Engine cuts out randomly over ~20mph - RESOLVED!!!

Dude_Himself

The other thing not mentioned is the ignition switch (key). As they start to fail they can randomly cut out like this due to corrosion on the contacts. At first exercising them (key to START then back to ON or jiggling) is enough to cause it. Although I would expect the same behavior at lower speeds, but perhaps there isn't enough vibration consistently?

binduni

UPDATE: well, sort of. After many discussions and lots of raised eyebrows when mentioning the gimbal bearing as the culprit, I found a small shop nearby that laid out a plan of attack - first time I've come across this! So, bringing my baby to him next weekend. I'll update again in a few weeks.

Stodge

Alswagg said:

You have an Alpha drive.  Check the shift interupter switch, shift cable adjustment.   Don’t over think things.  It’s just a boat, nothing special very basic engine 

I had one of those come lose on my 280.  It shook enough to engage the cut-off.  Worth looking at.

Willhound

If its not the gimbal, one thing that hasn't  been mentioned is to check for a wire, usually orange or yellow that runs from the positive lug on the starter to the coil. It acts as a full clean power feed to boost the coil. I had issues on my 270 similar to what you describe. I'm a 5.7 but wouldn't be surprised if the 5.0 is the same.
Mine started out as an intermittent cut out, almost like someone quickly shut the key off and then right back on. That wire was loose and only seemed to have an effect when on plane and engine revving a little higher.

binduni

UPDATE: New shop, and these guys have done a thorough investigation (seemingly). After running diagnostics, both in a tank and on open water, they found the fuel pressure to fluctuate dramatically when over 2k RPM, and have reproduced the cut-out many times. Each time the fuel pressure dropped, spiked, then dropped to nearly zero (remember, this is an MPI 5.0). They are now replacing the cool fuel pump. Let's hope this is FINALLY the solution! The way I look at it is; the fuel pump is flaking out anyway (it is 17 years old) so replacing it makes sense. I've been left stranded in many car with a bad fuel pump..... 

PickleRick

See...you should have gone with my first guess!!! 

I have no idea why the engineers don't install a sensor to read when fuel pressure is low and throw a low fuel pressure cel.  

Glassguy54

That cool fuel module  has been a really troublesome item. They painted the inside so that if any fuel containing ethanol gets in the system, it eats the paint and then gets into your injectors, causing all manner of problems. Stupid engineering! Also a big "Give me fuel without Ethanol in it, you lousy farm state ba$t@rd  Politicians" that mandate ethanol  blended fuels must be forced upon Americans.

PickleRick

Don't bad mouth ethanol fuel. That crap will pay my kids way thru college

Dream_Inn

PickleRick said:

Don't bad mouth ethanol fuel. That crap will pay my kids way thru college

You are definitely correct there.  It is the worst thing for small engines, period.  I always run startron in my small engines and then run the fuel out of the carburetor after each use. But, it's still bad for gaskets and O-rings.

PickleRick

I actually find less issues if properly treated and stabilized fuel is kept full in fuel tanks. Starting every few months to keep fuel circulating is also key.  Allowing fuel tank or carb grommets, o rings, fuel hoses etc to dry out then expand again once you refuel can cause them to contract/expand then harden/break/crack and leak.  4 strokes you can run out of fuel with less issue of rubber part damage but even humidity in the air can cause rust or corrosion issues when fuel isn't in there to displace the air.


Many boat and motorcycle manufacturers tell you to do this.  If it's good enough for a brand new hydrosport with 3 motors across the transom it should be good for my 500 dollar inverter geneator!

Black_Diamond

Ethanol is just an overall disaster let alone the reduction in mpg/power.  It has about 1/2 the thermal energy as gasoline. If you have an E-85 vehicle: go fill up with E-85 and watch your mpg hit near single digits. 

Ethanol mandates are just farm welfare. 

PickleRick

When my customers complain that my shop didn't do a good job on a repair because a carb was rebuilt a year ago and now doing the same thing i have 2 responses.

A. Why didn't you follow our fuel treatment and storage recommendations?

B. Vote


Not much else i can do for them.

GMSLITHO

Most important is “B”

Michael T

@Black_Diamond.....IMO 100% on the money and forget the environmental "benefits" of ethanol - the corn (and other cellulose-based ingredients) strips the soil of nutrients requiring massive amounts of fertilizer and also water. it's a crock!

binduni

So, ready for this? NOT the fuel pump. Yes, the pressure was irregular and throwing codes, but the cut-out issue still exists. 

