Houseboat Outboard Engine - which motors, top speed, and gas mileage?

by Gene Abbott
(Columbia, SC)

Houseboat Outboard Engine Performance for House Boats

Houseboat Outboard Engine Performance for House Boats

Considering houseboat outboard engines, and wonder which motors, top speed, and the gas mileage results we'll see if we change outboard motors?

We own a 12 x 48' Aqua Cruiser houseboat, and it currently has a 115 Mercury outboard motor that needs to be replaced.

We're looking at a 75 hp Honda 4 stroke, but are wondering if this motor will push this houseboat.

Any advise would be appreciated. Gene

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Reply - Answer
Well Gene, welcome to the houseboat forums, and sorry to hear about having to replace your Mercury outboard :(

You are curious if a 75 hp four stroke outboard engine will push your houseboat, and the answer is yes, however you may notice a slightly lower top speed.

Now let's look at some of the difference between the two motors. The 115 hp Mercury had a slightly bigger diameter propeller than the 75 hp. And the 115 hp outboard will have a slightly more pitch on its prop compared to the 75 hp.

In reality, to push a houseboat hull through the water, it requires a lot less horsepower than people think. But to get the last 10% increase in top speed, really requires a big jump in engine displacement (or HP).

Now if I remember rightly, the Aqua Cruiser hull is a catamaran hull, that has a certain amount of lift when reaching top speed, you may end up realizing a 10% drop in cruising speed.

Will you get better gas mileage, yes, as I am guessing your Mercury was likely a 2 stroke, and the newer 75 hp Honda is a 4 stroke (better efficiency) and there is claims of up to 40% better fuel consumption.

There are some houseboat owners that have already done some outboard engine re-powers, and they may be able to post some of their numbers, testing, or real life performance results to help you in the decision.

Lastly, hopefully some of our readers will share and post comments about their houseboat outboard engine performance experiences. Feel free to use the "Click here to post comments." link found near the bottom of this page.

Thanks again for sharing, IAN from all-about-houseboats

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Comments for Houseboat Outboard Engine - which motors, top speed, and gas mileage?

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Mercury 115
by: Dennis

Ian is correct about prop diameter and pitch, very important factors to consider when selecting an outboard motor. I recently restored a 1980 Kayot 12x36 steel pontoon houseboat that was formerly a rental boat on Lake Mead (Nevada). The original motor was a 1980 Johnson 90 hp 2-stroke.

When I purchased the boat, the motor was shot so I didn't have any baseline performance to compare with when deciding on repower options. I found a great deal on a low-hour 2014 Mercury 115 hp 4-stroke outboard.

I started with a 14x10p prop. This prop worked fine but I was not happy with top speed. I changed up to a 14x13p (the highest pitch and diameter option for this motor) and achieved a decent cruise speed of 8 miles per hour.

While I'm not setting any speed records I remind myself I'm pushing around 15,000 pounds (the equivalent of two dually pickup trucks) with a mere 115 hp. I went with a little more horsepower to allow extra power for towing a small boat or two personal watercraft.

The best part: According to the Mercury Smartcraft multi-function engine monitor gauge I'm getting a fuel consumption rate of about 2.3 gallons per hour at about 3,100 RPM.

I'm super happy with the 115 and glad I didn't go smaller, very fuel efficient and acceptable cruise speed. Also enough power for braking and maneuvering in marinas and around the docks.

75 HP Honda
by: Anonymous

Don't know how old this thread is, but we have the same boat (12x48 Aquacruiser) which we bought used and it came with a 75HP Honda outboard.

We have only taken the boat out once in non-windy conditions to have some work done, and the motor pushed fine and we crossed the lake at a nice cruising speed.

We don't plan to take ours out though unless necessary, we have a great view of open water at our marina so our boat is to be a floating condo...

But some have told us a higher HP motor might give us more control if we were out on the lake and battling wind. Someone else said too much HP would drive the front end down.

Another person said a boat that size should have twin outboards. Everyone has an opinion though and I don't have any real knowledge on the subject other than the experience of cruising the lake on a calm day with the 75HP motor and being a satisfied passenger.

Mercury outboards
by: Jon Scotts

I have to go with Mercury here!

Thanks, Jon

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