M25 stalls...need advice

woodster · May 25, 2014

Jwhy said:
It was running a little rough a week ago and didn't want to rev very high. Yesterday it stalled at low rpm but started right up again. Today it ran for an hour at 1800 rpm, then stalled at low rpm. It would restart but wouldn't rev and then quit right away. Filters were changed about two months ago.
Any ideas?

is your exhaust elbow clean........... or clogged maybe

Stu Jackson · May 25, 2014

Exhaust elbows do not exist on M25 engines on these and other Catalinas. They are different than Yanmars. The exhaust system consists of an exhaust RISER which is a 1 1/2" or 1 5/8" insulated pipe that connects to the rear of the engine manifold to carry the hot exhaust gas to the water lift muffler. The now hot exhaust raw water from the HX is introduced into this pipe close to the muffler, and then they are pumped overboard.

Filters:

Doesn't matter when you changed them, check them again. I'd take the primary off first and see what it looks like. You could just as well have changed it yesterday --- check it again.

You could have bad fuel in the tank. Have you ever had your tank cleaned?

You could also still have the fuel pickup screen still at the end of the pickup hose inside the tank. Your profile doesn't indicate the year of your boat, but I'm figuring early to mid 80s.

This topic includes a lot of M25 engine information, please read it all (Critical Upgrades):

http://c34.org/bbs/index.php/topic,5078.0.html

Our C34 Tech wiki has a great deal of M25 series engine information as well:

http://www.c34.org/wiki/index.php?title=Diesel_Engine

I believe you could have a nasty fuel problem. Don't waste $$ on fuel "polishing" -- it's snake oil. Remove the fuel from your tank and check it out. You can use a 5 gallon yellow jerry jug and disconnect your engine electric fuel pump and pump it into the jerry jugs to see what it's like.

As Critical Upgrades suggests, it could well be the screen on your pickup tube.

Or you could still have your fuel pump BEFORE the primary filter. Take the bottom of it off and clean the filter on it.

In order:

1 - check the pump filter and replumb the primary/pump
2 - check the primary filter
3 - if it's clean, check the pickup tube to see if the dumb screen is still there, if so, pull it out
4 - bleed then start the engine
5 - if it doesn't work, come back here

Good luck, let me know what happens next and we'll continue to try to help.

rgarrison@gmail.com · May 26, 2014

great analysis, thx from everyone!

Anonymous 121765 · May 27, 2014

JWHY,

The guys have offered all the necessary tools for solving your problem.

The only other option I can ad, is that at some point when you know you have a clean tank w/o sludge etc., feel free to get rid of the pickup tube screen. I don't know how many times having similar problems with stalling, I would check the screen & there was that grey sludge clogging my fuel flow especially throttling up. Cleaning my screen would cure it. Until that is, it clogged again over time. That led to adding an access plate to my tank then hand cleaning it.

I had asked around whether the screen was really needed. The comments I received was 50-50. If you buy good diesel & use it, your tank should stay pretty clean & your primary & secondary filters should do the rest.

I'll probably take a hit for this but, I never use microbe killing additives. This has worked well for me here in Florida. Whatever bugs may be in your fuel, having a closed recirculating system, any fuel not burned by the injectors will flow back to your tank. If the injectors don't cook-em on the first pass, you could get em the next time around. I don't want them to die in my tank, sink & sludge up the bottom.

If using the proper grades of diesel, you shouldn't need lubricating additives. If having far too much water in your tank, this is another subject to discuss.

CR

MH · May 27, 2014

My 89 has the filters in this order. 1 electric fuel pump. 2.Racor. 3. Screw on filter. Is this in the wrong order?

weinie · May 27, 2014

MH said:
My 89 has the filters in this order. 1 electric fuel pump. 2.Racor. 3. Screw on filter. Is this in the wrong order?

