Engine cutting out under load

[LakeErieFishing]

Another topic - I'll briefly explain the symptoms then all the actions taken so far. It's a Merc 888 (302 Ford). Engine starts fine. Idles fine, purrs like a kitten. However, once warm and especially under load and higher RPMs (above 2,000) the engine bogs down then cuts out. It will restart but won't let you throttle up. Limps back to the dock at under 1,500 RPM.

Here's what I know. Electronic ignition module is good (new). Ignition coil is good (new). Cap and rotor good (not many hours, look new). Have not checked ignition switch and wiring (this could be the issue but I'm asking other opinions).

I don't think it's a fuel system issue. Carb has been rebuilt. Fuel pump is good/new. Fuel lines all good and clear. New fuel filter. New gas only in tank, old gas was siphoned out. I don't think it's a fuel delivery or carb issue unless the float is out of whack.

The issue feels electrical to me. Suggestions?

[ITD]

Take it out, run it until it bogs, then unscrew the gas cap, if you hear a sucking noise your vent is plugged. It sounds like a fuel issue to me, starving for gas.

[cessnaair]

Friend of mine had similar symptoms, he was hitting trim switch at same time and that was taking voltage from ignition shutting it down

[LakeErieFishing]

The vent hose we think is clear. Nothing blocking the openings on the fitting, and the hose is in excellent shape. We'll blow through it just to be sure.

Right now we suspect the ignition switch is creating the issue. That and/or the wiring that runs from it back to the engine. We thought about bypassing the ignition switch (hot wire the engine to start it). Or, just replace it (they're cheap).

It's the original ignition switch (43 years old). I restored a 1973 Searay 22' SRV. Gutted it like an eggshell. New transom, installed (cut) pressure treated stringers/bows, oak engine mounts, new floor, cuddy (etc.), re-gel coated the hull, new engine box, etc. It's better than when new and looks beautiful. Way better structurally. It just needs to run :)

[LakeErieFishing]

Hot wire to test to see if the ignition switch is the issue. Not permanently, just to test :D

[winni83]

Had something similar happen to my Sea Ray with a 260 Mercury. Turns out that the fuel line made one or two turns from the tank to the engine. Ran fine for a while and would then cut out. One of the fuel line attachment brackets was in a poor position and as the line warmed up, it would crimp the fuel line. Then after a while it would run fine, only to happen again. Simple fix after a lot of investigation was to adjust how the fuel line was routed from tank to engine.

[LakeErieFishing]

The fuel line from the tank to fuel filter seems fine (newer, no obstructions). The fuel line from the filter and pump to the carb has no kinks and no leaks around any of the fittings. It looks fine. It doesn't act up until it gets warm, and the warmer it gets the more it acts up. This feels electrical to me, like something is shorting out or arcing due to the heat caused in the electrical system after the engine has been running awhile and especially under load.

[winni83]

My fuel line looked good too. The only way the issue was picked up was that as it began to cut out,we raised the engine hatch and saw the crimped line. After it cooled down a little, the crimp disappeared.

[LakeErieFishing]

Was the crimped line a rubber hose-type line?

[Descant]

Reading your description of symptoms, I immediately thought fuel. I have seen a bad coil give similar symptoms, but you have replaced it.
If the ignition switch is 43 years old, then I'd guess the fuel tank is that old too. While you have replaced the fuel, that doesn't mean there isn't sludge in the tank that interferes with fuel pick up. When you used less fuel, at idle, below 1500 rpm etc, everything is fine. When you accelerate, the fuel that is in line runs the engine OK, but then, reduced fuel flow causes the engine to bog down. When you reduce demand (slow down) the clogged fuel system can keep up with less demand. I agree with the thought that an electric fuel pump could exhibit some of these symptoms if it isn't getting steady electric feed, but not my first suspicion. Either way, it sounds like a fuel problem, not ignition. In a car, I've seen a clogged air filter give similar problems, but the flame arrestor on a boat should be OK in this regard. Is there a safe way to use an alternate fuel supply and not draw from the built in tank?

[winni83]

Yes it is a rubber line. My mechanic took the boat out with me and he was the one that figured it out by looking in the engine compartment as soon as it started to happen. Until then he was stumped.

