What to do?

[64 inboard]

Been a while since Ive posted. Ive got a 64 Correct Craft boat with a 170 six. The oil pressure has been doing some funky things. On cold start it reads 35-40 lbs. After warm up, while cruising around 2-2200 R's, it s dropped to around 5lbs. (and yes, it has oil) It will occasionaly, for what appears to be no reason, go back up to the 35-40 range, only to have it drop back down again. Not sure, but my thoughts are , worn oil pump or dirty/plugged pickup screen?

Earlier this spring I ran a comppression test (not related to this, just doing a tune-up) . The manual shows it should have 160 lbs.(really?) Im running 130 even, within a lb or two, across the board. I know this isnt related to oil problem, but wondered if the 130's normal?

 

[early ford fan]

worn out bearings imo.i had a 460 mustang that would do that.

 

[mach1 mark]

Its the gauge not the engine. I don't know about old boats, but in the mustang it has a voltage regulator on the back of the instrument panel., The oil gauge doesn't become erratic it just gives odd readings. Check the other gauges and see if those are also odd.

 

[64 inboard]

I re-wired the boat a couple of years ago. I replaced all the gauges at that time. The original gauge had an electric sender. I replaced that with a mechanical SW gauge. Im thinking about installing another gauge on the motor so I can monitor it there also. I also thought about bearings, but why would the pressure fluxuate, wouldnt it just stay low, especially after warm up?

 

[sixpony]

I had the same problem with my jeep 4 banger, had a lot of carbon in the oil pan, when you shut down it would fall away from the screen and then get picked up again when it got agitated, if your sure the gauge is accurate then that would be my next step, probably a pain to get the pan off in a boat but if that's not the problem, your probably in for an overhaul anyway.

 

[rbohm]

8) assuming the gauge is correct, i would first check the pressure relief valve in the oil pump for proper operation. sometimes they get stuck in a slightly open position and the oil pressure drops. also check the pick up screen for debris. then check the pick up and the oil pump and make sure the connections are tight and not drawing air.

if these check out, then look at the tubing that feeds the gauge, if it is clear you should be able to tell if there are any air bubbles in the tubing that will give a false reading.

 

[mach1 mark]

I meant the Voltage regulator is bad, not necessarily the gage

 

[rbohm]

I meant the Voltage regulator is bad, not necessarily the gage

8) he is using a mechanical gauge.

 

[early ford fan]

you could ad some stp oil treatment or run straight 30 weight oil.

 

[64 inboard]

sixpony is right it is a pain to get the pan off. You need to pull the engine / trans to remove it. Its a flywheel forward setup. It isnt tooo bad to pull the combo, but can be a PITA to re-align the prop shaft when installing again.The motor is mounted backwards,where the gearbox drives from what would normally be the front of the engine. The trans actually is open to the oilpan, and shares engine oil. Here are a couple of pics of the engine...

I do plan on a rebuild someday, but was hoping to get thru another year or so, timing isnt the best right now.



:

 

[JackFish]

Just curious, how do you change the oil?

If sludge or deposit build up are a concern you might consider this product:
http://www.auto-rx.com

 

[64 inboard]

You have to pump the oil out , thru the dipstick tube... not a fun or fast job. I dont think that sludge from carbon is a big problem. The boat motors usually run pretty clean, they dont get many hours per year, plus they never see any dusty conditions.

When I took the valve cover off to adjust the lifters, the head is very clean. Im wondering since the gearbox shares engine oil, if the fiber from trans clutch plates could be the culprit blocking the pickup screen?

 

[64 inboard]

BTW, I do have what is supposed to be a 200 from a Maverick (how can i tell for sure?) that Im thinking about using when the repower day comes, Im told this is a direct replacement? Are the oil pan, front and rear block bolt patterns the same? / how much HP can you get from a "mild" overhaul? Sorry for the dumb questions..

 

[early ford fan]

if it has five freeze plugs below the intake manifold and a three bolt water pump its a 200.if the starter is in the same place as your 170 it is a direct replacement.you can use the numbers on the block to know what year the engine is....c6 means 1966 d5 means 1975....

 

[64 inboard]

Im pretty sure it has five freeze plugs on one side of the block. I'll have to dig it out to get the casting numbers, where would they be located? As for the the three bolt water pump, what would the 170 normally have? As you can see in the picture, the motor itself doesnt have a water pump mounted to the block. It uses a raw water pump(below alternator) driven by a belt to cool the engine. Im not sure if the original water pump holes are used on this engine?

As I see it, the main things I need to be concerned about, are that the oil pan, front motor mount plate(where the "car" bellhousing would normally be), rear motor mount/trans adapter plate and any other accessories that bolt on, would have the same bolt patterns as the existing 170.

The 170 is rated at a 100hp, what can be expected from a "lightly" worked over 200? to start its almost 20% larger in cubes.

 

[69.5Mav]

When you get low oil pressure do the lifter make noise, only if they are hydrolic, solids won't?

First Lets start with the easy things.

Change the oil.

Next if this does not cure it install another oil presure gage.

Still got a problem then.
Prepare the 200 for instalation and swap them. The 170 was rated at 105 HP and the 200 was rated at 120 HP, these rating are suspect but should establish a stock ratio between them, so a 14% gain in HP all things being equal.
1) Take the pan off and examin it for debree. Examin the pickup for blockage. and examin the oil pump for anything that looks out of ordinary.
2) Plasigage a few rod bearings and maybe one main bearing, does it have four or seven main bearings. If rod bearing are too lose replace with new ones if the crank looks good.
3) replace the oil pump with a new one.
4) Asumming you had to remove the engine to do this, put the engine on an engine stand and start it to check the oil pressure.

Hopefully you'll find your problem.

Good Luck

 

[Lazy JW]

.......

When I took the valve cover off to adjust the lifters, the head is very clean......

Probably not a sludge problem; I've seen sludge but it does tend to get all over the engine

Im wondering since the gearbox shares engine oil, if the fiber from trans clutch plates could be the culprit blocking the pickup screen?

Dunno about clutch fibers but I think something is either blocking the inlet (doubtful) or the pressure relief valve is sticking.

If you can access the oil filter passageway, try removing the filter and using compressed air to blow backwards through the pump. I don't believe it can hurt anything and it may dislodge any debris.
Joe