tomkat60

just purchased a used boat with twin 454's one engine's oil pressure drops 20 lbs lower than the other engine when in neutral @ 2800 rpm's, installed temp gage at same location as temp senders for alarm and pressure gages, the temperature never gets above 100 deg's even after eng temp get to 140 deg, raw water cooled, the oil filter gets hot about 110 deg, any help would be appreicated

Thanks Tom

MILD THUNDER

iTrader: (3)

Are you sure the gauges are good and the senders match the type of gauge(brand).. If i remember right some gauges, like gaffrig, required the use of a gaffrig sender.

Are you saying you put the temp sender in the oil filter housing and thats where you saw 110 deg?

tomkat60

the temp probe is installed in the same location as the alarm and pressure gage senders, I took the filter temp with a temp gun, both engines have the same senders and gages
thanks

fireboatpilot

Don't quote me on this because I'm not sure but shouldn't the oil temp sender be installed in the pan? I doubt that the sender can tell the difference between oil temp and block or metal temp being that close to it? Am I wrong?

MILD THUNDER

iTrader: (3)

You can take readings at the filter housing, but temps are usually higher there than what the sender would read if it were in the pan.

Griff

Why are you reving engines to 2800rpms in neutral to start with??????? Free reving is very hard on the engines.

Oil temp should be taken from the pan. The location you have it does not work, nor will the filter location. If you only had 100* oil temp, you would have all kinds of moisture in the oil and it would be milky. Get a point and shoot infrared temp gun and point it at the oil pan.

Young Performance

I don't like to measure oil temp in the pan because it takes the oil cooler out of the equation. For example, lets say the oil in the pan is at 250*. If you have a small oil cooler, then the engine may be seeing oil that is 230*. Now if you have a larger cooler, the engine may be getting oil that is only 190*. You want to know what the engine is seeing for oil temps.

The biggest key is to be sure that you have the oil temp sender in the flow of oil. If it is put in a dead end oil passage, it willnot give a correct reading. In a Gen VI block, the best place is just above the stock oil filter pad. That will put it in the flow of oil just as it enters the engine.
I would install some temp. oil pressure gauges to be sure the pressure readings are correct and then go from there.
Eddie

tomkat60

thanks for the replies but I still have questions about the temp, this is a 32 ft fishing boat, max speed about 35mph, oil temperature is 115 degs. reading with a temperature gun on the bottom of the oil pan, do I need to bypass the oil cooler to get the temperature up and if so what should the temp. be

these engines are stock, remains with less than 300 hrs, the oil pressure sensor is located above the oil filter adapter area, there are no ports in the distributor or pan area for connections
Thanks for the help
Tom

getrdunn

iTrader: (7)

I would bypass the coolers. That can be done easily and see what you get for temps. I realize the importance of external coolers however in many marine applications especially with stock engines they can be overkill. A lot of the older boats Merc didn't even have coolers. I have 13 plate coolers in my TRS 496's however they are thermo controlled as well as overkill. Running to low of oil temps are hard on an engine. Also free reving is OK to a degree. 2,000 o 2,500 rpm is where your engine runs with the least amount of strain.

Griff

I really cannot understand how you can really have 115* oil temps. That is so extremely low, thats its almost unheard of. How cold is the water in the lake??????