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Tiller

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Those three are all pretty good.

I would do two things. Phone around and ask for the price and availability of a particular part. Like an exhaust elbow or Engine water circulating pump (not the raw water pump) or something kind of common and you would expect to replace maybe one day in the distant future. That will give you a good feedback on price of parts and if they are easily obtained.

Second thing is write down the specs. Now this part may not seem important, but actually for a small engine it is. Because you have to think about not only powering the boat through the water, but at the same time, can it Run say a freezer, and Alternator and still push you into a Headsea if it has too.

Hp is important, but what many manufacturers don't tell you is what the Hp is measured in. BHp, SHp, SAE, DIN, Continuose, Max Intermitent etc etc. which can make a huge difference in the specs between each other. So find that out and write it down on paper so you can see which is what against each other. Just for instance there, my Perkins can sometimes get sold as a 130Hp engine. But that is a Max intermittent rating. In reality, the continuous SHP is only 90Hp. That is a majorly big difference.

The next is Torque, although not really quite so important for a small motor. In a nut shell, Torque and Hp combined is where you get your "Power" in an engine. More modern engines like the Volvo high pressure rails which are computer controlled injection etc, have a very flat torque over a very wide rev range, giving good hard work over a big rev operating range. Some motors you have to rev the guts out of them to get the power, even though they are the same Hp rating as another. Personally, I don't like Volvo engines though.

Then combine those figures to weight. Depending on your boat design, you may or maynot need to worry toomuch about weight. A Cat would mean as light as poss. A keeler it wouldn't really matter too much.

And finally, Rev range. In my opinion, the lower the revs the better. Less screaming noise, less vibration, and in the end, longer life "usually" if all things are equal. The large Yanmars are light weight, high reving, high power engines. Designed to be used in Planning hulls for performance. That comes at a cost to it's life time. But smaller yanmar are not quite like that, so may not be an issue.

And I guess like most of us, price is a major yard stick to judge things by. But not somuch the more expensive the better it is. In this case, the cheaper the better it is.

Hope that helps.

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Consider if you have better access to one side of the engine than the other.

If you can get at the portside easier, the engine with the filters and injector pump on that side is going to be far better bet for maintenance.

Also the one that fits nicely into the proposed engine box is going to stand head and shoulders above a unit that needs to be squeezed in because it is 30 mm taller/longer.

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Thanks for that. weight is a major consideration. Looked at an old lister because i could hand start it but at 600kgs its a little heavy almost 1/6th of all up weight. Can get extra 10 HP for 12kgs with kubota.Want to be able to steam at 7+ knots.

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