Picked the boat up Saturday, got out on the water and within 15 minutes - BAM. Cut out.
Called the shop and he came right out with his scanner and jumped in the boat with us. We could reproduce the issue at-will, as always. Great guy and is committed to solving this issue. Next stop, gimbal bearing! :-)

reneechris14

I would put my money on the cut of switch where throttle is. Jump power to the plug on the motor. also check connections on the 50amp breaker on top but the plug and the 90amp fuse on the starter one must be loose. 

rasbury

When we first got our boat it would cut out- it was a bad starter which I had rebuilt and no problems since...bad ground?

dalek

I would not discount PickleRick's bee in the tank theory. You could try sucking out a few gallons of fuel through the tank pick-up tube using a Pela type extractor. You will need to fit something on the pipe with a 3/8"NPT male thread. Just to see if there is anything obvious in it. I have seen clean fuel filters in the engine but badly clogged pick up tubes and check valves. If debris in the fuel is quite large it won't make it to the filter.

PickleRick

You could also use a little 6 gallon outboard fuel tank temporarily on the deck.  The gimball should be checked yearly.  Wouldn't be a bad idea to pull the outdrive, check the gimball, replace bellows for good measure and cable/water tube if questionable. It would only take a few hours. Check the alignment while in there.

If solo on removing an alpha drive, drop the foot before removing outdrive.  Do your impeller while it's off.  The upper half is pretty light and can easily come off and back on solo without much fuss so long as alignment is proper.  Re attach foot after reinstallation of top half.  After doing this a few times I've come to the conclusion that if the outdrive slides on and off by myself with ease then the alignment is good.  Checking with the bar makes me sleep a little better at night

binduni

Hope you all are not bored yet with this saga..... but here's the latest.
The shop spent time in the fuel system at the tank and found the anti-siphon valve stuck partially open with a piece of plastic crap. They are waiting for decent weather to test on the water. Here's hoping they found the smoking gun!!!!

Dream_Inn

That looks like great news!  Please post results!

rasbury

I had this issue when I first got our boat- I was also having issues I thought with batteries when the starter eventually failed. I was loosing electrical contact through the starter that was shouting down the motor and would only happen at min. wake type speed...had the starter rebuilt for 125 and never had a problem since. Guy said it had gotten wet. Sits very low.. .my recent bielge fill issue has me worried about it again...I would think a weak ground could also cause this issue?

69fastback

Black_Diamond said:

Ethanol is just an overall disaster let alone the reduction in mpg/power.  It has about 1/2 the thermal energy as gasoline. If you have an E-85 vehicle: go fill up with E-85 and watch your mpg hit near single digits. 

Ethanol mandates are just farm welfare. 

If tuned properly for e85, it’ll make considerably more power than standard pump gas, more so in a power adder application. This is of course at the cost of significantly added fuel burn. I’m getting ready to build a turbo e85 car right now and it should easily make 1200 hp. And I mean easily. Stock heads, and cams. Just add turbo and e85. 

212rowboat

69fastback said:

If tuned properly for e85, it’ll make considerably more power than standard pump gas, more so in a power adder application. This is of course at the cost of significantly added fuel burn. I’m getting ready to build a turbo e85 car right now and it should easily make 1200 hp. And I mean easily. Stock heads, and cams. Just add turbo and e85. 

how big a freakin' turbo are you talking and what kind of displacement is the engine? what kind of boost?  surely you've studded and wired those heads down.... that is absolutely nuts! 

69fastback

212rowboat said:

69fastback said:

If tuned properly for e85, it’ll make considerably more power than standard pump gas, more so in a power adder application. This is of course at the cost of significantly added fuel burn. I’m getting ready to build a turbo e85 car right now and it should easily make 1200 hp. And I mean easily. Stock heads, and cams. Just add turbo and e85. 

how big a freakin' turbo are you talking and what kind of displacement is the engine? what kind of boost?  surely you've studded and wired those heads down.... that is absolutely nuts! 

88mm on 302 CID

Crower rods, stock crank, billet oil pump gears and some oiling mods. The coyote motors are amazing beasts. 

rasbury

Any up date on this issue?

binduni

Picking her up this Saturday! I'll report back....

rasbury

So why would the gimbal cause the issue anyway?

212rowboat

rasbury said:

So why would the gimbal cause the issue anyway?

have you ever dropped a clutch too quickly in a car and stalled it?  or, have you ever ran a lawn mower into grass too much for it to handle in one pass or too low?  same concept... the crank isn't allowed to spin due to binding.  stops it cold. 

rasbury

Got it...but I'd think you would have some other stuff like grinding going on to point you in that direction?