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Old 26-05-2010, 10:51   #1
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Indifferent Engines

I'm looking at a 1995 37' Lagoon with indifferent engines...Perkins 18hp & 27hp...bigger engine, don't know model, was installed in 1998. I assume the plan was to upgrade the smaller engine at a later date. What are the disadvantages of this setup? I am new to cats.

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Old 26-05-2010, 11:03   #2
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Well you could end up going round in circles

Guess you have a choice, either take it for a spin and see how much of a problem it is, or plan on changing one of the engines or even both to sort it out properly. Trying to balance the power from the two engines is going to be difficult and what did they do about the props? still on the original ones or are they different too?

What other lash ups are on board? tread carefully and keep back lots of cash to sort it out properly. Afterall one day you might won't to sell it and who is going to buy it like that.


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Old 26-05-2010, 11:10   #3
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Lock the helm for a straight course, bring the revs up to maintain that course, and if neither engine is overworked, you don't have a problem.
so many projects--so little time !!
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Old 26-05-2010, 14:29   #4
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If the 18 and 27 hp engines have the same transmission and props then the boat should go straight with the throttles set to the same RPM on both. The 27 hp will loaf a bit and the 18 hp will work harder. Nothing wrong with that.

So center the helm and rev up both engines to the same rpm and see what happens.

If the 27 hp engine has a lower gear ratio or a prop with more pitch then it will be working about as hard as the 18 hp engine and the boat will need some offset helm to go straight. Not a big deal either.

FWIW, my Island Packet Cat 35 had two 27 hp Yanmars and was not overpowered. That may be why the PO decided to upgrade one and presumably the second later.


Can you ask him?

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Old 26-05-2010, 18:07   #5
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Check to see if there are any asymmetrical applications on the 27hp engine. Some lagoons also do things like hi output alternators on one side, or an engine driven watermaker. I know of one that has to run the port engine in order to run the windlass.

Fair Winds,
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