No Power from engine

[Onlinerandy]

Hello,

I just purchased a 1977 Hunter 30 (Cherubini) and the engine has recently been rebuilt, new prop and transmission was rebuilt, less than 100 hours on all.

Here's the situation, I can not get the engine over 1300 RPM and it will not power past 3kts. I also have a difficult time pushing her out of trouble...seems like there's no power.

I've heard that this could be the result of the wrong prop. Can anyone tell me what I good prop would be on this boat.

Specs: I have a Yanmar 2GM 12hp with (according to the docs provided by seller) 13"/17 pitch 3 blade prop.

Any help would be greatly appreciated.

 

[Ralph Johnstone]

Specs: I have a Yanmar 2GM 12hp with (according to the docs provided by seller) 13"/17 pitch 3 blade prop.

Your 2GM is closer to 16 HP (continuous output) and your prop "may" be a little overpropped. Our boats are similar and the original prop from the factory for ours was a 15X12 two blade. I had it changed to a 14X10 three blade. The prop was sized and manufactured by a big commercial shop so I'm hoping they knew what they were doing. Worked perfectly from the start.

Before getting into the big $$$$$$$$$ for a new prop, check out the engine throttle cables and any other related etceteras which may be causing a problem. Also check for black smoke from the exhaust.

I know the engine has recently been rebuilt but just for curiosity, you might want to check the mixing elbow for carbon buildup. If it's plugged, maybe the rebuild wasn't all that thorough.

 

[Onlinerandy]

Thanks Ralph,

I'm looking into those items in a few minutes...can't wait to get this figured out...it's one of the many things to be done on this boat!

 

[kito]

I have the same engine on my H30. Not sure what the stock size and pitch is but 17 seems high. I know Campbell Sailor sizes a 12 x 7 for a 3 blade prop for my boat.

 

[Onlinerandy]

Kito,

I thought the prop was a bit high, I am looking into the 12/7 prop. On another note, when I do push the throttle forward, there is a just a puff of dark grey smoke.

 

[woodster]

contact General Propeller and get them to size your prop needs...they are close to you in Bradenton Fl....

regards

woody

 

[kito]

Not sure about the grey smoke but maybe see if a prop shop can repitch your existing prop. I believe they can go up or down 2 or 3 pitches. Getting it repitched will at least tell you your on the right track on your speed and power loss. You can always use your repitched prop as a spare.

 

[Onlinerandy]

Hey thanks guys, I'm going to call General Propeller about a new prop and to maybe have this on re pitched.

 

[rardiH36]

Before you go the "it's the prop route", check out again Ralph Johnstone's reply.

It also seems to me that the under-performance that you are describing is likely something different ... more engine related. Yes, you could be over-propped, but a 13" prop isn't that big to cause the degree of power loss you are experiencing. Even though the engine was re-built 100 hrs ago, maybe the mechanic missed re-installing something correctly. Or the fuel flow is partially blocked. Or as Ralph said could be the mixing elbow -- if it wasn't replaced and actually is full of carbon deposits.

Maybe post your issue on SBO's "engine and propulsion" forum or "ask all sailors"? You'll get a wider audience than only on the Cherubini specific forum. Would be a shame going through the hassle of a new prop only to find it wasn't the solution.

Just a thought.

 

[kloudie1]

Too much prop for sure, but you have an engine problem as well, as Rardi noted. If it is not pouring black smoke continuously when you push the throttle forward, you have a fuel delivery problem. First I would suspect the throttle linkage. It may be something as simple as the throttle cable slipped in its clamps. I neutral you should be able to get the engine to rev to 3750 RPM as measured with an accurate tachometer, not the one that is in the instrument panel ( unless you know it to be accurate). If it can't get there and is not smoking heavily, you probably have a fuel delivery problem. Partly plugged filters or tank outlet or fuel line (kinked?).. or a bad fuel pump. an air leak in the fuel pump suction line, or a misaligned fuel rack in the injection pump or an improperly assembled governor. I don't think that a 2GM (13 hp) is the original engine in that boat.. many were supplied with a YM12 but a 2 GM would be a great re-power upgrade if that is what the owner did.

 

[Nom De Guerre]

To reiterate, the 13hp 2gm is not the same as the 16hp 2gm20.

And the gray smoke does sound like a timing issue. It's possible the mechanic forgot to re-install a shim.

If the prop wasn't changed, it's quite likely not the culprit.

 

[EdWard3]

smoke

Before getting into the big $$$$$$$$$ for a new prop, check out the engine throttle cables and any other related etceteras which may be causing a problem. Also check for black smoke from the exhaust.
.

What does black smoke signify?

 

[Onlinerandy]

Thanks for that advice, I'm going this weekend to get started. I'm in the process of building a service kit for the engine, I'll look things over and if need be I'll add the needed parts to the list!

 

[Onlinerandy]

Thanks for the advice!

 

[Ralph Johnstone]

What does black smoke signify?

Black smoke indicates that more fuel is going into the cylinder than there is air present to burn the fuel. Any partially burned fuel leaves the cylinder as carbon particles.

 

[seadaddler]

Mixing Elbo

Does it reach high RPM's in neutral and I would check out the mixing elbo,
my old 2GM20 gave me a problem once and after not finding the problem I
decided to unbolt the mixing elbo and than start the engine up and it ran good
with the elbo off and ran it a short time each time and than cleaned it and it ran better than ever.
Nick

 

[Blaise]

Check mixing elbow FIRST. If the elbow is clogged, the engine may have been rebuilt unnessarily. Black smoke is also a symptom of over fueling caused by over loading. Cast iron elbows normally last no more than 4 or 5 years. I would be willing to bet a lot that that is your problem. I had a stainless steel elbow made about fifteen years ago and it is still good. Light grey smoke is usually a sign of an overheating engine.

 

[ggrizzard]

Randy, I just replaced my mixing elbow. If you think that's the problem, I suggest you remove the assembly in full. The threaded connector, the exhaust manifold connector (four bolts) along with the elbow in one piece, as my mechanic said that on units that old, the stainless threaded connector can break, jam and generally screw up your life big time.
You will be able to inspect the elbow with it still attached to the other parts. The other idea was to check the water injection nipple that is on the elbow. It will clog up before the elbow.

 

[EdWard3]

Where does one find a mixing elbow? And what is a ballpark cost? Is this something I can do myself?

 

[Ralph Johnstone]

Where does one find a mixing elbow? And what is a ballpark cost? Is this something I can do myself?

You'll probably regret asking for a ballpark cost as shown below for a Yanmar 2GM20F

They can only be had from your local Yanmar dealer.

They're not difficult to replace but check the archives here for some pointers.