Odd issues with 1984 CVX-16 - looking for advice...

[baylk]

Hi everyone!

I would like to pick your collective brain about some issues with a 1984 CVX-16 with a Johnson 120 that I got from one of the members on this board. I’ve had it a few months and its been running flawlessly until (of course) July 4th on Minnetonka. The story is a bit long, so you may want to grab a beverage of choice as you read this. ☺

My wife and I figured we would take a quick spin around the lake and get off before all the crazies got out. The boat ran like a champ for 1-2 hours at all RPMS and seemed fine. Right before a channel I bumped up the speed to around 25-30 to pass a large boat that was creeping along. At that point the engine shut down and the alarm went off with a constant tone. From my understanding that’s overheating or fuel starvation and the VRO signaling an issue (I’ve heard of this VRO alarm but can find no concrete documentation it actually exists.)

Anyway it refused to start and made no noise like the starter was even engaging so we got a 50’ tow to a dock to troubleshoot.

Lights worked fine, as did tilt, but motor was dead. I figured the battery was low so we hitched a ride and went home to get a spare battery for a jump. After jumping (and an about 30 minute “rest” for the boat), the starter spun but would not engage. I fiddled with the bendix and that seemed to make it happy. It started and ran the next 40 minutes at low-ish rpm (20 mph or less) with no issues.

In looking over the engine after that I had some thoughts:

The clamp on the fuel line where it exits the hull leading to the motor had broken and come off. Air leak, and the VRO alarm that may or may not exist?

Overheating even though the water flow seemed ok? This boat has a pressure gauge on the water, but I have no idea what a normal reading is. Interestingly higher pressures DO NOT correlate with higher RPM. For example: (I assume the gauge is in PSI?)

Idle – 4 PSI
1500 RPM 8 psi
2700 RPM, 15 PSI
3500 RPM 6 PSI

Do I have something going on with the water pump?

And, lastly in really digging around checking everything over, the battery does not appear to be charging. With the motor off I got a reading of 12.1v, once started it slowly dropped to 11.9, 11.8, 11.7, etc. The tach works fine, so I assume the stator is ok, and maybe it’s the voltage regulator. I’m going to look into that more now that its out of the lake.

So, long story to ask any thoughts about the alarm and engine shutdown, or any of the above? Would a low battery kill a running engine? I did not think so, but I’m better at wrenching on I/Os and car.

Thanks everyone!
Scott

[Rich_V174SS]

First off, a constant alarm would most likely indicate an overheat. Check to make sure you can turn the flywheel by hand and that the engine isn't seized up. Check the spark plugs for any metal bombardment that could indicate a shredded piston.

An air leak may cause a lean condition, less fuel into the carbs. You can possibly score a piston from lack of fuel. If the engine isn't seized see if you can do a compression test of the cylinders. Not sure if your engine has a fuel line vacuum switch that would trigger an alarm if there was too much vacuum draw on the hose from a blockage. But the VRO would probably signal an alarm if there was no oil going through it.

If the battery isn't charging the engine wouldn't be using up the power when running. But the gauges and anything else in the boat turned on will. The motor generates it's own power to run through the stator and ignition system.

[baylk]

thanks for the reply - the engine is fine and working well, not seized up and performing fine today. Oil flow is fine as well, as far as I can tell. I ran it about 30 minutes from our place to the launch to pull it out and it ran perfectly after I charged the battery to be safe and clamped the fuel line.

In the case of an overheat, will the alarm shut the engine down completely? It pretty much was like a light switch - running great and then off just as if I pulled the kill switch...

thanks!
S.

[Rich_V174SS]

I'm pretty sure there's nothing on that engine to shut the engine down aside from your key switch or emergency lanyard. They didn't have such a safety feature as far as I know. It would sound to me more like a bad connection someplace. I've seen key switches go bad where the engine runs for a while then breaks up and dies. The problem is internal arching of the magneto kill wire inside the switch shutting down the ignition system. Could be affected by humidity. Replacing the key switch usually fixes that. I have also seen ignition power pack failure do the same thing. Another thing to look at is either of the big red connectors on the harness for possible corrosion or internal shorts or continuity problems. They're notorious for causing mysterious electrical problems. Or frayed wiring inside the control box and key switch, if something is touching the control box casing you'll have a short to ground. If it's the black/yellow magneto wire that will kill the engine. Old wiring can be fun to troubleshoot.

[Rich_V174SS]

Another thought - If your engine overheated check that wires didn't melt to the engine block. Same thing could happen. If a temp sensor wire melted and made contact with the block it could set off the alarm. Same for the black/yellow magneto wire, it could cause the engine to shut down. I've seen lots of crumbling insulation on wire harnesses draped around the top of those engines. They need to be checked thoroughly.

[GCarlover]

I will try and help with  my experience on a 1987 140 Johnson.  I have a pressure gauge and as I remember it runs over 20 lbs and drops at high RPM s because of a bypass valve.  The newer 88 and up have a S.L.O.W. protection that cuts rpm when overheated.  Pretty sure you need a water pump impeller replacement.  The rectifier may be bad.  Should charge 13 to 15 volts.  I've replaced it  and also the power pack early on. (Tach may not work with it out)   The oil tank warning I believe is 20 sec buzz.  Mine also went intermittent.  Disconnected the brown wire and now watch the oil level.  All or any members please verify this.

[David CVX-16]

http://www.maxrules.com/vrowarnings.html

[Plugcheck]

My 01 merc 90 had vro, the warning horn would operate intermitantly when the low level was approaching.  Mostly happened in rough water when bouncing around.  My 79 merc 115 does not have vro, when the horn turns on it's one of the two heat sensors has reached set point, horn is constant until it cools down. 

[GCarlover]

One added note when my impeller went bad (over the winter) it wouldn't pump any water with the muffs.  When you run in the water the pressure on the intake is higher.  With my 20 hp the horn would sound at idle but go off as I increased speed.

[baylk]

Thanks everyone for the input. In checking the regulator is indeed bad, so that being replaced. I'm also going to do the impeller since my pressure is WAY lower than 20. I suspect its bad, or something is plugging the pump. I figured since its out of the water I might as well address that at the same time!

David - thanks for the VRO warning list. Interestingly mine does not chirp on start, but it obviously works just fine in some cases. I find the same to be true on my other 1984 CVX-16 as well....

S.

[Hyperacme]

Good read about VRO system.
http://continuouswave.com/whaler/reference/VRO.html

My 115 HP Mariner (4 cylinder) get about 5 psi at idle, to about 28 - 30 psi at WOT.
New impeller last year.
If unsure how old yours is ... Change it !

[baylk]

Greg - thanks for the link to the VRO info! That upgrade with the LED indicators may be a good winter project!

S.