My 52' has a Perkins 4236 engine, recently tuned. I'm concerned that the engine is not performing as it should, and would to know what other Irwin 52 owners have experienced. Here is performance data recently taken while motoring in a river, with light wind, no tide or current: RPM Wind Sp SOG 1.5 2.0 5.7 1.8 5.0 7.0 1.8 7.3 7.0 1.8 2.0 7.1 2.0 6.6 6.9 2.0 9.1 7.2 2.0 7.4 7.3 2.0 3.9 7.4 2.1 6.2 7.3 2.1 8.1 7.4 2.2 Maximum engine RPM Any information would be appreciated. Thanks, Ken Hammer
Perkins Engine Performance
- Thread starter Ken Hammer
- Start date
- Status
performance, engine? or Prop!
Your numbers look to me more like a prop that's either undersized or incorrectly pitched. I've got a Perkins 4-154 (original) in my '77 I42 and have changed props a time or two. On my Moondance a big 3-blade 18X18 pushes me along at hull speed just about the time I hit max sustained rpm of 3,000, but the 3 blade drags like a sea anchor. With a 2 blade sailor prop (also 18X18 I am never close to hull speed under power, plus the vibration and cavitation limit my max comfortable rpm to 2,700. Someone I trust has said that for a 2 blade I need a 17X15 to reduce hull slap and allow the smaller blades to bite. He said that while the smaller will increase efficiency and reduce vibration, I can't expect hull speed without 3 blades with a boat as heave as mine. My alternatives are 1) 3 blades and sail slower, 2) 2 blades and motor slower, 3) fold or feather to get more prop surface in the water with less drag. Perhaps, in your case also, it's not the Perkins it's the prop. Skippermoondance
Your numbers look to me more like a prop that's either undersized or incorrectly pitched. I've got a Perkins 4-154 (original) in my '77 I42 and have changed props a time or two. On my Moondance a big 3-blade 18X18 pushes me along at hull speed just about the time I hit max sustained rpm of 3,000, but the 3 blade drags like a sea anchor. With a 2 blade sailor prop (also 18X18 I am never close to hull speed under power, plus the vibration and cavitation limit my max comfortable rpm to 2,700. Someone I trust has said that for a 2 blade I need a 17X15 to reduce hull slap and allow the smaller blades to bite. He said that while the smaller will increase efficiency and reduce vibration, I can't expect hull speed without 3 blades with a boat as heave as mine. My alternatives are 1) 3 blades and sail slower, 2) 2 blades and motor slower, 3) fold or feather to get more prop surface in the water with less drag. Perhaps, in your case also, it's not the Perkins it's the prop. Skippermoondance
- Status