Switching Oil on 1986 Crusaders

I

imspacemancraig

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I have 1986 Crusaders model 270's (350's). I have been using straight SAE 30 oil since I bought it (7 years ago). Its also what the 1986 manual says to uses and I know the previous owners did the same.

I would like to switch to synthetic oil. Being older engines I know I can get better performance and cooling properties from the synthetics now. So the question is, which type?

On Crusader's site, they say to use 15w-40 for the summer climate I boat in. But I would assume that's for the newer engines they make. Would be reasonable to assume the same carries over to my 1986's?

I know that using the SAE30 I use now, I get the correct pressure when cold. Once warmed up, when under load its lower, but not as low as when at idle. Its not dangerously low, but I figured with the synthetic formulated to change when its warmed up, I could stabilize the pressures and most likely cool/lubricate better.
 
Oil opinions are too abundant. But here is something to know about synthetics. It will flow the same when it is cold as when it is hot. I'll bet a dollar you won't see higher pressures on start up, they will be the same cold and hot.
I'll leave all the oil opinions to the experts on here.
I'll bet you another do$$ar that nobody can attribute an engine failure to changing oil brands, viscosity's, synthetics or non. That is, other than a really stupid decision like using straight 40 weight in Alaska
 
I thought they only made a difference if you started with synthetic when the engines were spankin' new and stayed with synthetic.
 
quote:
Originally posted by imspacemancraig

I have 1986 Crusaders model 270's (350's). I have been using straight SAE 30 oil since I bought it (7 years ago). Its also what the 1986 manual says to uses and I know the previous owners did the same. ....

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I agree with bobalong.

A couple of things come to mind.

-- You have 18 year old engines that have been maintained correctly for 18 years and are running as an 18 year old engine should be expected to run, why try to fix what ain't broke.

-- Are you sure the gauges are reading correctly?

If you feel the need to change oils, try Rotella T1 30 weight.
 
My last two boats have been newer with Mercruisers and I have used the Mercruiser Oil, using their synthetic blend in my 4.3 now. The old boat we had (1979 Correct Craft with a Pleasurecraft 302) a straight 40w was recommended, I used Valvoline. Boat had 2000hrs on it when I sold it, ran great, heck it might still be running. If it were me, I would not change from the recommended 30w you have been running, as long as you can find something suitable, there really is no reason to. If you DO feel the need, I would give Cruisader a call and discuss before switching.
 
Boatbum you are correct on that. There was a topic on this years ago when George was still around and it became a waste of money after x numbers of hours (very short time) on the engine. Start with it or forget about it. Save the money for fuel or cold beverages.
 
If your engine is as old and tired as you seem to think, I would not go to synthetic. If you want to go to multi-vis, get something like 25/40 or 25/50 diesel. and do a longer warm-up.
 
Well, you all make good arguments... guess I stick with what has been working. Been running well so far, why try and change up. For what its worth, I went to NAPA to pick up filters and oil (got the regular SAE30) and the guy told me the NAPA brand oil is actually rebranded Valvoline, but almost 2 bucks a quart cheaper. So back to what i was using...
 
One thing you may want to consider, being your engine is the old flat tappet design. Get some Zinc additive. I use ZDDP. My engine is a 1972. Oil companies have been removing the Zinc from oils since the mid 80's to comply with clean air requirements. Present oil formulations have very low Zinc and Phosphorous. The development and general use of roller cams allowed the lower Zinc/Phosphate formulas.
 
I'd stick with the straight 30. It's normal for oil pressure readings to be lower when the engine warms up. I've used both straight 30, and the Merc 25/40 in my '88 4.3 and its has pretty much the same readings. Cold idle about 40 psi, hot idle about 30, the lowest it has ever been is about 20 psi right after coming off plane.
As far as oil choices, Pennzoil makes a straight weight Marine engine oil that is for gas inboards.
 
I believe according to Crusader specs 10 psi at idle and 30-50psi at 200RPM provides sufficient lubrication for the older engines.

Newer Vortec's spec 10 psi at idle and 25-60psi at 2000 rpm.

The manuals for the newer, higher-revving Vortec Crusaders also says they don't recommend use of synthetic oils as they feel the synthetics do not provide enough benefit to warrant their use and added cost. And if used, normal spec'd oil change schedule (ea. 50 hrs!) should not be extended. That's a little surprising since I believe some other mfgr's are endorsing synthetics now. .
 
quote:
Originally posted by jtybt15

One thing you may want to consider, being your engine is the old flat tappet design. Get some Zinc additive. I use ZDDP. My engine is a 1972. Oil companies have been removing the Zinc from oils since the mid 80's to comply with clean air requirements. Present oil formulations have very low Zinc and Phosphorous. The development and general use of roller cams allowed the lower Zinc/Phosphate formulas.

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Good point.
 
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