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post #1 of 8 Old 10-18-2008 Thread Starter
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Prop Size Bahama 30

Anyone have the size (12 x ?? LH) for a two bladed prop on a 1978 Islander Bahama 30 with the original Volvo MD7A 13hp diesel engine? Mine had an oversized three bladed prop when I got it. I replaced it with a Campbell Sailor two bladed but I'm not happy with the lack of speed under power (maybe 5 knots on a flat surface). I've had this prop re-pitched a number of time but can't come up with a happy medium, too much cativation when it gets pitched too much. I'm thinking of going back to the standard two blade but don't have the pitch.
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post #2 of 8 Old 10-29-2008
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The 2-blade fixed prop on our 1980 Bahama 30 (with Volvo MD7A) is 12" x 14" x 3/4" LH. The boat powers pretty well, about 6 kts. in flat seas.
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post #3 of 8 Old 10-29-2008 Thread Starter
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Prop Size

Thank you! I've never been able to reach 6 knots, even down hill, under power. What RPM have you got the MD7A running at to get that speed?

Last edited by bvermeer; 10-29-2008 at 02:29 PM. Reason: mis spelled word
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post #4 of 8 Old 10-30-2008
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We get 6 knots at 2300-2400 RPM max. With only 13 HP, any headwind or seas will slow us down pretty quickly. Also, keeping the bottom clean seems to make a big difference in powering speed - a couple weeks of growth makes a noticeable difference.
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post #5 of 8 Old 10-30-2008 Thread Starter
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Prop Size

Thanks. I'm on the hunt for a replacement. That's the general RPM I cruise at and I've been lucky to get to five knots on flat water. Time for a change.
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post #6 of 8 Old 10-31-2008
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Differences in Bahama 30 Props for different years

Now that's interesting. I bought a 1984 Islander Bahama 30 a month ago and there less in common here than I would have expected. It has a 15 HP Yanmar 2GMF with a 2 blade 13 x 10 right-hand prop on a 3/4" shaft. I wonder when they changed?
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post #7 of 8 Old 10-31-2008 Thread Starter
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Prop size

Interesting. I suspect that the original engine has been replaced with the Yanmar. I've seen that happen more than once. I'm just surprised that they would have retained the 3/4" shaft. Most opt for the standard 1", having to replace the strut and stuffing box. Most mechanics suggest that the 1" shaft is need to handle the extra torque of the 18 hp. But then, I've never seen a shaft bent due to the extra hp of a new engine. I've actually thought of going to a saildrive when I replace the old MD7A. It'll be easier to install and reduce the vibration at the same time. We'll see....
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post #8 of 8 Old 01-13-2009
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Bert,
have not been lurking here for a while, lots going on. We traded thoughts on hard starting MD7A's a while back. You probably already know, if the compression is not up to snuff, you will not get the HP no matter what size prop. I adjusted my valves a year ago, and don't think I get the same speed as before, so I think they might be a little sloppy. I might have a real mechanic redo them, but I think the rings are probably the problem.

Unfortunately our old beasts are just getting tired!

Kent
B30 Jazzed
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