Mercruiser engine oil questions.

[CorvetteOnWater]

I have a 5.7 260 mercruiser and my service manual states to use single weight oil like 40w. Just about any oil I find is multi viscosity wether labeled boat or car.

I would really like to use Mobile 1 Gm engines generally use 5W 30 would this be ok?

 

[deves3000gt]

Re: Mercruiser engine oil questions.

I have been told buy a marine shop to use sae 30 weight. there is a post on here i saw some one had posted the difernt weight to outside temp. rating. The 30 weight was right in the middle. It is also said that you need a thicker oil do to the sustained high rpm's.

 

[havasuboatman]

Re: Mercruiser engine oil questions.

No. That is to lite. Use straight 40, or Merc. 25/40 (if you can afford it, it's pricey)
I aske Jim Fry ( Mercruiser's head instructor. west coast) why Merc. recommends straight 40 wt. but markets 25/40 and he said that because their oil meets such high standards that it can hold a straight oil standard viscosity in a multi-grade oil. Those are his words, not mine.
But you want the heavier oil because the stresses a marine engine endures are different than an automotive engine. Most notibly is the lack of the stop and go, and veriable load conditions (no hill climbing)

 

[Gary H NC]

Re: Mercruiser engine oil questions.

Use straight 30w...
Any auto parts sells the Rotella truck oil...perfect for marine use.Very good oil.
Its all i ever run in my 4.3 and never had a problem.
I did use 10w 30 one time and noticed the oil pressure was a little lower.

 

[n2ostroker]

Re: Mercruiser engine oil questions.

On older flat tappet cam motors I run Castrol 20-50 4T motorcycle oil, HD diesel 15-40, Valvoline 20-50 racing or the Mercruiser 25-40. All these still have good amounts of anti wear additives to keep from premature cam failure. I like the heavier weights as well cause of the extended high load run times. I've even seen a roller cam get scarring on the lobes with newer oils when running stiifer springs.

On my current motor I use the cheap 15w-40 diesel. Rotella and Delo have even started reducing the levels of ZDDP and phosphorus in their oils.

 

[Don S]

Re: Mercruiser engine oil questions.

Below is what Mercruiser recommends for your engine.
http://northamerica.mercurymarine.com/serviceandwarranty/mercruiserfaqs/fueloil.php
If you choose not to use what is recommended, then go for it. Just don't complain if something happens to your engine.

Just remember, oil threads in marine/boating forums are usually full of " I Use ___Fill in the blank____ oil and have never had problems.
Every type oil has been used and recommended by somebody on this forum. Doesn't make it good, just means someone used it and didn't blow up in their 10 hours of boating, but it worked great in their car.

 

[havasuboatman]

Re: Mercruiser engine oil questions.

Below is what Mercruiser recommends for your engine.
http://northamerica.mercurymarine.com/serviceandwarranty/mercruiserfaqs/fueloil.php
If you choose not to use what is recommended, then go for it. Just don't complain if something happens to your engine.

Just remember, oil threads in marine/boating forums are usually full of " I Use ___Fill in the blank____ oil and have never had problems.
Every type oil has been used and recommended by somebody on this forum. Doesn't make it good, just means someone used it and didn't blow up in their 10 hours of boating, but it worked great in their car.

Exactly

 

[Begester]

Re: Mercruiser engine oil questions.

Good point.

I'm going to be changing my oil in preparation for my de-winterizing this week. Is there anything special I need to do? The boat has been sitting since November (winterized), so do I need to worry about those first few seconds before the cylinders are fully lubricated?

I've never had an issue with low oil pressure.

 

[Begester]

Re: Mercruiser engine oil questions.

Good point.

I'm going to be changing my oil in preparation for my de-winterizing this week. Is there anything special I need to do? The boat has been sitting since November (winterized), so do I need to worry about those first few seconds before the cylinders are fully lubricated?

I've never had an issue with low oil pressure so I am assuming my oil pump works fine. Is this a correct assumption?

 

[HT32BSX115]

Re: Mercruiser engine oil questions.

It's always good to change your oil at the end of the season BEFORE winterization so that you don't have contaminated oil sitting there all winter. If you did that, just go boating and change it in SEP/OCT/NOV etc.

If you didn't, change your oil and go boating and then change it before you park it for the winter.

Cheers,

Rick

 

[boatguya1]

Re: Mercruiser engine oil questions.

No. That is to lite. Use straight 40, or Merc. 25/40 (if you can afford it, it's pricey)
I aske Jim Fry ( Mercruiser's head instructor. west coast) why Merc. recommends straight 40 wt. but markets 25/40 and he said that because their oil meets such high standards that it can hold a straight oil standard viscosity in a multi-grade oil. Those are his words, not mine.
But you want the heavier oil because the stresses a marine engine endures are different than an automotive engine. Most notibly is the lack of the stop and go, and veriable load conditions (no hill climbing)

Isn't Jim the only Merc instructor on the west coast. If you haven't been in one of his classes this year next time you go ask him about the speed of light and time travel. Great guy, if he can't answer a question he'll go to the ends of the earth (merc's earth anyway) for an answer.

James

 

[havasuboatman]

Re: Mercruiser engine oil questions.

Isn't Jim the only Merc instructor on the west coast. If you haven't been in one of his classes this year next time you go ask him about the speed of light and time travel. Great guy, if he can't answer a question he'll go to the ends of the earth (merc's earth anyway) for an answer.

James

Yep, he's the guy. What most people don't know is that almost everything in those shop manuals was authored by him. I'll ask him about the speed of light, too.