lowering motors?

[leeroychristison]

Hi everyone, I have a 15.5 ft fibreglass boat with a 60hp 2 stroke merc. Was wondering what effect lowering the motor one bolt hole would have on boat performance etc. Cheers

[Fortunamate]

it will raise your bow until you hit plane

[leeroychristison]

what about those hydrofoils, they any good, trying to get a better ride in the chop and hopefully better fuel economy?

[jawz12]

a guide line is,when the boat is on plane,the cavitation plates should be at or slightly above the water.look at the engine with the boat on plane,is this what you have ?? lowering the engine can and will cause the boat to porpoise,and it increases drag,slowing the boat down,increasing fuel consumption,it creates additional drag,also makes the steering "heavy"...
hydra foils,a product i do not reccomend.if the boat's difficult to plane,be sure the engine is propped correctly for the application.run the boat,normally loaded,read what you get for max rpm,compare that number with the mfg's specs,if you're below that reccomended number,you're overpropped.using the correct pitch prop greatly improves the ride,and it will drop the time to plane,as well as save you fuel money...

[leeroychristison]

Thanks for the info Jaws. The boat runs sweet as it is, was just looking for ways to get further on a tote tank. Guess I'll just have to cut down on the plethora of gear I lug with me.I had heard that hydrofoils can increase mileage by up to 30%, but found that hard to chew. Scanning the internet it seems that there are more negative outcomes than positive, so I'll leave the boat as is. Cheers

[aloop]

I have a tiller 25hp Merc with Dolphins and the boat jumps out of the hole to plane quick. I raised the bolt on the engine, when I tried it I thought I would get thrown out of the boat, kind of makes it unstable.

[gradyfish265]

Hydrofoils on outboards do little to increase performance themselves...if there is a gain it is because the running angle has been changed to one that is better suited for that hull, that is where the gain comes from, not the foil itself. The foils cannot provide lift for the hull...that is created strictly from the hulls speed, shape, and weight. Tilting the engine does the same thing, but smaller tiller engines cannot do this. The only added benefit to the foils is that on bigger heavier boats you can hop on plane a little easier or you can stay on plane at a lower speed. Some guys with smaller outboards with power trim tilt use them instead of adding trim tabs to save money, and they work ok, but do not have the same control, and they are putting a strain on your engines honestly. The alternative, and correct method is get the right prop or add trim tabs, depending on what is needed for the application. The correct fix is more expensive and many like to take the cheaper method to fixing this problem, but often in the end you do more damage or end up doing it the right way down the road and just wasted money the first time around. Typically boating manufacturers mount engines too low in the water if anything, very rarely do they put them too high from a factory...only if repowered and requested to go that high, or if the engines are being tweaked for higher performance would the engine already be mounted too high. As Jaws states, you should see the cavitation plate roughly level with the waterline, if the spray covers it and you cannot see it, raise the engine, you will see an improvement in efficiency more then likely.