See full version: Signs That Your Outboard is Mounted Too Low
Unless you’re extremely familiar with a specific boat’s hull, it can be difficult to know whether or not your outboard motor is mounted at the right level. Most boat owners have dealt with this problem at one point or another, but it’s surprisingly difficult to find good information to solve it.
We got some input from the experts to create this quick guide to checking your outboard’s height. It’s never a perfect science, but there are some very simple ways to put you on the right track.
Fortunately, there is usually one reliable indicator to tell whether or not your motor is close to the correct mounting height. This indicator is your anti-cavitation plate and its position in relation to your hull. more
More the area of the outboard underwater more will be the drag. This suggests that the outboard is too low.
Depending on the condition of your boat, your outboard may need a change of height. These signs are given below:
Your new boat may come with power pre-installed for optimized performance. However, in many cases, dealers mount the outboard as it comes uninstalled.
What is a good rule of thumb on where to mount enging heightwise?
Just had center tube added to boat. When they remounted the engine the mechanic said on most all pontoons the cavitation plate should be about 1 inch below the bottom of the tubes. Originally mine was mounted in the second hole from the top and he changed it to the top hole to lower the engine about 1 inch.
However, the new center toon projects about 1.5 feet farther out the rear from the boat than the other. And because there is a slight downward angle when the boat sits in the water (rear of boat heavier than front) The engine seems to sit considerably lower in the water. My biggest concern is that when I unload the boat from the trailer with the engine down, the water line while unloading (boat at ramp angle) is up on the cowling (cover,, right word??) It is still below the piss hole.
“If you are 250 RPM low, say about 5700 but you want to get to 6000, raising the motor a hole might get you there, and produce about one additional mile per hour in top speed,” said Greenwood. “Or if you are already at 6000, raising the motor may allow you to move up one increment in prop pitch to stay at 6000 but go faster.” here
Propeller diameter also can affect the ideal engine mounting height. Switching from a small-diameter prop like a 13.5-inch Mercury Laser II to a 14.5-inch Mercury Enertia effectively lowers the swing of the prop blades by a half-inch.
[links]
“I would say that on a significant majority of the new boats I see the outboard motor is mounted too low,” says David Greenwood, who in his role as product planning manager at Suzuki Marine tests and rigs dozens of boats each year. “At least it’s lower than necessary, because most boat builders are very conservative and to be fair, they have no idea how their boat is going to be propped, loaded, and used after it’s sold.”
Adjusting the mounting height of an outboard on the boat transom can affect performance and every boat can be different, so actual on-water testing is best.
There are quite a few variables in play when considering optimal engine height on the transom. A key factor is how far aft the propeller is located from the bottom of the boat. Water flowing from under the boat rises so if the prop is further away from the transom, it may be possible to mount the engine higher. All outboards are different in this regard. For example, a Mercury Verado positions the propeller about six inches further aft than a Mercury OptiMax outboard. A boat rigger’s rule of thumb is that the motor can be raised one inch for each eight to 10 inches of distance between the transom and prop. As the prop moves further aft, it’s also likely to be in cleaner, “harder” water, and be more efficient. This is one reason performance boaters use a set-back device between the boat transom and the motor bracket.