02 rinker 242 fiesta vee with 5.7 Mercruiser
cvmamarty
Member Posts: 23 ✭✭
Hello am new to this site. would like some info on what type of oil to use on my 5.7 engine i have had the boat a yr and i want to change the oil on it but i don't know what type or weight of oil to use any info will be helpful.
Comments
Mercuiser 25w 40 oil is recommended however engines with 500 plus hours would do better with a little thinner oil. I have 650 hours on my 5.7 and use 15w 40 rotellaT.
your engine lacks catalysts, which means zinc and phosphorus slipping past the (likely well seated ) rings, and/or the positive crankcase ventilation pushing oil into the induction path, both from the effects of blow-by, won't have any seriously detrimental (read: $expensive$) affect to long term operation. Zinc and phosphorus protect hard parts, and allow the oil to cling to them while sitting long periods..
rust is your enemy internally... boat engines are susceptible because they often go long periods without being ran, and are near sources which promote condensation more readily... rust inhibitors drip off- unless you plan for that... most oils intended for auto's lack the rust inhibitor compounds of marine specific oil...
your engine runs in an environment more suitable for a diesel than a gasser- which is to say constant RPM's in at least the top third of the engines designed range and a steady load... diesels weigh way too much to use in smaller applications and have to be torque ratio reduced/translated to horsepower, which requires more gear box (translate, more weight).. high constant RPM's make demand for oil's that can withstand the purpose- such that racing oil would be best suited...... but still you need the other compounds, too.. but you can't be playing chemist and mixing your own cocktails.. some oils don't play nicely with others, and the last thing you need is separation under load at high RPM.
In another thread, I suggested the best oils 'for me' are these, in descending order... yours are going to differ based on ambient temperature, time/engine hours between swaps, and the advice from an oil analysis that I keep harping on here..
- Amsoil Dominator 15w50... racing oil.. made for high RPM's under extended periods and has superior shear strength.
- Amsoil Z-Rod 10w50... classic auto racing oil.. made for HP engines that sit unused for long periods between runs.. high shear strength and lots of rust inhibitor compounds...
- Valvoline 4T motorcycle oil in 20w50 full syn.. don't laugh.. the same compounds that apply and stick to the wet clutch system and lubricate the rotational assembly in the same volume will treat a marine engine kindly, too.. it is designed for silly high RPM's that our engines will never see..
- Merc Marine 25w40
- Rotella T6 5w40
- Mobile One 4T 10w40
all that said, start with the analysis...
"AMSOIL Formula 4-Stroke Marine Synthetic 10W-40 Motor Oil (WCF) is recommended for gasoline fueled four-stroke outboard, inboard, inboard/outboard (I/O) and personal watercraft motors. AMSOIL WCF motor oil is recommended for the following applications whenever an SAE 10W-40, 15W-40, 25W-40 or straight SAE 40 oil is called for: Note: AMSOIL Formula 4-Stroke Marine Synthetic 10W-40 is recommended for use in place of 25W-40 as specified by Mercury. "
Most of you insight above seems very reasonable and even spot on (and maybe I misread this part) but It'd be my experience that unlike a car on cruise control very few marine engines are under "constant" load unless they are cruising long distances on very smooth waters or trolling. When cruising I rarely see idyllic seas and imagine that as a boat runs through waves or a swell it creates fairly rapid but odd cyclical loads that strain boat engines in a very unique way. The NMMA rating for marine oils would seem to account for that odd work load along with the abusive marine environment that a boat engine has to endure.
Thanks for mentioning the oil analysis. I haven't gotten a sample yet but as soon as the incessant rain lets up it'll be oil change time and I'll be curious to get it sent in.
Just a thought. Mike
For the past two weeks my floater hasn't budged.. the rain/storms are ridiculous right now.. that Marine grade Amsoil doesn't impress as much as the Z-Rod or Dominator does for 'sitting' engines.. especially the Z-Rod.. The Z-Rod doesn't impress as much as the Dominator for high rev (peeling/sheer) protection.... the two are so dang close, though, that they are tied out for number one..
the marine would likely be #1 if I had it accessible as readily, but then again, I don't use my boat as much as you guys likely do (engine time to each day of use ratio, if you can follow that), and I won't be putting the hours on mine like you guys do- I've been out on it seven times since I got it, and I think I've put a little over two engine hours on it, as an example..
