Stormrider

I just bought a used boat...
obviously need to change oil.
I was going to use Mobil 1 15-50.
Is this good?
And for the initial change is it necessary to
do it twice in a row? to get rid of all the old oil.

fund razor

Nobody agrees on what oil to use.
You see alot of threads on the topic.
Some guys like synthetic, some don't.
Hardly anybody uses multi-weight however.

Many guys use straight 30 weight. I change my oil a couple times per summer, and it is so clear, that you need to hold the dipstick in the light to see the oil.
Plus, I put in an oil change system that has a fitting at the drain pan fitting, so you get ALL the oil.
I use straight 30 weight. If I was in your position, I would change the oil and filter after a short warm up, then change then oil and filter again after a run.

My friend uses Mobil One. He likes it. I don't think that the type of oil is as important as how clean you keep it.

That's one guy's opinion. I'm surprised that you haven't gotten more.
Good luck.

Downtown42

straight 40 at 50+degrees air temp...merc book 1993

fund razor

My 79 merc book says straight 30 at the same temp.
My 87 OMC book says SAE 30 also.
I wouldn't have any trouble with 40, but I don't think I would use 50.

97BossHammer

I agree the oil type subject has been around the ringer a time or two. I was running straight vavoline 40 in mine....but after reading a few of them, I switched to Mobile 15w 50 synthetic. I like synthetics much better....use them in the cars/trucks also. The cheapest and easiest way to change it is to buy the drain hose line, basically just replaces the oil pan bolt and has a hose for easy access and allows for draining all of the oil, unlike the pump systems that I've seen and used. I'd pick a schedule and stick to it......I change mine every 20hrs. I agree with whats posted....I don't think it really matters what oil you choose.....just be sure it's changed often, it's more of a personal preference if anything.

FunHome

Does the oil drain hose that you guy's are useing fit threw the bilge drain hole???

I'm looking at the one form Jabsco and it looks kinda big......

Hydrocruiser

www.Bobistheoilguy.com

Bottom line:

Conventioinals can take up to 250*F before turning into sludge.

Most Synthetics 400+*F

Mobil-1 20W-50 V-Twin 518*F The King of Hightemp performance syn's

Amsoil Series 2000 Severe Service 20W-50 453*F

Mobil-1 15W-50 446*F

Royal Purple 20W-50 435*F

Redline 15W-50 486*F

Cylinder walls can get up to 400+*F

Some fully synthetic oils outperform others but all fully synthetic oils outperform conventionals 2:1 when it comes to themal operating capacities and shear tolerance. It can be enough to save your engine some day is what I always say!

It's your call.