Low oil, risers are hot

[mark_fitzy]

Well I finally got to take my 1995 18ft Regal bowrider sterndrive with its new rebuilt Chev 262 1995 4.3lt V6 motor installedfor a spin in the river.

Everything went well, Oil pressure was 80 and temp was cool at the start and after about 20 mins I noticed the oil pressure slowly dropping. I put this down to motor getting to temp. The longer I went the oil pressure kept dropping, down to 60 and then down to 40 and then down to 30. The temp gauge did not change, Until I took it down to idle and then the temp went up to 170 and oil pressure to 0. I quickly increased acceleration and then oil went back up to 30 and temp went down, I drove a bit longer and the oil went down to 25 so I slowed down and oil pressure went down and temp didnt raise much higher then 170 but a constant alarm was going off, so I turned engine off. I waited a minute and engine would turn over but didnt start so I waited for a minute and then started the engine, the alarm was on until I gave a bit of acceleration and the alarm went off.

I went back to land(swimming distance) and checked the motor and the risers where hot to touch, I tried to checked the oil dipstick and it was also super hot.

I waited till the engine cooled down and checked the oil, it was inbetween 1/2 and 3/4 full?

Any ideas?

Also, does it matter what side of the thermostat the temp sender and the alarm switchshould be? because I know the mechanic was having problems with the alarm going off so he switched the positions, he put the temp sensor on the port side of thermostat and the alarm on the starboard side of thermostat

 

[funk6294]

Re: Low oil, risers are hot

Sounds to me like the alarm is working, the gauge is broken, and your mechanic still has not figured out why the boat was overheating in the first place. By the way, I read your other thread about having this motor put it, was this the same mechanic that did the motor intall prior to this motor???

 

[mark_fitzy]

Re: Low oil, risers are hot

Yes it was the same mechanic, and yes I know I was an idiot to get him to install, but I didnt know any other mechanics that I knew that had a good reputation, (better the devil you know theory).

 

[JustJason]

Re: Low oil, risers are hot

run the boat with a mechanical gauge..... better yet... bring the boat back to the mechanic and tell him to run it with a mechanical gauge.

 

[ziggy]

Re: Low oil, risers are hot

that don't sound good to me.

i/m not the pro by any means so i have to refer to the service manual. i usually go to the trouble shooting guide.

your oil pressure don't sound like it's acting proper to me. for mine, the spec is 2k rpm and pressure should be between 30-60 psi. mine runs in the 40 range and i don't think it drops much below 20 at idle, from memory. on mine lowest oil pressure is at idle, the faster the engine runs, the higher the pressure goes up to 40. it's always constant at that point.

i think i'd get a manual oil pressure gauge and find out an alternative reading to what your gauge is saying first and before assuming the worst, but sure seems like it needs looking into.

fwiw, my temp don't change much either after warmup. and it don't change much from idle to wot either. i don't have numbers so can't refer as to what the actual number is.

look at your s/m trouble shooting guide and see what it says about low and high oil pressure. for my rig, it refers to things such as.

for high reading- inaccurate oil pressure gauge or sender, clogged or restricted oil passage, oil pump relief valve stuck closed.

for low reading- oil level low, thin or diluted oil, inaccurate oil pressure gauge or sender, oil pump relief valve stuck open, oil pump pickup tube restricted, worn parts in oil pump, air leak into pickup side of oiling system at oil pump gasket, around pickup tube (where installed into pump) or hole in pickup tube, excessive bearing clearance, oil leak (leak can be external or internal) 1 oil passage plugs, 2 cracked or porous cylinder block. these are things to check for my rig. consult your service manual for items that are more pertinent to your engine. look at the items for over heat conditions too. the book should give my many ideas as to the failure.

0 psi oil pressure would worry me.

 

[Don S]

Re: Low oil, risers are hot

Assuming for a moment that the oil pressure sender/gauge are correct, and I have had this happen before. If the crankshaft was trued or polished .002 or .003 below size and there was too much gap for the standard bearings, the engine would not knock or anything, but the oil pressure would drop down to 0 or nearly 0 when the engine and the oil warmed up and at idle.
The temp sender and alarm should work on either side, but the wiring going to the proper sender/switch would be on the wrong one if they were installed on the wrong side.

 

[JustJason]

Re: Low oil, risers are hot

If the crankshaft was trued or polished .002 or .003 below size and there was too much gap for the standard bearings, the engine would not knock or anything, but the oil pressure would drop down to 0 or nearly 0 when the engine and the oil warmed up and at idle.

Yep... when the oil is cold and thick the pressure is good, when the oil is warm and thin the pressure drops as it's spraying out of the mains when running. However if the bottom end was plastigauged during the rebuild (as it should have been) this would have been caught and wouldn't be an issue.

 

[Don S]

Re: Low oil, risers are hot

if the bottom end was plastigauged during the rebuild (as it should have been) this would have been caught and wouldn't be an issue.

IF is the word here. Most engine rebuilders do not go through all that. They bore em turn the crank and bolt it together. No time for all that plastigage stuff. That takes time and time makes the engines cost more.
Like I said, I have run into this before on rebuilt engines.

 

[mark_fitzy]

Re: Low oil, risers are hot

run the boat with a mechanical gauge..... better yet... bring the boat back to the mechanic and tell him to run it with a mechanical gauge.

I have already done that twice, as the first time they couldnt get a reading at all and so they put a manual gauge on(so they say) and it read correctly. I am not sure what they did but then when I went to pick the boat up,they said the oil pressure is reading great now.
So I took the boat for a run and in 5mins alarms went off so I took it back. They had it for a week and said everythng ok now ,they said all good to go, oil pressure is fine we took it for a water test and everything is fine. So I cant see the point to take it back to this joker again. I think I will find a new mechanic and get himto check it allover. I dont understand if he had taken it for a water test(as he said he did) why he wouldnt find what I found after 20mins

 

[mark_fitzy]

Re: Low oil, risers are hot

Assuming for a moment that the oil pressure sender/gauge are correct, and I have had this happen before. If the crankshaft was trued or polished .002 or .003 below size and there was too much gap for the standard bearings, the engine would not knock or anything, but the oil pressure would drop down to 0 or nearly 0 when the engine and the oil warmed up and at idle.
The temp sender and alarm should work on either side, but the wiring going to the proper sender/switch would be on the wrong one if they were installed on the wrong side.

Thanks Don, I will check the wiring this afternoon. How can I find out If the crankshaft was trued or polished .002 or .003 below size and there was too much gap for the standard bearings, the engine would not knock or anything, but the oil pressure would drop down to 0 or nearly 0 when the engine and the oil warmed up and at idle. is the problem?

 

[mariner1900]

Re: Low oil, risers are hot

By Mark : How can I find out If the crankshaft was trued or polished .002 or .003 below size and there was too much gap for the standard bearings, the engine would not knock or anything, but the oil pressure would drop down to 0 or nearly 0 when the engine and the oil warmed up and at idle. is the problem?

Easy! Pull the engine. Take the crank shaft out and use a micrometer and measure the crank journal sizes or plasti-gauge the bearings.

But doing that would void your warranty. Best you start to contact the the engine supplier if the oil pressure is indeed "LOW".

 

[mariner1900]

Re: Low oil, risers are hot

Hi Mark, As well what grade oil did the mech put in the engine. If wrong grade (too light) when the oil gets hot it thins out too much. This can also cause low oil pressure most notably at idle.