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06/11/2007 09:53:35 AM
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Len
Junior Member
Posts: 6
Joined: 06/10/2007
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I just purchased a 1985 Coastal 38. It originally had twin 350 IO's which was converted to a single 115 Merc Outboard. To compensate for the loss of ballast, they added concrete slabs to the engine room. I am not interested in achieving planeing speed, but the 115 seems way too inadequate. The boat yaws all over the place and is slow to respond to steering. I am considering maybe putting on a 200 or 225 outboard, or a single diesel v drive. Other options are twin outboards.
Anyone have any experience or suggestions?
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Laughing Gull
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06/11/2007 09:13:56 PM
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johnplatou
Admiral
Posts: 340
Joined: 10/18/2002
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Len
I would look at twins in the range of 50 hp each, provided they
have high thrust gear cases with the biggest dia. props avaialable.
My best guess for adding economy for my HM 38 is my stock 300
hp Mercruiser for planning 25/30 mph (1.1/1.3 mpg) and twin
high thrust 9.9 4 strokes for slow speed cruising (6/10 mpg) @ 3 to
4 mph
It's hard to get a HM 38 over about 8 mph without a huge amount of
power. It takes about 300 hp to plane.
I have done some tests on mine and determined that 3 hp will get
about 2 mph without wind, 25 hp will get you about 4.5 mph (prop
was ventilating) and 5 mph with a 40 hp.
Diesel would be best for fuel economy, but you have have to cruise
a very long way to pay for it.
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Johnplatou
1990 HM 38 with Mercruiser 454 Bravo.Lift Stored, Trailerable, and Fits in garage. One of 9 boats presently owned. Boating experience 45 years and 8000 hours. Trailering Hm 38 16 years and 6000 miles, other trailering 100,000 miles and 39 years.
Edited: 06/11/2007 at 09:14:51 PM by johnplatou
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06/12/2007 08:07:45 AM
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Len
Junior Member
Posts: 6
Joined: 06/10/2007
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Thanks, John,
This gives me a place to start. I bought my 38 from a young man who lives in New Port Richey, FL, about 15 miles up the IOC from my place north of Clearwater. He owned the boat about a year and totally re-did the interior, but the exterior nees a lot of work. It was apparently in quite rough shape when he got it.
I picked the boat up and ran it down to my place on Memorial Day weekend. It was pretty windy, and it was a bear to steer, with the boat yawing all over the place. It prop was cavitating badly, which got me thinking about what I could do to improve the situation. I had particularly wanted outboard, because IO's do not live long in salt water.
The prop is an aluminum 13 pitch and I am soliciting advice on what I could do about that to improve the situation. Yesterday, I put on a hydrofoil (cavitation plate) and will see that offers any improvement.
If I can get the boat to turn and steer well and cruise 5 - 6 knots, I will be happy.
The concrete parking bumpers they put in in the engine room to compensate for ballast bug me, and I plan to eliminate that, by filling one unsued 70 gallon fuel tank with water and adding a gas generator.
I did an NADA lookup on the 115 Merc. It is a 1987, and is only worth about 400 bucks, so if I have to get something else, it will not be any big loss.
Len
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Laughing Gull
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06/12/2007 08:50:18 PM
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johnplatou
Admiral
Posts: 340
Joined: 10/18/2002
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The hydrofoil should help. If you can get a tube prop
guard would be of great help. Simple lowering the engine
deeper is the water could help. Cupping the prop would help
also.
The 115 had a 2:0 to 1 gear ratio. The 85 had a 2:3:1.
Use a 2:3 to one with the biggest dia prop with the most
blade area cupped. Could be fabercated at the local prop
shop.
Call me if I can help 832 473 8928
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Johnplatou
1990 HM 38 with Mercruiser 454 Bravo.Lift Stored, Trailerable, and Fits in garage. One of 9 boats presently owned. Boating experience 45 years and 8000 hours. Trailering Hm 38 16 years and 6000 miles, other trailering 100,000 miles and 39 years.
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06/23/2007 11:32:27 AM
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enginetamer
Member
Posts: 87
Joined: 02/14/2007
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This is a cool topic, because it seems to be a common complaint among many houseboaters. the yawing tendancy at low speeds, I mean. some of the more experienced hands have been sympathetic to the newest owners, but it may be a pervsive problem. I realize that the value of outdrives/outboards is maneuverability at low speeds and in close quarters, but steering comfort over time is often reported to be a fatiguing problem.
I hear that the latest "HOUSEBOATING" magazine has a presentation about thrusters. Is it possible that an inboard rig with assist from thrusters is the best of all Worlds in the houseboating game? Any comments or observations from those skippers using that kind of rig?// Paul
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lookin' for adventure and the next wild engine!
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