Lister Blackstone SL2M

[Fish53]

Hi, I have a Lister Blackstone SL2M 8.5hp @ 1800rpm, 2 to 1 gearbox turning a 16 in. three bladed propeller. I also have a displacement hull that, with engine and all other equipment would weight about 5000 lbs. with a 26ft water line length. I would like to get opinions on how others may think this will work out. The intended use would be canals and occasional lake and coastal use fishing and cruising. I love the engine and it's in excellent shape so I'd like to get some use out of it. Thanks.

 

[Jcorstorphine]

Hi there,
I have run a quick calculation on your engine / boat / prop combination.

With the engine at full throttle i.e. 1800 RPM your 16 in prop is correct but it should not only be 16 in diameter, it should also be 16 in Pitch.

This will give you in flat water just over 5 knts and provide a bollard pull of 300 lbs.

Seems ok for inland but not too sure how it would be for open sea conditions with wind waves and tides. As an example, my father had a 26 foot heavy lifeboat conversion with 20 HP @ 3000 rpm and 2:1 gearbox. I have run a calc on that combination with a 14 x 10 prop and get a speed of just over 6 knts and a bollard pull of 512 lbs. I have to say, there were many days when we had a job to make very much headway against a combination of wind and waves but it was a heavy boat and did not have a fine entry shape at the bow.

 

[Fish53]

Thanks for the info, I'm not sure if 5kts and limited ability in open water sounds sufficient. I also have a BMC 1.8, which seems to going in the other direction of having more than I need, but most people seem to lean on the side of more is better.

 

[Jcorstorphine]

You could always fit the listet as a wing engine.

 

[Fish53]

It weighs over five hundred pounds and is physically quite large, I'm not sure I'd have room or be able to compensate for the off center weight. It would be nice however to have a hand start emergency engine.