Oil Additive to prevent sludge build up??

[Biggyniner]

Hey all,

Normally I shy away from additives, especially for oil, as regular oil changes tend to eliminate sludge build up. However I know boats tend to have build up on the bottom of the pan, since they are not drained from the bottom, generally. My new 350 is about together and I will soon be dropping it in the boat. Does anyone have any experience with any additives that would help prevent that layer of sludge from forming on the bottom? I would like to do as much as I can since this is a new engine, to prevent that build up over time.

would adding Marvel Mystery oil every change help? Some sea-foam like 50 hours before an oil change?? Thoughts??

Thanks

 

[achris]

MM oil= snake oil. It does nothing. And yes I know that lots of it is sold. That just proves how good the marketing department is and how gullible people are...

The best oil to use to help prevent sludge would be one with a high detergent content, like BP Corse +.

Chris...

 

[harringtondav]

This is purely opinion, but I consider oil additives snake oil. If you use high quality oil and change it annually, while it's hot, you'll be fine. You can purchase an adapter that connects a hose to the drain plug if you want to be extra careful. I had one once, but it leaked enough to goo up my bilge, so I removed it. Syn oils are super clean, but I haven't found a syn 25W-40 as Merc. specs. Since I boat w/in Merc's temp chart, I use a 20W-50 syn. 23 yrs. and no oil consumption.

 

[Alumarine]

Tore the 3.0 motor down in our 1974 glastron after 38 years of use.
It had zero sludge anywhere.
Took my 3.0 apart last winter after 22 years of use and again, zero sludge anywhere.

 

[Scott Danforth]

if you have sludge, you were running S#!T oil and not changing on a regular basis

on a well maintained engine, you will not get any sludge in the oil

the only additives you need come in the oil from the refinery.

since you do not state what motor you have - flat tappet, roller, etc. cant even start to recommend an oil

however any good quality brand of oil that is recommended for your motor and changed every year or sooner will keep it sludge free.

 

[Lou C]

The best things you can do to avoid sludge build up are regular oil changes and make sure that your thermostat functions properly to keep the engine at proper operating temp. Sticky thermostats which do not close all the way, will cause cold running (like 100-120*) and that will contribute to sludge build up. I have a 30 year old raw water cooled OMC/4.3 V6, owned it 17 years. Its gotten yearly oil changes and whenever the stat starting sticking, I replaced it, usually runs at 160-175*

When I took the engine apart in '17 to replace the head gaskets and install re-man heads there was no sign of sludge anywhere other than the milky oil from the blown HGs. On the OMC, the dipstick tube goes all the way to the bottom of the pan, same system Volvo Penta later adopted on some of their models. Not sure if the Merc dipstick tube is set up the same way. When I do the oil change, I use a vacuum pump with a garden hose adapter on the top of the dipstick tube. It works very well and you can hear it sucking air at the end of the oil change. I used straight weight Delo 30 or 40 the first few years then switched to the Merc/Quicksilver conventional 25/40. If I look under the valve covers it looks like a new engine, I don't think any additives are needed, just regular oil changes and a properly functioning thermostat.

 

[Biggyniner]

Thanks for all the tips. I will stick with regular oil changes and call it good. The 305 I tore down did have sludge so who knows what the history was with it...