Power issues

[sallyjane823]

I have an Atomic 4 gasoline 30 HP in my 1976 Ericson 27 sailboat that I bought 1 year ago, believing the engine had been recently rebuilt with about 800 hours on it. Now I am having power issues under load, ie maximum 2000 rpm. I was getting 3200 rpm at full throttle a year ago. Carburetor has been cleaned, new spark plugs and fuel filter. My mechanic diagnosed "excessive crankcase pressure (evidenced by blow-by) caused by worn oil control rings". He said no compression check was necessary because he is sure about the problem and that solving this problem means essentially an engine overhaul. Does that sound right?

[Administrator]

Clean prop?

Bill

[ndutton]

Questions that come immediately to mind, some of which you may not know the answer:

• Direct drive or reduction gear engine?
• What size prop, diameter and pitch?
• Was the timing checked? That's a loaded question because I bet the mechanic has no idea how to accurately check the timing on an Atomic 4. Timing can have a big impact on blowby.
• Is there a PCV system installed?
• And yeah, I'd like to know the compression too. I bet a lot of us would. Mr. mechanic's refusal is a red flag to me.

[indigo]

Something is fishy for sure. To the best of my knowledge, the Ericson 27 came with a direct drive A4. In order to get the kind of RPM you were seeing then:

A. It does indeed have a reduction gear
B. Your tachometer is off by perhaps a factor of two
C. Your transmission is slipping miserably
D. You have one very small prop

Do you know what the boat speed is in both scenarios?

+1 to Neil regarding the compression check. Any mechanic worth his salt would want to make that check.

Tom

[lat 64]

Just the statement ""excessive crankcase pressure (evidenced by blow-by) caused by worn oil control rings" is not correct. Oil control rings control.....oil!
Compression rings control...Compression. Worn or stuck compression rings cause blow-by—worn oil rings let oil up into the top cylinder.

If the mechanic wants to impress you with specific causes, He has to do more specific investigation. It's a flag to me too. Proceed with a jaundiced eye on his work.

It may be true that the engine is worn out but the investigation is not complete.

Often these engines suffer from lack of use and that can be manifested in things like stuck rings and rusted parts.
Many of our forum members have seen fit to go through a simple resurrection of a "tired" engine that goes on to run well.
A complete compression test in controlled situation and then attempt to loosen up stuck rings is WAY cheaper than a new engine.

Russ

[Ram41662]

Sally, I gave you my two bit in the other thread you posted this in. As I said there, and these guys all seem to agree, not doing a compression test is just wrong.

[JOHN COOKSON]

SJ823
The problem may not be with the engine at all! You may have blockage in the exhaust system.
My advice is the same as others - ditch this "mechanic" pronto.

TRUE GRIT

[Dave Neptune]

A plugged exhaust will also drastically increase blowby as well as timing.

Dave Neptune

[CajunSpike]

I just had a guy help me try to get mine motor started for the first time. He claimed to understand the motor well.

After doing nothing but running down 2 batteries, just cranking and not wanting to do a compression check, he gave up.....

Later, I replaced the carb. Properly adjusted the points.
Cleared a coolant blockage. Found a stuck valve that freed up upon running.

Now the motor runs fine.

Check what you have before believing its bad.

Its also possible the prop may have gotten something tangled in it, causing spin resistance.

[tenders]

I agree with Bill first and foremost - the easiest explanation for a diminished max RPM is a fouled propeller, plain and simple. Rule that out first.

Secondly, and do this almost as immediately, never talk to that mechanic again. He is just making stuff up to try to scare you into hours of fruitless labor charges.

You can get a compression tester from Harbor Freight and do a perfectly competent job yourself in 30 minutes, including the time spent Googling how to do it.

But I think your problem is propeller-related until proven otherwise.

[Administrator]

...never talk to that mechanic again. He is just making stuff up to try to scare you into hours of fruitless labor charges.

You can get a compression tester from Harbor Freight and do a perfectly competent job yourself in 30 minutes, including the time spent Googling how to do it.

+1.

