130 SPORT with 40-HP

[Lakedays]

I bought a 2005 130 SPORT with a Mercury 40-HP FOURSTROKE engine. I am disappointed in the available power with two adults and two children aboard. I suspect the propeller needs to be changed. The current propeller is a black Mercury 10-3/8-inch-diameter 14-pitch. The gear ratio is 2.00:1.

Acceleration at full throttle from a standing start to plane is a struggle. The engine only accelerates to about 4,600-PRM. The boat speed has not been measured; the boat speed may be around 22-MPH. This operation is al an elevation of 5,100-feet above sea level.

Give me advice on what propeller should be used.

[Phil T]

With elevation comes reduced atmospheric pressure and combustion engines suffer performance degradation.

Electronic fuel injected motors experience less drop than carburated engines.

At 5100 ft above sea level you loose 6.1 horsepower. The 40hp is now a 33.9 hp engine.

The Black Max 14 pitch came with the engine/boat from Boston Whaler.

While the 130 Sport of that era was not a stellarly fast at sea level with a 40hp engine, in your location it is a bit of a dog.

To help offset the elevation, you should lower the pitch of the prop. I would estimate a 12-pitch of the same make and model of propeller would help. Note the boat's top speed will not increase.

The only way to gain speed would be to replace the engine with more horsepower. A 60 or 70 would bring you back up to to the upper 30-MPH boat speed.

[Lakedays]

Thank you Phil.

This morning I was doing more reading and noticed the new SPORT 130 boats with a Mercury 40 come with a four-blade 10.1 x 14 SPITFIRE propeller.

Q1: What’s your opinion on that?

Q2: Would that be better or worse than a 10.3 x 12?

[Phil T]

I would want to verify the gear ratio of the current Mercury 40 is the same. They occasionally change.

The new 130 SuperSport is heavier than your model.

I would try the Spitfire in that lower pitch I suggested.

[NorthShoreWhaler]

I had the same boat. It’s small and weight distribution helps a lot to get on plane. Put the kids in the bow to get on plane and that should help. We all had to lean forward but it worked. I went to a 4 blade prop and that helped hole shot as well. We were able to pull a tube and even ski behind it but that’s at sea level.

[Lakedays]

Took it for a cruise last night after work. With myself (180-lbs) and my six-year-old son (50-lbs) the GPS SOG hit 26-MPH on a smooth lake at engine speed of 5100-RPM.

I hope a [new] propeller can get the boat speed to 30-MPH by [letting the engine accelerate to a higher speed], and [the new propeller will create'] better planing to pull the kids on double skis.

[With the propeller in use] now I don’t think [the 130 SPORT with 40-HP] could pull my six-year-old or my ten-year-old

I am a little disappointed. In retrospect I should have bought a classic [13-footer].

[Lakedays]

Gear ratio according to the sticker on the drive says 13 x 26 2.00:1

[Lakedays]

I went to a fouir-bladed propeller...

Q3: what size and pitch propeller?

[NorthShoreWhaler]

Quicksilver Nemesis 12 pitch. Part number 8m8027511

[jimh]

In order to allow the engine to accelerate to a higher engine speed, you have to reduce the load on the engine from turning the propeller. The only way to reduce the load on the engine by changing the propeller is to REDUCE the load created by the propeller, which means using a propeller of LOWER pitch.

Increasing the number of blades on the propeller to four from three will NOT reduce the load on the engine created by the propeller.

To increase the boat speed you need more power. A new propeller does not make the engine have more power. A new propeller may be more effective than the current propeller, but it can only cause a higher engine speed if the load from the propeller is reduced.

The concept that you can increase propeller pitch and simultaneously get more engine speed is not workable.

For pulling heavy loads like two water skiers, you need to reduce propeller pitch. In that situation a four-blade propeller might be helpful; a four-bladed propeller will have more blade area that a three-bladed propeller of similar diameter and individual blade size, but it will also be harder for the engine to turn. That's why you need to decrease pitch.

Note the suggestion above in which a 12-pitch propeller is being used.

Also, with small boats and low engine power, adding weight and load will often demand a propeller pitch change to get to optimum engine speed range at full throttle.

[Lakedays]

Installing a [four-bladed propeller of 10.375-inch diameter by 12-pitch] made a noticeable difference [in the boat performance].

With the two adults and two children for a total of 415-lbs crew weight, and with six-gallons of fuel aboard, now [using the four-bladed propeller of 10.375-inch diameter by 12-pitch] the boat reaches plane in about four-seconds or about five-seconds, [whereas before changing the propeller the time to reach plane was twice as long, about eight-seconds to ten-seconds].

I would still like more power, but I’m happy enough [with the different performance obtained by changing to the four-bladed propeller] to stop looking for a [higher horsepower] outboard for now.

[jimh]

Reducing the propeller pitch reduces the load on the engine, permitting the engine to be able to accelerate into it rated power band.

When you reduced the propeller pitch to 12-inches from 14-inches, you reduced the load on the engine.

Generally there is no a problem for a three-bladed propeller to have sufficient blade area to be able to convert 40-HP into useful thrust to propel a small boat. Three-bladed propellers work quite well even when used with engines of 250-HP or more. To think that a 40-HP engine needed more than three blades to produce good thrust seems like a bit of a stretch. The reason that most propellers in use are three-bladed is because the three-bladed propeller is generally a very good all-around propeller.

I don't see any mention of engine speeds or boat speed taken when using the new propeller. Time to plane is often related to hull shape, weight distribution, hull trim, and engine trim settings.

[Lakedays]

Top [boat] speed seems almost the same [as with the previous 14=pitch propeller]. The top boat speed may be 1- or 2-MPH faster with the new 12-pitch propeller.

The new propeller has also improved boat acceleration when the boat speed has slowed; the [lack of the ability of the boat to accelerate rapidly when having slowed down] was also bothering me.

I find that the new 13-footer boats from Boston Whaler are set up with a four-bladed propeller with 10.2-inch diameter and 14-pitch to be interesting.

Q4: what caused Boston Whaler to select that propeller?

[jimh]

I find that the new 13-footer boats from Boston Whaler are set up with a four-bladed propeller with 10.2-inch diameter and 14-pitch to be interesting.

Q5: What propeller was being used previously with the 13-foot boats from Boston Whaler prior to 2023?

Q6: what engine was being used previously with the 13-foot boats from Boston Whaler prior to 2023?

[jimh]

Q4: what caused Boston Whaler to select that propeller?

Boston Whaler is actually a division of Brunswick, so they use Mercury engines, and Mercury propellers. They have access to any engine and propeller they want to use on a particular boat. The most reasonable cause for Boston Whaler setting up a boat with a particular engine and propeller combination is their on-water testing showed that combination to be the best for all-around use of the boat.