the Marine grade shines in marine engines that run a lot more than that, and (this is KEY) reach oil temperatures hot enough to burn off any and all h20... so, what I need is an oil that displaces water molecules instead, and refrains the water from mixing and becoming inseparable... So long as I can check it after and before every use, and swap it as needed if I discover anything funky going on, I'm better served with the 'sitting' oil than the Marine... or, so goes my theory that I'm willing to put to test. :-)
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As far as 'load' goes, this is my figurin'/hypothesis, so take it fwiw:
Marine engines differ from Auto engines in that they have more material on them.. they are more akin to a diesel engine block, though the geometry remains that of gassers.. they are required to push high RPM's for extended intervals, and hold steady- you don't fluctuate the boat throttle near as much as you do an auto.. they are built for balance near the top end, and built to displace heat more evenly.. the water jackets are less restrictive and wider..
the load on a marine engine is more constant, as what can be observed using the best tool available- yern good ol' vacuum gauge.. the induction, the fuel curve, the valves in the heads both intake and exhaust, and the most important of all of them- the camshaft of a marine engine, are ALL built for a specific range of use, and dial in at a narrow RPM range (maybe 600~800RPM)..
Of all the engines I've ever built, I can never recall building but one similar to a marine engine, but only mildly similar: an engine intended for stationary generator under a literal known electrical load and expected steady RPM of (iirc) 3kRPM.. everything about that engine was built for that RPM- it was a dog getting there, and I don't think it would have been prudent to rev it to it's defuel of 4500rpm because of balance issues, but you could fire it, warm it, run it up to set speed, and toss the load in it's entirety on it and it would dip only about maybe 300RPM before it caught up... it would struggle climbing back to the 3k plane, but it would, and it wouldn't budge.. you could set your watch on it's fuel gauge.. you drained the oil after 300hours of use, and duplicate the previous oil analysis.. it was predictable.
the boat, by my reckoning now mind you, has about three 'planes' (pardon the use of the word 'plane', I don't mean it as a hull planes, but as a RPM range)... there is the no wake 'plane', the cruising on plane 'plane'.. and the WOT plane.. the difference between running WOT and cruising plane isn't that much.. the difference from no wake plane to either is substantial.. the engine, though, has much more load on it when it is under it's designed (camshaft) RPM range and plowing the bow like a draught.. it seems counter intuitive, but it's truth: there is a lot of demand on an engine at idle or just above to push through the water at a range where it's simply not designed to produce the ponies.. water doesn't move through it as fast as it is needed, oil (mechanical pumps) doesn't flow as much.. the resistance on the screw taxes the engine to produce what it can barely muster and may or may not have the ability to lube/cool... (can be addressed by swapping props, just like a R&P can be swapped on a vehicle).. the need for a suitable oil for this range is more important, by my figuring that the WOT or Cruising 'planes'- unless, that is, you spend more time at or above plane.. that comes back to 'right oil for me', though..
load is difficult to explain for me.. what I mean varies from textbook definitions.. if you run an engine to a set speed using RPM cruise set, it locks in on that engine speed... do this while watching the duty cycle and counting lambdas of the o2 sensors- you will see fuel usage vary greatly... even though the engine maintains it's revs, lambda crosses zero many many times- meaning it runs rich and then lean and back and forth.. the engine is still maintaining RPM's you asked it to, but the fuel usage varies because the demand varies too.. do the same thing with a exhaust temperature cruise set.. set it to 450* and watch the RPMs vary wildly- it may be able to produce a lot of RPMs when there is lessor resistance (say, a following sea or current), but the temp climbs rapidly when the obstacles present themselves (moving into the wind or current)- because of which the RPM has to decrease to stay under the set 450*, and you slow way down....
load is hard to quantify accurately on these things because they are pleasure boats, and you just want them to gogo.. and stopstop.. if you purchased a commercial tug, though, you'd likely find more tools to manage the engines, and use the gauges to determine the sweetest spot based on conditions you could find to increase your bottom line (fuel usage, and longevity expectant ranges)...
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because I 'think' I've identified the ranges I will see most often, and expect the load to maintain consistently (relatively), have figured on where the most damage occurs (on start up) and how often that happens as opposed to expended cruising, along with the needs I have with the oil selected as opposed to it's designed intent, I'm thinking the Z-Rod or the Dominator by Amsoil is the best for my purposes, and likely better than even the Marine specific Amsoil...
sorry for the book, sir... but you asked... :-)
After you're Amsoil input on the other post, combined with the fact I'd have to order any NMMA cert full synth anyway, I ordered the Amsoil 4stroke marine full syn and it showed up 48hrs later at my doorstep. 12qts at about $8.50e should be more than enough for two changes. I'm curious about that oil analysis when I get it out.
7 times out on the water and 2hrs of runtime.....that's a drag that oil can't fix. You should need an oil change some time in the next decade.