What oil for COLD RUNNING Donzi?

[JimG]

You guys got me thinking all sorts of oil stuff now!

My 1970 Donzi 18 is powered by an original Holman Moody 351 Windsor 290hp. It uses a factory original bypass instead of a circ pump, that's fed from a Jabsco crank mount water pump. Even though I use a thermostat, (tried three so far), the engine runs very cold, around 120 degrees. (I verified the temps with an infrared...) I don't have an oil temp gauge. Apparently this is very common on this setup, as verified by several fellow owners on the Donzi forum, as well as by Alan Brown, (the general manager of Donzi when my boat was built.)

With this in mind, what oil will protect well at those temps? I've been running either HDEO 15w40's or Kendall 20w50 along with some Valvoline Synpower additive. What do you guys think?

Jim

 

[jeremiah2360]

Wow 120

Thats very low. I know as far as an auto engine goes wear rates really take off starting below about 170. I learned this reading posts about the 180 thermostat debates and came across a table of wear rates and temp. I`m no expert but Mobil 0-20 or another 0-20 synthetic seems like a must with such low temps. Maybe even adding a quart of MMO too. AEHASS(sp) would have a heart attack if he found out your running such a thick oil with those temps

Hopefully there will be more posts on this,I`m interested what others might think. Good Luck.

 

[Steve S]

What is the oil pressure? and temperature .one of the weird things was the control of engine temps. I have had a few bbc engines in my flat bottom over the years. I really think the best setup is a closed system rather than using what ever floats the boat .cause what I have been told is the cooler engine temps keeps the lake water minerals from building up as fast in the coolant passages. The engines would last a bit longer with proper operating temps and good oil filtration.

 

[JimG]

I don't have an oil temp gauge on the Donzi, so I'd only be guessing. The pressures run 60 at startup, 45-50 running, 25 idle. Absolutely normal for a raw water cooled v8. (My old Chrysler 318 in my Trojan shows exactly the same characteristics.)

These HM engines live a long time (1000+ hours) at those low temps. It's sort of strange, but I'm used to it now.

Why would you choose a 0-20w for this engine? Wouldn't that be really thin at those temps?

Jim

 

[jeremiah2360]

JIMG, I posted this link in the "Car and Truck Gas Engine Oil" section hoping for more feedback.

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=011212

 

[Ryan00TJ]

Please do not put a 20W in a hard run Marine application!!! Since this engine runs pretty low water temps and more than likely oil temps you will experience fuel and water dilution of the oil. This will quickly turn the 20W into a 10W or less. No less than a 40W.

What temp Tstat are you currently running?
I've done lotsa testing in my Hammond and found the Mercruiser 142 degree to be perfect for my lake conditions. My local lake water is now close to bathwater. If you boat in cold water resort to a 160 Tstat. I would install or try an find out your oil temps before taking any action.

With the 142 stat and warm lake water my 360ci SBC runs 145-150 water temps and 180-190 degree oil temps cruising at 2500rpms. WOT runs will increase the oil temp to 210 or so max temp. This is in conjunction with a fairly large oil cooler. HTH

 

[wileyE]

Just because the coolant temp is low doesn't mean the oil temp is too low? The coolant is constantly being replenished with cold lake water, the oil is in a closed loop. I'd say your normal oil pressure tells you your temp/visc is OK. If your real curious about the oil temp get a hold of a lazer thermostat (seen em as cheap as $30), give the boat a good run then pull the dipstick and lazer the tip of it with the oil on it.

 

[JimG]

I've tried a 140 & a 160, same results...

 

[Ryan00TJ]

I would get interested in the actual temp and install an oil temp gauge. I find myself looking at mine all the time along with the oil pressure. **** this website! If it stays below 175 alot, then I would do 25-40 hour oil changes just to be safe. Shell Rotella T 5W-40 Synthetic or any HDEO 15W-40 should do nicely in that drain interval.

 

[JimG]

No place on my dash for an extra gauge. I'm going to shoot the oil filter canister this weekend to see how hot the oil is getting.

 

[1 FMF]

if you're really gungho about this, pick up a mechanical oil temp gauge from local part store. Auotmeter I think. Not familiar with holman moody, but I have a '76 351w. Should be able to get a brass T fitting and measure temp where the oil sender is located, next to the oil filter?
You can also pick up a cyberdyne digital oil temp gauge from jegs/summit for $60. I have a couple and they are accurate to 1 deg.
For kicks when I get mine in the water sometime this summer, I plan on just laying the gauge in the cupholder outside the engine for a day to get a temp reading- no reason to mount the gauge permanently.

My best guess is the jabsco pump is pumping a large volume, not a bad thing, and your thermo housing has a bypass in it so the extra volume/pressure is circumventing the thermostat causing the low coolant temp. have you looked into the cooling system in detail? what exh manifolds do you have, and how many hoses going to it and the risers?

I wouldn't go to any extremes in labor or dollars until you get a good idea what typical oil temps are. If it's coming down to 25psi at idle, I'll bet the oil is getting fairly hot and you don't have a cold oil problem, which would necessitate frequent oil changes. I would stick with the multigrade 40/50 weight oils.

 

[JimG]

My manifolds are Edelbrock aluminum log-style, the risers are Holman Moody snails. (I know I give up TONS of horsepower with this exhaust, but they look SO good & original...) They are fed with a 3/4 inch hose from the t-stat housing. Water flow from my exhaust (through hull) is very good.

 

[JimG]

I shot my oil filter with my infrared this weekend.

The results: After a hard run in 87 degree water, the filter was showing 200 degrees. After a long idle back to the houseboat, it showed 155 degrees.

 

[Ryan00TJ]

With temps like those I would not lose one wink of sleep at night. The only thing I can see happening is that it might take your motor longer to warm up than most and some fuel dilution might result. Keep modest drain intervals and you should be good to go.