OMC 5.8L needs 30w engine oil - noisey tappets?

[Blinking]

OMC 5.8L needs 30w engine oil - noisey tappets?

Hi all,

We did my first oil change on my current boat today (1989 Bayliner 2455 with OMC 5.8L). My SELOC service manual says I should use 30w engine oil and goes into quite a bit of detail saying that OMC recommends using a single grade engine oil (30w for UK weather temperatures).

I did a reasonable bit of searching locally and couldn't find a single grade 30w oil so after trying to work out OMC's logic I opted for a 20w50 oil which was meant for classic cars from the 60's, 70's and 80's.

My logic was that the 20w in 20w50 was closer to 30w when it's cold (closer than 15w30 or 10w40 which were the alternatives) and behaving like a 50w oil when hot (which I think OMC's logic suggests it won't get being raw UK water cooled) should be better if anything.

However...

Following the oil change, once the engine starts to warm up I can now hear what I can only guess is my tappets. The noise goes away when I rev the engine a little but returns after 5 or 10 seconds on tickover.

Now that implies to me that the oil is getting too thin to stick to the moving parts at the top of the engine when it's getting warm, but a 30w oil would be even thinner? So I'm currently presuming that it's the quality of the oil that's letting me down rather than the fact that it's 20w50 so I'm thinking I should replace it with a semi synthetic 10w30 oil.

So my question is, can anyone see the floor in my logic?

or even better,

Does anyone else have the same engine in the UK (or UK temperatures) and what oil do you use?

Many thanks!

p.s. the old oil came out like black treacle so quite possibly drowned out a whole host of noises!

 

[alb40]

Re: OMC 5.8L needs 30w engine oil - noisey tappets?

A 15w-40 grade mineral oil should be fine for you engine.

I used Castrol in a friend's Volvo V8 and it runs smooth and quiet with it.

Treacle like oil means there is something wrong with the engine somewhere. Drain the oil, flush it and re-fill with new oil plus filter, and check the oil remains fairly clean. If the oil came out like that, the the tappets had no chance of being quiet!

 

[Lakesailor]

Re: OMC 5.8L needs 30w engine oil - noisey tappets?

Have you put a synthetic or semi-synthetic oil in? This can have an effect on hydraulic tappets. On the Mazda MX5 synthetic oil makes the tappets noisy whereas semi-synthetic quietens them. Not just my observation but general opinion from U.S. forums.

The other option is that it does have noisy tappets and the prvious owner filled it with a more viscous oil to mask that.

Noisy hydraulic tappets are not a terminal condition, you'll just lose a bit of power, but not damage anything.

 

[bryan160]

Re: OMC 5.8L needs 30w engine oil - noisey tappets?

Hi, Being a qualified motor mechanic, I can only think of possible reasons off the top of my head as to why there should suddenly be a tappet noise:-

If the engine is fitted with hydraulic tappets and you have used a thicker oil (20/50) then you can lose pressure within the tappet as its to think to easily enter the tny perforations in the tappet.

If the oil engine oil was real treacly, this will slugde the engine parts such as the oil pump pick up strainer, then if you have filled it with a thick grade oil you wont get a good circulaton of oil at low engine speed, when you rev the engine the oil pump is working harder.

I would adjust the tappets (if adjustable), if not cured I would have the sump off & check out the oil pump & strainer.

Hope ths helps, Bryan

 

[Alrob]

Re: OMC 5.8L needs 30w engine oil - noisey tappets?

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I would have the sump off & check out the oil pump & strainer.


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easier said than done in a boat engine I think /forums/images/graemlins/confused.gif

 

[Remmington]

Re: OMC 5.8L needs 30w engine oil - noisey tappets?

If your selling use some fullers earth to quiet things down

 

[andy01842]

Re: OMC 5.8L needs 30w engine oil - noisey tappets?

If the old oil was that thick/black/gungey you have remove the sound proofing with the new oil so now you can hear the tappets. If the tappets are not hydraulic could be a good idea to adjust them but not with a feeler gauge. Has any one tried STP in a boat engine it works very well in other engines. I have seen neglected expire after an oil change as gunge has been dislodged and blocked oil ways!

 

[Lakesailor]

Re: OMC 5.8L needs 30w engine oil - noisey tappets?

You didn't overfill the engine with oil did you?
I have heard of overfilled engines suffering from "foamed up" oil from the crank thrashing it about.

Bit of a long shot.

Also think about worn little end bearings. They are noisy at steady, light load speeds, but quieter under load.

 

[Blinking]

Re: OMC 5.8L needs 30w engine oil - noisey tappets?

There was about 1 x litre to much in, we've now put back in the right exact amount.

The new oil was Halfords classic car oil - not sure if it is synthetic or not, assume it means its mineral based?

 

[Kawasaki]

Re: OMC 5.8L needs 30w engine oil - noisey tappets?

Stick "Straight" 30 in it.
Halfords do it.
Rock Oil do it.
Yer local bike shope should do too.
Motobrikes I mean. Classic bikes run on it.
Rock do a range of Classic oil 30 or 40 or 50.
Hydraulic tappets usually adjust themselves.

If a car wih that system stands for a while it will rattle initially then should die down.
That is, if the oil is correct and clean.
If the valves clatter all the way through the rev range summat is up.
Ie a valve prob or a tappet prob or a oil/ luby prob.
Don,t forget You are dealing with a big engine which is quite an old design.
As long as their aint no noise when She,s up to working temperature on idle.
Then the job,s a good un!

 

[Lakesailor]

Re: OMC 5.8L needs 30w engine oil - noisey tappets?

Judging from their web site it ought to be mineral based as cars of the 60s, 70s and 80s weren't designed to run on synthetics.

I'd try a flushing oil, maybe the galleries into the tappets are gummed up. It might just clear them enough.

 

[Col]

Re: OMC 5.8L needs 30w engine oil - noisey tappets?

Your engine has Hydraulic tappets and judging by the thick sludgy oil that came out it sounds like the engine was neglected. Run your engine for 20 - 30 hrs with the oil you have put in, then do another oil change. Your tappets will usually start to quieten down as they start to free off. Failing that, it's not a hard or expensive job to change the tappets. DO NOT use STP or other oil thickening agents. It only hides the problem and causes other problems.