engine oil?

[finnlander]

what type of oil should i be using in a 1987 5.7 265 h.p.  mercuicer?  and what type in a 1973 mercuicer 250 inline 6 with 165 h.p.? are these engines catalyst or non catalyst, because this helps  determines  the type of oil.  i think i have this right...... thank you 

[borderline 350]

Dear Finnlander,

         The best oil to use is BradPenn with the high zinc additive content. Straight 30 or 40 weight is fine for these old flat tappet engines. Do not use synthetic oils for these old engines.DO NOT USE MULTIVISC' oils if you are trolling. They do not have cat/convertors etc. so no need for the synthetic oils......Respectfully submitted....EX NYS RESIDENT March 1st.........EX Jet Boat Bill.

[finnlander]

thought i would recieve a few more replies.......mmmmmmmmmmmm    someone out there must have a 5,7 mercruiser.

[Capt Vince Pierleoni]

No more replies necessary. The last gentleman that took the time to respond to you is a true EXPERT with marine engines. He has tore down and rebuilt them along lake Ontario for over 30 years. When he talks engines everyone I know listens.

It really comes down to whether or not you have a catalytic converter, and how you use the motor. The advice about zinc is sound science, and for many years SAE 30 weight has been the standard in small block marine engines, unless it is "tired", and then some bump it up to SAE 40 when the air temps warm a bit.

I've owned several sets of 5.7's/350s and the best advice I can give is watch/tune your carbs so they don't "dump" gas into your oil, and be a guage watcher and don't let them get hot--replace impellers as necessary.

We are all battling the fraud of ethanol gas, so make sure there are water separators in your fuel lines.   

[finnlander]

did not mean to say he did not know what he was talking about. i just don.t understand if the 88 5.7 and the 73 250 have cat converters. i don,t think they do, so i should be using 30 weight in both engines??? i called my local marina and they told me to use 2040 in the 5.7 andjust reg 30 in the older 250. sorry for any misunderstandings to ex jet boat bill and i was not quetioning his expertise.