Proper Oil Weight Question

[Oklahoma Breakdown]

So I am doing my own oil changes starting this year. I do not have a manual and the site doesnt provide one for my old boat so does anyone know the OEM reccomended weight and brand for the 5.7 liter Mercury 350?

[TeamAllen]

I use straight 40W, but here is a link to Mercruiser"s diagram.

http://www.mercurymarine.com/service...qs/fueloil.php

[Oklahoma Breakdown]

I use straight 40W, but here is a link to Mercruiser"s diagram.

http://www.mercurymarine.com/service...qs/fueloil.php

Thanks Mike, I bought 10W-40 but then thought I should double check with the experts.

[2whlin]

I have a 2001 21i with the Mercury Mercruiser 350 MAG MPI. I called Tige and a local dealer and neither of them said there was a problem with running a straight 10W-30. I just changed my oil and used Pensoil 10W-30.
Why 40w?

[Oklahoma Breakdown]

I have a 2001 21i with the Mercury Mercruiser 350 MAG MPI. I called Tige and a local dealer and neither of them said there was a problem with running a straight 10W-30. I just changed my oil and used Pensoil 10W-30.
Why 40w?

Well at the time i bought it the guys at the shop were like "umm that should do the trick" I am going to do the change this evening but think I will go back and exchange for 10W-30.

[2whlin]

I don't think it matters. As long as you have the proper amount and change it regularly. Something I did notice when I changed the oil. When checking the oil on the dipstick it still looked clean but when I drained and pulled the oil filter it was darker than what it looked like on the dipstick. Maybe it was that way, just an observation.

[2whlin]

looks like I'll be draining the oil. Just got off the phone wih Mercury and they said a STRAIGHT WEIGHT 30w or 40w (depending on outside temps) could be used, not a multi viscosity oil like a 10w-30. Their reccomendation is the Mercury 25w-40 oil.

[2whlin]

good luck finding a straight weight oil. Rotella sells it, but it's no cheaper than the Mercury product.

[Oklahoma Breakdown]

good luck finding a straight weight oil. Rotella sells it, but it's no cheaper than the Mercury product.

Thanks for ruining my day. I was going to blissfully pour the incorrect oil in. Now I am going to pay the dealer for his evil branded oil.

[Timmy!]

You can find straight weight, my local walmart had Valvoline 30 and 40 when I was there the other day and it was like $13.97 for a 5 quart jug as I recall.

[2whlin]

I'll have to go look. So who's been running these multi-viscosity oils (10w-30 and 10w-40) in their boats for years and years and have never had a problem?

[lightning59]

mercruiser 25-40 in my 350 Mag MPI, FWIW

[Timmy!]

I have 10w-40 in my boat from last season, changing it this weekend finally. Just make sure you let your engine warm up good before you get on it and you'll be fine. This has never been a problem for me since it takes a good 10-15 minutes for the truck driver to park and get back to the boat before we leave the no-wake area.

[teachercop]

I have a slightly different take...
I have always done my oil changes since day one. Usually use a MerCruiser, Quicksilver type oil filter although I have used a Mobil 1 from time to time depending on convenience. I have used Mobil 1 synthetic either 10w/40 or 20w/50 for 10 years and almost 700 hours. Had several conversations with MerCruiser and other manufacturers as boat maintenance is an interest of mine. MerCruiser 315MPI. Maybe I should change my oil selection....

[ajholt7]

Amsoil 10w-40 marine. It maybe overkill or a scam but, it always looks like new when I change it.