Problem with engine stalling at low RPM after running fine for quite a while

[RIDAVIDK]

Hello all

It's been quite a while since I posted anything here. I had a different boat for the last 5 years, but am now working on getting my old 1975 Pearson 28 with atomic 4 running well again.

As background the boat in question has been sitting on the hard for at least 2 1/2 years, unmoved. I started working on it about a month ago and have it back in the water. I'll list the chronology of events and work done to it.

I changed the oil in the engine and started it. It ran ok. I had to move the boat to a new mooring about 3 hours away and headed out. After about 1 hour the engine died. 15 minutes later I was able to start it and made it the rest of the way at lower rpm's than I had been running it. It seemed to run fine until it died.

Since then I've pumped out all the old gas and put in 10 gallons of fresh 93 octane gas and some sea foam. I changed the spark plugs, changed the fuel filter, pulled the carb off and cleaned it. It has run well for the last three outings until yesterday. I've been leaving the motor running while sailing as kind of a test. After about 3 hours we headed back to the mooring field and as I throttled down the engine sounded like it might die. I throttled up a bit and it came back to life. I attached to the mooring ball, put it in neutral and returned to idle speed and it died fairly quickly. I was able to start it again after a few minutes.

I'm in Newport harbor with some very expensive boats around me and live in fear of the motor dying while surrounded by many very expensive yachts. Any suggestions would be appreciated greatly. I recall I got some good advice when I sought it many years ago for the same boat.

Sorry this is so long.

[Dave Neptune]

info

Did you check anything when it died?

Don't bother with 93 octane, the A-4 will make more power and run better on regular 87 or LOWER octane if you can find it.

Need some info on the engine too, type of fuel pump, type and age of ignition, the C-advance condition and spark color. Are the plugs fouling or are they a creamy chocolate color? Where is the idle air screw set and have you adjusted it while the engine is running? How is the fuel pressure?

Dave Neptune

[Mo]

Agree with Dave. Something else to consider is continued dirt making it's way into your fuel system. Although you cleaned the tank, new fuel etc it only takes small particles flaking off from the tank or lines to affect the jets. Something to consider...might be worth putting an inline filter and remove and clean up the carb again.

[Al Schober]

If you don't have an inline filter, you need one. If you have a old filter, it should be changed. Many filters have internal steel parts which corrode (water/moisture in the fuel) and send rusticles to the carb.

[RIDAVIDK]

By an inline filter are you referring to a small round filter just before the carburator? I did put a new Racor type filter in as part of the process of trying to get it running better. That would be located after the fuel tank and before the fuel pump.

The fuel pump is mechanical, the ignition is electronic and I'm not sure of it's age but I would say at least 10 years old. Not sure what the "C advance condition" is. The plugs are new and I haven't pulled one out to look at it and won't be able to until this coming weekend at the earliest. Not sure how to measure the fuel pressure. I did play with the idle speed a bit and set it at what seemed like a good rpm. No tach so I don't know what it is.

I have considered that there might be bad stuff still in the fuel tank. Not quite sure how I would clean that out. I had purchased a second racor type filter and may replace that again.

The engine ran great for probably 3 hours, but when I reduced the rpm at the mooring field it seemed to struggle a bit although I managed to keep it going until I got on the mooring.

Thanks for all the suggestions so far.

[Mo]

If you had pumped out the fuel tank and cleaned as best you can I'd say you are done there. In the past we'd add some more fuel following pumping, rock the boat, and pump dry again. That said, it's hard to do it without the tank removed and with some boats that just isn't a viable option. So if you don't have an easily removable tank suggest repeated tries on adding fuel, slosh it around and pump it out.

The inline pump is just a metal car in line fuel filter. Mine is between my wall mounted electric pump and the carb. Seems to work great as I've rarely had fuel issues since doing so in 2007.

When cleaning out the carb I generally take it all apart carefully and blow out the jets with air. If I cannot see through a jet after blowing it out with air I use a small wire strand to open it up. Usually can carefully take the carbs apart without ruining the gasket if it hasn't been put together with gasket cement...a no no on your carb.

Centrifical advance. That's under the distributer cap. You remove the cap with all the wires attached and gently move to the side. If you have short wires you may have to pop some off, but generally it's an easy proceedure. There's a plate at the bottom of the distributor....points, condensor or EI is on it...remove, remove plate and there may even be a dust cover under there. Remove that, ... if the springs are intact and not seriously rusted lubricate them with some oil. I use Rust Check or Fluid Film. I don't use WD40. You want a good lubricant on them. I'd even use motor oil on them over WD40. If they look really rusty I'd consider ordering a set from MMI. Generally you would want to lube them on a fall maintence schedule every year. What that does is give you peace of mind and also ensures your distributor cap doesn't get corroded on....use the same oil on cap bolts. Nothing worse than needing to take the cap off and everything is torn up and siezed.

I don't deal with fuel pressure gauges. I keep an electric pump spare on the boat. I can see a benefit for people that have mechanical pumps and Dave and a few more could help you with setting up a fuel pressure gauge if you think you need one.

[RIDAVIDK]

Thanks for the suggestions. I've ordered the inline fuel filter kit along with an extra spare filter.

[sastanley]

I am with Mo and vote on lubing and cleaning the advance weights. If you have not pulled the distributor cap in 10 years (because you went to electronic ignition), or even a few years from the boat sitting, they can stick and the springs are not strong enough to pull them in when crusty and the engine won't idle. I popped mine out and cleaned and lubed them on a seawall in Cambridge, MD mid trip a few years ago. It is easy to forget about them when you no longer have points to service after a switchover to electronic ignition.

[RIDAVIDK]

I will give the advance weights a cleaning and lube the next time I'm at the boat. Thanks to both of you for the suggestion.

[sastanley]

ridavidk, One of the other things we preach on the Moyer forum is try to do only only one big change at once. If you change 5 things we do not know which one was the actual fix. Review the thread and proceed at your discretion.

[tenders]

Sudden deaths are good indications of electrical problems; sudden deaths when hot, and starting again when cool(er), are classic symptoms of a failing coil.

Inside that coil cylinder is a winding of zillions of loops of very fine wire coated with thin insulation - and heat encourages that insulation to break down once it gets old and brittle.

If you don’t know how old your coil is, I’d suggest just replacing it with a Moyer coil so you know it’s the right one. I would not/do not mess around with other coils with varying degrees of internal resistance, etc.