Overheat, Low Oil Pressure, and misfire?

[Jay Gadsby]

Hey Guys/Gals,

Recently I was out on the lake in my 86 Pachanga 22 (5.7/Alpha One). Was cruising along at about 4400 rpms, not max for the prop I am running, but moving none the less. All of the sudden I lost RPMs without moving the accelerator, the engine overheated and I lost oil pressure, within seconds I mean. I immediately decelerated and killed the engine. After a few seconds of WTFing, and not finding any sort of visible faults (checked the oil and such to no avail), I tried starting it up again. The temperature was normal, the oil pressure was a little low (10 at idle, maybe 30 at the most now). The real issue is with the firing. It seems to be not firing on two cylinders on the right bank (as viewed from the front). I need to test to ensure spark is getting there, I need to pull the plugs and ensure no foreign matters (like water) is in there. I am thinking headgaskets, but am confused on the low oil pressure part. Anyone have any ideas?? Thanks a lot!!!

SSG Jay Gadsby

 

[spdracr39]

Re: Overheat, Low Oil Pressure, and misfire?

Sudden overheat and low oil pressure sounds like a spun bearing but doesn't explain the dead cylinders.

 

[retrota79]

Re: Overheat, Low Oil Pressure, and misfire?

agreed with spun bearing, but does it knock at all? how long have you ran it after this happened?

 

[Jay Gadsby]

Re: Overheat, Low Oil Pressure, and misfire?

No knocking, and only long enough to get me back into shore. None at all since.

 

[retrota79]

Re: Overheat, Low Oil Pressure, and misfire?

i would get a mechanical guage on that thing, take the distributor out and prime that pump you will find out right away if that pump is pumping or not, i would not run it anymore how it is. if the pump is only pumping 10 psi? seems shot. but i would check to see it its the pump first. i guess you could compression check the cylinders too to see if it was all of a sudden gaskets that are causing the miss fire.

 

[Jay Gadsby]

Re: Overheat, Low Oil Pressure, and misfire?

the only thing I can think of is maybe water soaking the cylinders? enough to quench the spark but not hydrolock maybe? I will be pulling it home this weekend and troubleshooting. I am fully prepared to pull the engine for the winter anyhow.

 

[cr2k]

Re: Overheat, Low Oil Pressure, and misfire?

sudden overheating can be caused by a few things, catastrophic failure of the impeller, or maybe catching an ice bag on the leg covering the water intake.

May have fried a piston, head gasket or valve. Probably time to pull the heads.

BTW there is NO left or right on a boat it would be confusing as you described it. Standing at the stern of the boat looking toward the bow what you see on the left is the PORT side. the right side is the STARBOARD. This takes all guess as to where you are referencing L or R from.

 

[Jay Gadsby]

Re: Overheat, Low Oil Pressure, and misfire?

Considering the temperature on the short return trip was normal I am doubting an impeller issue. I did not see any debris, but at speed it is hard to tell whats below the surface.

I understand starboard, port, bow and stern thank you. But most engines are reffered to as left and right bank as viewed from the front. In a front engine rear wheel drive car, the left bank is on the right side. Same with a boat. Excuse my terminology, I will leave it at the door next time so no one gets confused.

 

[dubs283]

Re: Overheat, Low Oil Pressure, and misfire?

the alpha one and earlier mercruiser drives use a smaller, plastic housed water pump in the drive

overheat at higher rpm is a common occurence with these style pumps, you may not have an overheat issue at idle/lower rpms - i'm sure you took it easy on the throttle on your trip home

that said, yes, a head gasket issue is most definitely a possible cause of your spark/loss of power issue - a compression test is your FIRST troubleshoot, i would be suspect of #3 and #5 if i follow your explanation of cylinder banks

after that, an inspection of the water pump in the drive is in order

as far as oil pressure??i would get the other stuff resolved first, then start with a fresh oil/filter change and go from there

 

[NHGuy]

Re: Overheat, Low Oil Pressure, and misfire?

