Oil recommendations

[Take5]

Hello, Just purchased a 1990 Carver 3608 with Mercruiser 7.4 carbureted engines and a Westerbeake generator. What oils do you recommend? synthetic vs non synthetic? . They have 700hrs on them. Thanks for an input.

[Midnightsun]

On my gas engine boats I had previously including 1 which had a single 7.4 mercruiser, I used Dino oil. I rarely exceeded 50 hrs so I saw no benefit in going synthetic. That being said my preference was Rotella T4 15w 40 which is what I still use in my diesel application today. Also use it in my PWC and my Ragtop summer car.

[g36]

Another vote for shell rotella

[bud37]

QR_BBPOST Hello, Just purchased a 1990 Carver 3608 with Mercruiser 7.4 carbureted engines and a Westerbeake generator. What oils do you recommend? synthetic vs non synthetic? . They have 700hrs on them. Thanks for an input.

Would you happen to know what oil the previous owner used ? Some would say to use whatever the engine provider recommends.

I would guess that most of us have used 15w40 Rotella for everything for years, there is the 25w40 camp as well and last but not least the SAE 30 and SAE 40 straight weights depending on the engine condition and the temps the engine runs at.

A quick search of this site should reveal considerable discussion about oil.....

[Take5]

Would you recommend synthetic?

[Midnightsun]

In 1990 Mercruiser did not even offer synthetic oil, in fact they recommended against using it back then. When they finally started selling "Mercruiser" branded synthetic and semi synthetic oils they changed their mind on the recommendation. IMHO these engines are rather rudimentary and do not require nor do they benefit from synthetic oil. No reason not to use it however I honestly think it is wasting money in this application.

[denpooch]

I ditto on the 15W40 which is 'non-synthetic' as recommended by engine manufacturer. (Crusader)
My Genset uses 10W30.
It would probably be prudent to look at the user manuals for both engines and get the manufacturer's recommendation.

[waybomb]

I use Mobil1 in all my cars.
The boats get Rotella.
The race boats also gets a couple hits of a stash of the old GM EOS (ZDDP) that I happen to have a stash of.

[Viper]

Synthetic is a must for some newer engines but not in a 90's vintage. Your engine manufacturer would be recommending 25W-40, their oil of course.

[edw]

Wait a minute...are you saying that you use Rotella, an oil with additives designed for diesel engines, in your gassies? Why???

Ed