Bill

[joe_db]

Originally Posted by lat 64

Just the statement ""excessive crankcase pressure (evidenced by blow-by) caused by worn oil control rings" is not correct. Oil control rings control.....oil!
Compression rings control...Compression. Worn or stuck compression rings cause blow-by—worn oil rings let oil up into the top cylinder.

If the mechanic wants to impress you with specific causes, He has to do more specific investigation. It's a flag to me too. Proceed with a jaundiced eye on his work.

It may be true that the engine is worn out but the investigation is not complete.

Often these engines suffer from lack of use and that can be manifested in things like stuck rings and rusted parts.
Many of our forum members have seen fit to go through a simple resurrection of a "tired" engine that goes on to run well.
A complete compression test in controlled situation and then attempt to loosen up stuck rings is WAY cheaper than a new engine.

Russ

The A4 will NEVER have excessive crankcase pressure because the crankcase is not sealed

[joe_db]

Originally Posted by indigo

Something is fishy for sure. To the best of my knowledge, the Ericson 27 came with a direct drive A4. In order to get the kind of RPM you were seeing then:

A. It does indeed have a reduction gear
B. Your tachometer is off by perhaps a factor of two
C. Your transmission is slipping miserably
D. You have one very small prop

Do you know what the boat speed is in both scenarios?

+1 to Neil regarding the compression check. Any mechanic worth his salt would want to make that check.

Tom

^
THIS

On any kind of sailboat with anything remotely close to a correct prop, no one is getting even 3,000 RPM. The only way I can do that is in reverse.

[alcodiesel]

I can get 2200 rpm on my boat, clean bottom and prop. Tops. Note: same boat as orig. poster.

Another "mechanic" bites the dust. Everybody's an expert around my marina.

[ndutton]

2600 RPM WOT. Direct drive, 10x8 fixed 2 blade prop, hull and prop cleaned monthly, precise timing, carb rebuilt within the past two years, fuel filter replaced within the past year.

[lat 64]

So,
The list of possibilities is(in no particular order of likeliness):

• Prop fouled,
• collapsed exhaust hose,
• stuck compression rings,
• ndutton's{Neil) list,
• indigo's(Tom) list,
• Worn out engine and the mech was right

Take this list and check all items before dropping big do$h on a overhaul. As you can see, this gang is confident you can get more data all on your own. If you own an A-4, then you should know an A-4. We always recommend getting the manual from Moyer's and READING it from cover to cover. If you have any doubts about the quality of the answers you are getting here, then you should understand this group that answered you already are a mix of qualified and experienced A-4 owners in machine tooling, racing, electrical, A-4 parts retail, and even shade-tree style. All of this info is good.

Cheers,

Russ

[lat 64]

Originally Posted by lat 64

...As you can see, this gang is confident you can get more data all on your own. ...

I meant, with our help you can get lots of answers. It sorta sounded like I was saying "figure it out yourself". Not the case. We love to help! We're more than happy to figure this out.

BTW, see if you can post a few pictures of the engine setup; exhaust, final drive, etc.

[joe_db]

Originally Posted by sallyjane823

I have an Atomic 4 gasoline 30 HP in my 1976 Ericson 27 sailboat that I bought 1 year ago, believing the engine had been recently rebuilt with about 800 hours on it. Now I am having power issues under load, ie maximum 2000 rpm. I was getting 3200 rpm at full throttle a year ago. Carburetor has been cleaned, new spark plugs and fuel filter. My mechanic diagnosed "excessive crankcase pressure (evidenced by blow-by) caused by worn oil control rings". He said no compression check was necessary because he is sure about the problem and that solving this problem means essentially an engine overhaul. Does that sound right?

This part just hit me - My grandmother is a better mechanic than that and she is dead Kind of like a doctor going "well only one thing causes headaches, you must have a brain tumor, we'll do a head transplant right away"
First big question: Is the boat slower? Maybe something changed with your defective tach because odds are about 0% you are getting 3200 RPMs.
First suggestion - get a compression tester and check it yourself.
Second one - get a vacuum gauge.
We can talk you through enough tests to get to the bottom of this.