scarab39

My gen 6 540's have the Canton 8 inch deep, 9 quart pans on them. I put 9 quarts of oil in it, plus enough to fill the cooler, filter, and lines. When I get over about 4500 rpm, the oil pressure starts to fluctuate. The motor just got new bearings and oil pump, but it still fluctuates. The pickup is exactly 1/4 inch up from the pan bottom (it was about 3/4 inch). I switched the gauges (mechanical) also. The oil pressure is good at idle (60) and stays between 55-70 at all times until about 4500 where it will start suddenly fluctuating between 30 - 60. I installed a large cooler, an-12 lines, and kn6002 filter. I don't know if I need to try adding oil or removing some. Does anyone run this pan/ have any advice on what to try next?

stevesxm

if you are really getting that kind of fluctuation you have one of a couple things going on...

first starvation... which , on the face of seems really unlikely UNLESS the bootom of the pan got pushed up against the pickup when you were installing it... and this is a real possibility...

second... the relief valve is popping off and hanging... this will sometimes happen w/ hi volume oil pumps at high rpm... not common but i have seen it... but the bottom line is you have to find this... the oil press gage is like the fuel press gage... in what it tells you... if the numbers suddenly drop then there is essentially no oil ( press in critical parts of the system) at that moment... as the clearences try to " refill" ...

there may be other causes but on the face of it, thats where ide look.

if it worked ok BEFORE you worked on it, you need to go back and look at what you did... like simple stuff... like you got the lines on correctly etc...

scarab39

I plugged the bypass valve in the block. This is a new boat for me and I'm still trying to work out the problems. On the dyno this motor didn't show any problems. I'm thinking it's either starvation or aeration of oil but I am new to this kind of boating and I'm not familiar with this kind of problem so any advice is much appreciated.

thanks!
chris

stevesxm

well... i can't see starvation w/ a 9 qt pan unlees you are doing 3 g turns... but if the pickup is crushed against the bottom of the pan then that will do exactly that... and 1/4 inch isn't nearly enough in my opinion...

areated oil would have to come from the crank beating the oil into foam... and if it didn't do that before, why would it do it now ? not to mention it would drive the oil temp VERY hi...

you never answered... is this a new problem....i.e... did the old motor do it ?

scarab39

I bought this boat with the motor bad so I have never seen it run right. the second motor holds 40 psi constantly. I went with a hv oil pump when we put this motor together. It ran fine on the dyno up to 6k with the same cooler, lines, etc. I put it in the boat and the pressure fluctuated the first time out. I pulled the motor, put in a new pump, set the pickup lower (it was at about 3/4 inch), and blocked the bypass. Same thing is happening. Could it me the pressure relief on the pump? both pumps are melling hv

btw, the oil temp never got over 180

mopower

Have you tried a mechanical gauge yet? Not quite sure about the "8 inch" Canton pans. I have 10 quart Cantons on my Merlin 540s and never a problem.

stevesxm

geeze... wouldn't think so... but should ONLY have one reiief valve in the sytem... i might be sorely tempted to take all the coolers etc out of the system just as a test... just plug them and loop the filter lines... so that the oil system is just the motor and the filter..... and do a test flight... also... there have been 50 threads here with people describing alien voodoo things happening w/ oil filters failing... you might just throw a filter at it because its cheap... ALSO

do i understand you correctly when you say that the other motor is plumbed exactly the same yet runs steady state 40 instead of all these high and wierd number this motor does ? how do you explain that ? if true, doesn't that samck of some more fundemental problem

scarab39

both gauges are mechanical.
Yes, both motors are plumbed EXACTLY the same.
I've read several of the threads on this site which drove me to buying all new cooler (from CP), 12-an lines, filter mounts, accumulator, etc. I blocked the bypass under the filter mount and left the pump bypass alone.

My (uneducated) guess is that the existing motor has a stock pump and is pumping less oil into the motor (only reads 40 psi). I've replaced the filter with the same type, and switched to straight 40 weight oil (from 20w-50).

mopower: do you run exactly 10 quarts (plus filter/etc)?

mopower

Dry at first fill up was close to 12 quarts with empty filter , cooler and lines. Now a change is about 10 to 10 1/2 quarts.
Here's the best (and only ) shots of my pans. Not sure if it will help , but here they are

SB

You might be aerating the oil with the larger stroke crankshaft. Reduce oil level by 1 quart at a time (no more than 3) and see if pressure holds steady.

Canton calls out exactly what pan holds. Does not account for anything else.

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You mentioned new bearings and oil pump. Why ?

What kind of crankshaft (man + model) ?