1 & 2 should be switched

Brad Woodward · May 27, 2014

Being that the engine will start and run at medium RPM but not at idle doesn't sound like a fuel pick up issue but rather a pressure issue. I would check your lines from the injector pump to make sure there is no leaks. The pump is where the three file fuel lines come from the top of the engine to the cylinders. If even the slightest leak you are loosing pressure in one injector and you will have idle/power problems. Sounds more to me like you have an injector problem than a fuel supply one.

jimmcgee · May 30, 2014

Brad,
Sorry but this is EXACTLY how my engine was acting when the fuel pickup screen was clogged. The blockage starves the engine for fuel and it acts like a badly clogged filter.

When I pulled the pickup tube I couldn't believe the engine had run at all with that much gunk in the pickup.

I'm a big believer in the KISS method when diagnosing engine problems. Start with the easy stuff first. Pull the tube, clean it and discard the screen, then replace both filters and fire her up. 90% of the time you'll cure the problem.

I'd also drain some fuel out of the bowl on the primary and see if there's growth or gunk in it. That'll tell you if you need to polish your fuel or clean out your tank.

Jim

Blakem · May 30, 2014

If you find sludge/biologic crud in your tank/filters...

Try one of the desel-#2 Fuel oil additives that includes mostly Ethylene glycol monobutyl ether (sometimes called glycol ether, but thats improper). The product is transdermally toxic (poisons you righ through your skin) and is toxic to about every living system.......but....... it works to disperse water and ice and kill the fungus and bateria that inhabit desel fuels.

I get this stuff at 100% concentration (Aviation - Prist fuel additive www .pristaerospace.com ) and add enough to a small gas can enough to make a 0.1% concentration in my main fuel tank, add some fuel, shake well and pour into the main tank. Use gloves!

Let mix stand in the tank and come back in a few hours and that black muck will start turning grey. Takes about a day to get full affect - will suspend some water and will kill whatever is growing in the tank.

My expierience is with an O'Day 30 / Universal M-18 boat up on the hard for ~3-4 years with bad o-rings on the fuel filler. I got most of the standing water out of the tank via mechanical means, but still had lots of crud in the tank. Added the right amount of EGME, had the boat slung into the water and came back the next day to a much improved fuel situation.

If you are not a pilot/aircraft mechanic or know one who can help you out, the 2nd best souce ~60% EGME is "Sludge be Gone - SBG" made by FPPF (www .fppf.com) and available at most real Plumbing/Heating suppliers. NOT BLOWS, HOME CHEAPO, Etc.... you have to go to the one the real techs use.

This stuff works and its cheap as one quart will treat 500 gallons or so of fuel.

Trust me, Im a engineer!
Blake
O'Day 30, 1980 Project

Lindcat · May 30, 2014

One commonly overlooked problem in the fuel delivery system is the screen in the base of the electric fuel pump. If your fuel pump is receiving fuel prior to your Racor and spin-on, that would be an area of concern. Lindcat

Brad Woodward · May 30, 2014

Jim, a friend of mine had that problem too, but his symptoms were the engine would start and run great for 10 minutes then it would die. He got home in 10 min runs with the sail but little wind. Guess we have given him just about everything there is to look at. Hopefully he will get back to us & let us know what fixes the problem.

Stu Jackson · Jun 1, 2014

Jwhy said:
So should I reroute the lines so the racor filter is between the tank and fuel pump?

Please read the links in Reply #3, answers your question.

You said you ordered a fuel pump? From where? What did you order? You could have gone to a Napa auto store and bought one.

Stu Jackson · Jun 8, 2014

Glad to hear you solved the problem. Glad to help. The next time you hear of someone with this problem (since it happens so frequently!

), send them to this link!

You have removed your wiring harness trailer connectors, right?

Stu Jackson · Jun 8, 2014

I don't know, you'd have to ask Napa, but there are Options.

http://c34.org/bbs/index.php/topic,2515.0.html, please read both pages.

M25 stalls...need advice

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

Attachments

.

.

.

.

.