemen, I don't even have the motor yet. I duck hunt in the winter so that's why I thought 5w would be good. It gets down to around 5 degrees during January.
 
Might want to visit www.nmma.org - this group feels strongly that marine oil is best even in four strokes - high RPM use
(anti foaming) - stress - not the same temps to cook out moisture - etc ...
To each their own - but for the little bit I use per year - marine grade oil ...
 
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