[LakeErieFishing]

Descant, fuel tank was replaced when I rebuilt the stringers and flooring. After we drained the gas this spring I looked into it with light and nothing unusual in regards to particles at the bottom of the tank. Fuel pickup tube was clear that goes into tank. It's also about 1/4" off the bottom. I can easily blow into the line that goes from the tank to the fuel filter and hear it bubble. I'll double checking the air vent line but it appears clear.

The fuel pump is mechanical and new this year. It's not the fuel pump.

The engine stutters then dies after it gets warm, and especially when rpm's get above 2,000. It can be running great for 5 minutes up on plane, then it losers power and quits if you don't back off the throttle. Even then it will quit if you don't shut it down and let it cool. It will restart but you usually have to let it cool for awhile to restart it. The more it runs, the longer you have to let it cool before it will restart. This all appears to be electrical to me, not fuel system.

[LakeErieFishing]

We can try an alternate fuel source but the engine is acting wacky only after it gets warm. We've been told by a few folks that electrical issues can cause this to happen. Maybe it is fuel delivery but there is a definite correlation between the engine and electrical system getting warm and the issues popping up.

The coil is good, the electronic ignition module is good. The spark plug wires and primary coil wire from the distributor are older wires, at least 20 years old so that might be part of the issue (arcing when they warm up). The ignition switch and wiring could also be causing the issue when those wires get hot - so others have advised.

At this juncture we will triple check the fuel system to make sure the vent hose is clear and the fuel line isn't collapsing. Also, might go ahead and change plug and distributor to coil wires. I can hot wire the engine to by pass the ignition switch. I don't like doing that but if the switch or wiring is the cause that will show it.

Suggestions beyond how I intend to trouble shoot?

[SIKSUKR]

Sounds like a fuel delivery issue. As was posted earlier, run it till it happens again and open the fuel cap to see if it has a vacuum. If you're not sure, then try to loosen the cap to let air in without letting water in to at least prove/disprove this.

[LakeErieFishing]

I'll give it a try (taking gas cap off) and let everyone know.

[Orion]

.......
The fuel pump is mechanical and new this year. It's not the fuel pump.
.......

Never rule out new parts as being the problem. One time I spent 4 days trying to diagnose an issue after having recently replaced ignition components, swearing that they were new and couldn't be the problem......they were (bad condenser).

It does sound like fuel to me as well.

[Rich]

The fuel pump is mechanical and new this year. It's not the fuel pump.


Here's a mildly related story... which happened to me.

I had a car that did the same sort of thing. When cold, it would run fine. But when warmed up, it would lose power and sometimes I couldn't start it again if I shut it off until it was stone cold.

We checked everything that you can think of. It seemed like it wasn't getting any fuel, so we replaced the mechanical fuel pump.

The problem continued, so I ended up solving the problem at the time with an electric fuel pump. This seemed to solve the issue, and we couldn't find out why the mechanical fuel pump would stop pumping fuel when the engine was hot.

One day when I had nothing to do, I decided to try to find out why the replacement brand new mechanical fuel pump did not solve the issue.

I removed it and analyzed it very closely to fully understand how it worked. It was a very simple device, so I couldn't understand how it wasn't working when the engine was warm. As long as the pushrod that was activating the mechanical fuel pump was pushing in on the pump's lever, then it had to work. There was no way that it couldn't function when warm if the lever was being depressed.

That was the clue! This car had well over 170,000 miles on it (closer to 200,000). I removed the pushrod and found a replacement, mostly as a comparison as the end of the original one seemed to have a bit of wear on it. It turned out that the old one was just a bit shorter than the new one due to wear (it probably wasn't getting enough oil, or was a bit softer than it should have been, perhaps due to a manufacturing defect).

Evidentially, over the many miles, the push rod had some wear on it. And as the engine warmed up, some tolerance would change due to the heat, which would cause the mechanical fuel pump to not pump the fuel because the push rod that activated wasn't pushing fully enough on it's lever.

At the time, the replacement pushrod cost me about $5 to replace.

I replaced the old pushrod with the new one, and was able to remove the electric fuel pump.

