A4 lagging in gear

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Gregoryulrich

Member III
The last 2 times I went out my engine seemed to be lagging while it was in gear. If I take it out of gear I can get the engine to rev high rpms. In gear it seems sluggish and after half throttle it seems not to want to rev higher even at full throttle. It doesn't exactly bog down. Forgive my ignorance but I'm new to inboard engine ownership so my terminology might be off but I'm thinking transmission or packing gland (wick?). Where the shaft exits the hull is what looks to be a compression fitting which is super corroded on the outside and has probably has never been serviced. Does the E27 have a reduction gear or is it direct drive? I don't see any moisture on the shaft after use. That packing gland is supposed to weep a little lubricating the shaft right?
 
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Afrakes

Afrakes

Sustaining Member
Exhaust restriction

Make sure that you do not have an exhaust restriction. Excessive back pressure is a possible cause of your symptoms. Moyer Marine offers an exhaust pressure gauge that taps into the exhaust flange to diagnosis this problem. Al Frakes, Port Kent, NY.
 
Afrakes

Afrakes

Sustaining Member
Under Load

Under load the dynamics change. I assume that you've eliminated the possibility of debris on the prop and shaft? Does the engine do the same thing in reverse? Go to the Moyer Marine site and see what info you get from them. There's a ton of experience over there as well. Al Frakes, Port Kent, NY
 
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Gregoryulrich

Member III
Yes it does the same thing in reverse. The prop isn't fouled and it spins freely when the engine is out of gear. Someone at the dock mentioned bearings but I think he was just throwing that out there as a suggestion.
 
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sailingjazz

Member II
Lagging Engine

If the prop turns freely the engine needs checked. The A4 needs 3 things to run Air, Fuel, and Spark. It takes more Air and Fuel to rev under load than under a no-load situation. If the motor won't run to rpm under load I would check fuel first. Are the fuel filters clear? Are the fuel lines kinked? Next I would check air, is the air filter clean and unblocked. I doubt that spark is the problem but if the timing was way out you could get the symptom you are seeing. If the motor is also hard to start, that could indicate spark / timing problems. You could also put your hand on the transmission after running in gear for a bit. If it is quite warm there could be a problem there but it is much more likely to slip (and let the motor over rev) than to keep the motor from revving. Just some thoughts. Good luck.
 
steven

steven

Sustaining Member
I had a power lagging problem in the 1200 - 1400 range that was eventually tracked to gunk in the fuel system repeatedly fouling the carb.

LAst winter replaced tank, fuel lines, filters; and (again) cleaned up carb. Now runs fine.

But of course similar systems can be caused by different things.
As others have pointed out, Moyer is the authority.
 
tenders

tenders

Innocent Bystander
These are classic symptoms of an embarnacled prop. When was the last time you had the bottom scraped?
 
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Bill Sanborn

Member III
How fast will it rev in neutral? I will still vote for exhaust restriction.

On mine, when the exhaust was restricted, it wouldn't go over 1400 in neutral.
 
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Gregoryulrich

Member III
No definite conclusions yet. I get the bottom cleaned monthly and I personally dove the boat and inspected the prop and had my diver do the same. The prop spins freely in neutral and it isn't bound up by any lines or kelp. My diver has mentioned my prop is not in great shape but I don't think that's contributing to what I'm experiencing.

I took it out for a sail last weekend and experienced the issues for the first part if my sail. Coming in it seemed ok. I was doing 5-6 knots at about 50% throttle. I had a similar problem with an air cooled VW bus which turned out to be a swollen fuel line and caused a flat spot in the rpms at around 2500 rpms. I need to feel the transmission and stuffing box to see if it's hot after I motor around for a bit. Then I'll check fuel delivery.
 
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Gregoryulrich

Member III
Exhaust restriction

It revs really high in neutral and the exhaust sounds like it's echoing around in the pipes. It's a pretty throaty sound.
 
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Gregoryulrich

Member III
sailingjazz said:
If the prop turns freely the engine needs checked. The A4 needs 3 things to run Air, Fuel, and Spark. It takes more Air and Fuel to rev under load than under a no-load situation. If the motor won't run to rpm under load I would check fuel first. Are the fuel filters clear? Are the fuel lines kinked? Next I would check air, is the air filter clean and unblocked. I doubt that spark is the problem but if the timing was way out you could get the symptom you are seeing. If the motor is also hard to start, that could indicate spark / timing problems. You could also put your hand on the transmission after running in gear for a bit. If it is quite warm there could be a problem there but it is much more likely to slip (and let the motor over rev) than to keep the motor from revving. Just some thoughts. Good luck.
Click to expand...


Timing is ok. It never needs more that 1 or 2 revolutions before the engine fires up. It seems to run roughly for a while before it's fully warm. I know the PO removed the thermostat because he said it was running hot. I have not replaced that yet.

I was thinking partial fuel restriction, partial air restriction or perhaps a thrust bearing somewhere along the line. I don't know too much about the dynamics of an inboard engine but I have rebuild from scratch several small engines and an air cooled type 4 engine so I know enough about what's going on inside the block to have a mental image.
 
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Gregoryulrich

Member III
Yes both (first two links were the same) symptoms are exactly what I'm experiencing. First link (I skipped to the end) sounded like rebuilding the carb solved it, second case was a stuck valve. When I get back from vacation I'll perform a compression test. Seeing as performance is better once the engine is fully warm a stuck valve seems likely.
 
Rob Salinas

Rob Salinas

Member II
How old is your exhaust system? You still can have a restriction somewhere in the system, and can still have what looks like plenty of water batching out the stern. The rubber hose fore and aft of the muffler can delaminate and cause a restriction, and under load pressure builds up and bogs down the engine, I believe by holding down your exhaust valves. You said it sounds throaty.I'm also leaning towards the exhaust end. Good luck, and keep us informed on your findings and progress. Pictures?
PS I understand it's common on Catalina's
 
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Gregoryulrich

Member III
If I remove the exhaust pipe from the manifold to test the engine under load will I get raw water shooting out? I won't run it long, I just want to prepare myself.
 
Afrakes

Afrakes

Sustaining Member
Exhaust removal

If you do get water squirting out then you will know you really have a problem. Water is usually injected into the exhaust gases further downstream. Do you have an exhaust stand pipe or Vetus type mixing arrangement? You should get no water coming out by disconnecting at the exhaust manifold regardless of what type you have. Al Frakes, Port Kent, NY
 
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