I recently purchased a 1985 Hunter 34. The engine would start to smoke at about 2800 rpm and then stall. It would run all day at 2500 rpm. I read that lack of air causes black smoke. The air filter was clean amd no rags or dead rats in the intake. I opened the engine hatch and discovered that under full load (15 x 15 prop) I could get 3200 RPM and it would rev to 3800 RPM with out a load. Where is the air supply vent for the Hunter 34. I have a small vent in the starbard side but a previous owner had installed a deisel generator and it is used by a fan to blow air to the generator. This was the only opening that I can find that might have supplied air to the engine and I am not sure that it was supplied by the manufacturer. What was the design intent to supply air to the deisel engine? Has any one else had a problem? What is the Cure? All answers appreciated, even smart allec ones. Charlie
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Marc Honey
Hood scoop!!!
Just kidding about the hood scoop. From all the posts I've read on this site I'd suspect clogged exhaust/mixing elbow problems. Seems weird that opening hatch would give more rpms. My 28.5 doesn't seem to have any special vents to supply air and my 2cyl. Yanmar performs flawlessly.Stand by, you'll probably get more advice than you dreamed of soon... this is a great web-site!!!
Just kidding about the hood scoop. From all the posts I've read on this site I'd suspect clogged exhaust/mixing elbow problems. Seems weird that opening hatch would give more rpms. My 28.5 doesn't seem to have any special vents to supply air and my 2cyl. Yanmar performs flawlessly.Stand by, you'll probably get more advice than you dreamed of soon... this is a great web-site!!!
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Derek Rowell
Engine starvation
Wow! That's a strange one! My '83 H34 has no problems like that at all. Here's a suggestion to try. In my aft cabin there is an access opening for rear engine/coupling access. The cover has a finger hole (about 1" diam.) for removal. Remove the mattress and run the engine and determine whether or not (1) you can detect any air flow through the hole, and (2) whether covering the hole creates a vacuum and starves the engine. You could also make yourself a simple U-tube manometer from inexpensive clear plastic tubing filled with water to measure any air pressure drop in the engine compartment. On my boat the engine compartment liner is cut away under the stuffing box to allow drips to go to the bilge. That would seem to be a natural ventilation source. Good luck Derek
Wow! That's a strange one! My '83 H34 has no problems like that at all. Here's a suggestion to try. In my aft cabin there is an access opening for rear engine/coupling access. The cover has a finger hole (about 1" diam.) for removal. Remove the mattress and run the engine and determine whether or not (1) you can detect any air flow through the hole, and (2) whether covering the hole creates a vacuum and starves the engine. You could also make yourself a simple U-tube manometer from inexpensive clear plastic tubing filled with water to measure any air pressure drop in the engine compartment. On my boat the engine compartment liner is cut away under the stuffing box to allow drips to go to the bilge. That would seem to be a natural ventilation source. Good luck Derek
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Paul
Air flow
I'm no expert on here, but many years ago I spent a summer working on a big private 60' sport fishing boat . When heading someplace swiftly (and this thing would travel at 30+ knots, the engine room access hatch was always left open. You could stand next to it and feel the air being sucked past you The only downside was the noise, yet the owner was always in a hurry and didn't care, saying he could pick up 2 to 3 knots by opening the hatch.
I'm no expert on here, but many years ago I spent a summer working on a big private 60' sport fishing boat . When heading someplace swiftly (and this thing would travel at 30+ knots, the engine room access hatch was always left open. You could stand next to it and feel the air being sucked past you The only downside was the noise, yet the owner was always in a hurry and didn't care, saying he could pick up 2 to 3 knots by opening the hatch.
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Jim Oursler
Black smoke probably mixing elbow
Look up SMOKE as a keyword search in the Forum Archives and you will find the solution and a lot of reference to clogged mixing elbow in the Yanmar 20 HP, which can be removed and soaked for 30 minutes in 2:1 muriatic acid to remove clogs. ALSO ..us 34s are now in BIG BOATS..so come on over from mid sized. Regards, Jim
Look up SMOKE as a keyword search in the Forum Archives and you will find the solution and a lot of reference to clogged mixing elbow in the Yanmar 20 HP, which can be removed and soaked for 30 minutes in 2:1 muriatic acid to remove clogs. ALSO ..us 34s are now in BIG BOATS..so come on over from mid sized. Regards, Jim
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David C.
black smoke
I never had the black smoke problem on my 34 that we put about 7,500 miles on, but I know of one instance thwt about drove a poor guy to the funny farm before someone figured out what was going on. Seems any time he tried to get above 1800 rpm the the black smoke started rolling and the engine simply wouldn't put out any more. When he opened the lid on the engine compartment the engine ran fine. The problem turned out to be loose insulation. When the lid was down on the compartment the insulation would hang down in front of the air intake on the diesel. Anything over 1800 rpm would cause the loose insulation to be sucked into the air intake.
I never had the black smoke problem on my 34 that we put about 7,500 miles on, but I know of one instance thwt about drove a poor guy to the funny farm before someone figured out what was going on. Seems any time he tried to get above 1800 rpm the the black smoke started rolling and the engine simply wouldn't put out any more. When he opened the lid on the engine compartment the engine ran fine. The problem turned out to be loose insulation. When the lid was down on the compartment the insulation would hang down in front of the air intake on the diesel. Anything over 1800 rpm would cause the loose insulation to be sucked into the air intake.
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Jorge Cela
Return Fuel Line Closed
I had similar problem with my recently purchased 29.5 and I could go all day with 2000 RPM's or so, but as soon as I will increase the RPM's to 2800 the engine will produce black smoke and in a few minutes will die. The mechanics left the return fuel line closed after changing the fuel pump. In my boat the return fuel valve is located inside a covered opening in a storage compartment on port side, next to the top of the fuel tank on the port side. Hope this help you. Jorge
I had similar problem with my recently purchased 29.5 and I could go all day with 2000 RPM's or so, but as soon as I will increase the RPM's to 2800 the engine will produce black smoke and in a few minutes will die. The mechanics left the return fuel line closed after changing the fuel pump. In my boat the return fuel valve is located inside a covered opening in a storage compartment on port side, next to the top of the fuel tank on the port side. Hope this help you. Jorge
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