Oil Recommendation for 454 Mercruiser.

C

chetcpo

New Member
Mar 14, 2015
11
WV
Boat Info
1997 240 Overnighter
Engines
454 Mercruiser
Hi everyone. I recently purchased a used 1997 Sea Ray 240 with the Mercruiser 454 engine. It has 330 hours on it and I was told by the PO that the oil was just changed.

I noticed that the oil pressure never got above 40 when running the boat at cruising speed. That seems low to me.:huh: Maybe not?

I was wondering what oil to run. Should I stick to the Quicksilver stuff or try something heavier from Volvo or another manufacturer?

Thanks
 
I was told on this site to go to bjs abd get a case of Rotella 15-40. 86$ for 6 gallons. Yea I know it's diesel oil and I brought it up to them but alot of people stood by it abd alot of people here us it. I tried it for a season on my mains and generator and after 120 hours it was still very clean. Seemed to do very well. Also it has a bunch of additives that help out your motors. More people will c him in. Also if u have factory gauges don't believe them they could and probably are a little off. Mine really never get passed 40 either
 
I stick with the Mercruiser 25w40 Synthetic Blend, but my manual (1999 Merc 4.3) recommends in this order:

1. Mercruiser 25w40
2. Straight 30w or 40w based on primary operating temperature.
3. High quality 20w40

Walmart usually carries the Mercruiser oil and a few other items.
 
I use Mobile One straight 30w and change at end of each season. Oil is always clean at end of season. My oil pres. gauge bounces back and forth between 40-60 lbs, but have never had any problems with the engine temps or any sign the oil pressure is low.
 
Use what the maintenance manual says to use. I have 2300 hours on twin 454, they use less than 1/2 liter every 100 hours. My book says use 40 weight oil strait grade. Seems to work fine.
I got the boat with 650 hours on it and have been using the same weight oil ever since. The Shell product was the best so far. Engines did not use any oil with it. It is hard to find in Canada.
 
What oil you use depends on whether the engine has the old style flat tappet camshaft or the newer roller camshaft. The old flat tappet camshaft requires a motor oil with zinc additives that protect the cam and lifters from the very high pressure between those two components. I use Valvoline racing oil 30w because it is made with the correct amount of zinc additives to protect the flat tappet camshafts in my newly rebuilt motors. As far as oil pressure goes I would not believe what the electric dash gauge reads unless it were checked first with a direct read mechanical gauge. I bought one from Harbor Freight for $15-$20.
 
Another +1 for Rotella. Diesel engines are under far more stress than gas engines. I used Merc oil while the engines were in warranty for ease of claim if necessary. Now, Rotella.

I know anal retentive boaters who have been using it for ten years plus in their 454's. No issues to date.
 
hottoddie said:
What oil you use depends on whether the engine has the old style flat tappet camshaft or the newer roller camshaft. The old flat tappet camshaft requires a motor oil with zinc additives that protect the cam and lifters from the very high pressure between those two components. I use Valvoline racing oil 30w because it is made with the correct amount of zinc additives to protect the flat tappet camshafts in my newly rebuilt motors. As far as oil pressure goes I would not believe what the electric dash gauge reads unless it were checked first with a direct read mechanical gauge. I bought one from Harbor Freight for $15-$20.
Click to expand...

installed where and how?
 
Thanks for the feedback everyone. OK if I go the Rotella route is the T6 Synthetic any better than the normal Rotella T? I'm a big believer in the superiority of synthetic oils.
 
hottoddie said:
What oil you use depends on whether the engine has the old style flat tappet camshaft or the newer roller camshaft. The old flat tappet camshaft requires a motor oil with zinc additives that protect the cam and lifters from the very high pressure between those two components. I use Valvoline racing oil 30w because it is made with the correct amount of zinc additives to protect the flat tappet camshafts in my newly rebuilt motors. As far as oil pressure goes I would not believe what the electric dash gauge reads unless it were checked first with a direct read mechanical gauge. I bought one from Harbor Freight for $15-$20.
Click to expand...
How do I know which I have? The boat is a 1997 model. Is there a way to tell short of pulling the valve covers?
 
I would suggest the 15w40 over the T6 5w40. The 15w40 is more sheer stable since it uses less viscosity modifiers. There is no reason to run a straight weight oil today. In the 1980-1990's when technology didn't provide for a sheer stable multi weight, sure, but not today. That is old school, but not necessarily the good old school.
Low pour points and extended drains are the main reasons for synthetic oils in cars. Those benefits don't hold true for boating most times. Your boat will tend to have high fuel dilution, and tend to sheer oils. You want a sheer stable oil, with a stout additive package, rated for gasoline engines. That is the description of all the major 15w40 oils made today, like Rotella, Delo, Delvac and Valvoline premium blue. Any of those would be great choices. You can stick to the Merc 25w40, but I have personal experience where it sheered to a 20w after 50 hours of use. Not a particularly good oil imho.
 
Depends on the cost differential. Normal boating at 100 hours per season/oil change, you are better off with Dino oil. The cost differential won't be made up with fuel or other savings.
 
dpmulvey said:
installed where and how?
Click to expand...


If you are asking where to install the mechanical gauge, you first remove the OP sending unit from the block and screw in the mechanical gauge. Then run the engine thru idle up to about 3000 rpm to see how it compares to what the electrical gauge was reading. If different the problem is usually the sending unit.
 
chetcpo said:
How do I know which I have? The boat is a 1997 model. Is there a way to tell short of pulling the valve covers?
Click to expand...


The changeover from flat tappet to roller tappets was the mid 90's. The Mercruiser Mags Horizons were included but not sure if any others were. You could take the engine serial # and ask your local Mercruiser dealer to confirm.
 
hello !

i always ran semisynthetic 10W-40 on my boatengines and never had an issue with that.

in fact your engine will run with whatver oil you put in , and in fact every today oil outperforms the best brand available in the days when the engine was designed.

putting in a high end thin fully synthetic will result in lower overall oil pressures but that is good and not bad because here the oil fully protects and lubricates the engine using only a thin oilfilm , with reduced pumping losses ( so lower oil pressure ) and quickly building up an oilfilm on a cold start - exactly what it is designed for.

so from a lubricating point of view your engine will run happy as hell with a 0W-30

but doing this in an "old" engine might result in higher oil consuption and small oil leaks because the piston rings and the gaskets were not designed with such tight tolerances to cope with a fully synthetic very thin highend oil.

best
 
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