Hey Jay keep us posted on your findings. I run my 5.7 like that too. BTW the last time I ran her this season I was wide open throttle and got some funny sounds so I backed it down to 4000 rpms. When I got home I pulled the plugs to check and found one that had backed out of the head a bit, it was either #2 or #3.
Hey I want into the right/left fight. I say the port side of the engine is the left side. I work in the car biz, we always refer to sides as viewed from the driver position, not from the front unless you mean front seat.
IMO The left side of the motor is not on the right side of the vehicle.

 

[coheej]

Re: Overheat, Low Oil Pressure, and misfire?

Considering the temperature on the short return trip was normal I am doubting an impeller issue. I did not see any debris, but at speed it is hard to tell whats below the surface.

I understand starboard, port, bow and stern thank you. But most engines are reffered to as left and right bank as viewed from the front. In a front engine rear wheel drive car, the left bank is on the right side. Same with a boat. Excuse my terminology, I will leave it at the door next time so no one gets confused.

In the USA the left bank is on the drivers side of an automobile.

Do a leak down to see what you've got.

 

[Alpheus]

Re: Overheat, Low Oil Pressure, and misfire?

But most engines are reffered to as left and right bank as viewed from the front. In a front engine rear wheel drive car, the left bank is on the right side. Same with a boat. I will leave it at the door next time so no one gets confused.

I dont know where you are from but thats WRONG.

Sounds like you are the one thats confused.

Leave the tude at the door. No one likes to help out a smart @$$...

 

[Bondo]

Re: Overheat, Low Oil Pressure, and misfire?

Hey I want into the right/left fight. I say the port side of the engine is the left side. I work in the car biz, we always refer to sides as viewed from the driver position, not from the front unless you mean front seat.

Ayuh,... Agreed,... The portside is Always the portside, regardless where you're standing or sitting...

 

[Silvertip]

Re: Overheat, Low Oil Pressure, and misfire?

Low oil pressure is rarely the sign of oil pump failure. Yes -- it does happen but rarely. Low oil pressure is generally an indication of a mechanical failure in the rotating assembly (rod or main bearings). After an overheat, or indication of low oil pressure, then running back to shore is like Tim Allen on Tool Time telling the story about how his wife blew up the Buick. When asked what happened, his wife says "it just quit!" Tim says, didn't the OIL LIGHT come on? She said Yes! Tim says "and what did that mean to you?" She says "if it was important it would have come on brighter!" My gosh folks -- when an oil pressure or temp gauge says you have a problem, it means you have a problem NOW, not next week, not after you get to shore, or perhaps tomorrow. Paddle, push, or tow the rig to shore to limit additional damage. Boats have instruments for a purpose -- watch them like a hawk.

 

[Jay Gadsby]

Re: Overheat, Low Oil Pressure, and misfire?

All the technical manuals for all the AM General 6.2 and 6.5L diesels in our HMMWVs, Detroit 8V92TAs in our HEMMTs, and all of the diesels powering all of our armored fighting vehicles, all read to state the orientation of the engine is viewed from the front. Same with my VG30DETT manual for my Nissan 300ZX, and my VK56DE found in my Titan... I am from America thank, there is no attitude. Most people that do not tear apart diesel engines or otherwise do not normally read the technical manual and therefor do not know that they are labelled backwards for that particular orientation of engine. That is why I made it a point to specify. I came on here asking a simple question since I am not the end all for marine engines. I am still learning them as I know there are certain nuances that are different from your normal automotive engine.

As for the gentleman above, I do watch them like a hawk, hence the fast shut down, and with reluctancy I started the boat back up after letting it sit to cool down. I was 5+ miles from the ramp, and there was literally no one out at the time. Needless to say the engine is coming out for a rebuild soon anyhow. It survived 24 years of abuse by the previous owners and myself, but nothing is infallible, not even the great 350.

SSG Jason Gadsby
1-7 Cav. 1st Cav Div.
Fort Hood Texas
(In case you wondering what country I fight for)