So don't just think that because you replaced the mechanical fuel pump that the problem is solved. You still need to verify that the engine is getting enough fuel when it's warmed up and under load.

I can't tell you how many hours we spent trying to find the source of this issue.

[LakeErieFishing]

Where could I find the pushrod, or even know the part needed for my engine? It's a merc 888 Ford 302 early mid70s vintage.

[TiltonBB]

Not sure if I read it here.

I had a fuel line with an inner liner that looked good on the outside but the inner liner was collapsing and restricting the fuel flow. I had similar problems to the OP and after replacing the fuel line they disappeared.

[Blue Thunder]

Another topic - I'll briefly explain the symptoms then all the actions taken so far. It's a Merc 888 (302 Ford). Engine starts fine. Idles fine, purrs like a kitten. However, once warm and especially under load and higher RPMs (above 2,000) the engine bogs down then cuts out. It will restart but won't let you throttle up. Limps back to the dock at under 1,500 RPM.

Here's what I know. Electronic ignition module is good (new). Ignition coil is good (new). Cap and rotor good (not many hours, look new). Have not checked ignition switch and wiring (this could be the issue but I'm asking other opinions).

I don't think it's a fuel system issue. Carb has been rebuilt. Fuel pump is good/new. Fuel lines all good and clear. New fuel filter. New gas only in tank, old gas was siphoned out. I don't think it's a fuel delivery or carb issue unless the float is out of whack.

The issue feels electrical to me. Suggestions?

Ford electronic ignition of this vintage (EEC II, III & IV) were notorious for bad modules and would cause exactly the condition you describe. How new is the module and was it new or reman?

BT

[Dave R]

Ford electronic ignition of this vintage (EEC II, III & IV) were notorious for bad modules and would cause exactly the condition you describe. How new is the module and was it new or reman?

BT

Yup, the notorious "thick film" ignition module.

[LakeErieFishing]

Blue thunder, ignition module is NEW (not a rebuild) and 2 weeks old. Pertronix ignition module, drop in replacement. Engine starts good and runs smooth with new module. It started and ran with original equipment module, but not smooth like now.

This could be a fuel system problem. The fuel line setup is as follows - aluminum fuel tank, excellent shape. Pickup tube looks good and pickup end is situated roughly 1/4" from the bottom of the tank. A rubber fuel line (about 14 years old) connects the pickup to the fuel filter (spin on "looks like an oil filter" type). Metal line runs from filter to the fuel pump (looks good, no kinks, wear, etc.) New metal line (no kinks, etc, no obstructions) runs from the fuel pump (it's a NEW mechanical fuel pump) to the carb. Carb was rebuilt in May. The choke could be sticking, or maybe the float is not setup correctly, or other. I'm open to suggestions.

Should I replace the rubber line from the tank to the fuel filter? Very easy to do, and it's possible the inner part does have deterioration (??).

[LakeErieFishing]

I'll add the spark plug wires are at least 20 years old. Not sure if they're arcing or of the distributor to coil line might be faulty. I do know when wires heat up they can create issues if they're not intact end to end.

[Blue Thunder]

I'll add the spark plug wires are at least 20 years old. Not sure if they're arcing or of the distributor to coil line might be faulty. I do know when wires heat up they can create issues if they're not intact end to end.

I'm not the type of person that just throws parts at something until I solve the problem, but in this case, a 20 year old set of plug wires would seem like a good place to spend a few bucks....

[Blue Thunder]

Yup, the notorious "thick film" ignition module.

If he's running Pertronix ignition Dave, that's not a Ford system. It's a system for converting points and condenser to electronic. My 87 Liberator had the so called "Thunderbolt Ignition" in it. My father in law used to love to tease me about the name....but I digress....

[HellRaZoR004]

Try fixing the engine overtemp issue first and see if this still persists.

[LakeErieFishing]

If he's running Pertronix ignition Dave, that's not a Ford system. It's a system for converting points and condenser to electronic. My 87 Liberator had the so called "Thunderbolt Ignition" in it. My father in law used to love to tease me about the name....but I digress....

I'll explain - the original distributor (all of it) was replaced with electronic ignition, a prestolite electronic ignition system. Prestolite no longer is in that business. Pertronix makes the ignition module replacement for the prestolite electronic ignition. It's a drop in replacement.

[LakeErieFishing]

Try fixing the engine overtemp issue first and see if this still persists.

I'll work on the overtemp issue. It's possible the water circulating pump is bad. It doesn't leak, but that doesn't mean it's not working right. I am going to remove the thermostat to see if that helps the issue. That's not a final fix, but it might tell me something.

[Rich]

Where could I find the pushrod, or even know the part needed for my engine? It's a merc 888 Ford 302 early mid70s vintage.

I don't know. This particular engine may have the fuel pump driven directly from a cam lobe, instead of a push rod that rides on the lobe of a cam.

My example wasn't to say that a push rod was worn, but to say, just because you replaced the fuel pump itself, unless you measured the fuel pressure output from the pump, don't discount that there would be still be issues with a part that you replaced. Of course it's very rare, but a new part could somehow also been faulty.

Good luck with your problem, I hope you let us know what the final fix is when you find it.

[Descant]

Despite the fact that I've been leaning towards fuel, BT's mention of the ignition module reminded me that I had a similar symptom/problem once with a 5 liter Mustang (302 cid) so it was plausible. New module was a quick fix.
I don't know much about this, but I recall stories of fuel system problems from one end of the boat to the other when Ethanol was introduced. Sounds like you've replaced almost everything but that rubber fuel line. Is this a possibility?
Despite OP's frustrations, this has been an interesting thread. Thanks for letting us all participate and for giving good feedback.

[HellRaZoR004]

Are you sure the timing is correct? I also just read somewhere that if this is off it could cause overheat conditions...something else that you are seeing.

http://forums.iboats.com/forum/engine-repair-and-maintenance/mercruiser-i-o-inboard-engines-outdrives/55776-cooling-problem-302-mercruiser-888/page2

[SAB1]

Yikes. It could many things as discussed above but the guy who recommended new plug wires is spot on. That's a cheap thing to do that takes minutes. I'd try that before I did anything else. Twenty year old wires aren't doing u any favors.

[LakeErieFishing]

Are you sure the timing is correct? I also just read somewhere that if this is off it could cause overheat conditions...something else that you are seeing.

http://forums.iboats.com/forum/engine-repair-and-maintenance/mercruiser-i-o-inboard-engines-outdrives/55776-cooling-problem-302-mercruiser-888/page2

No, I don't know if the timing is correct. I found timing marks and will check the timing.

[Descant]

There are several youtube videos on timing. You need a timing light.
https://www.youtube.com/watch?v=Wwp9rtTPPJc

[LakeErieFishing]

There are several youtube videos on timing. You need a timing light.
https://www.youtube.com/watch?v=Wwp9rtTPPJc

I have access to a timing light. However, I don't think the timing "teeth" shown in the video are on the motor.

[Frdxplorer]

We just had a very similar problem. Turned out that it was a battery issue. Although it was starting fine, both batteries were extremely low. Replaced them, and now totally fine.

[LakeErieFishing]

If a fuel system problem, what type of fuel line do I need that runs from the fuel tank pickup to the spin-on fuel filter? Is a rubber or vinyl hose okay? The fuel lines from the fuel filter to carb are all stainless.

Thanks

[ITD]

If a fuel system problem, what type of fuel line do I need that runs from the fuel tank pickup to the spin-on fuel filter? Is a rubber or vinyl hose okay? The fuel lines from the fuel filter to carb are all stainless.

Thanks

Best bet is to go to a marina or autoparts store and by fuel line, bring a piece of what you want to replace to get the right size.

[LakeErieFishing]

I have access to a timing light. However, I don't think the timing "teeth" shown in the video are on the motor.

Okay, I found the timing marks. I bought new plug wires. I'll time the engine at 600 to 700 rpm and see how it goes.

[LakeErieFishing]

Best bet is to go to a marina or autoparts store and by fuel line, bring a piece of what you want to replace to get the right size.

3/8" marine grade fuel line. I'm getting some of that too. I'll replace the current line.