CONTINUOUSWAVE

Hello. I bought a 1990 Montauk 17 with a 2019 Mercury 90 EFI with the standard gear case (2.07:1). The motor is mounted one hole up. WOT range is 5000-6000.

The previous owner was an older gentleman who didnt really care to go fast, though he had repowered with the current outboard. He sold me the boat with two propellers.

• Black Max three-blade 13-inch x 19 pitch, and I believe this is what the boat was re-powered with. It wasn’t on the boat when I purchased the boat. The seller said he had hit something with it and had it repaired, but he was just using the spare he had bought instead.
• Turning Point Hustler four-blade 13.25-inch x 17 pitch, which came on the engine.
• I have since borrowed and tried a third propeller which is a Black Max three-blade 13.75-inch x 15 pitch.

Performance of the three propellers has been has follows, and none I believe are the “right” prop for the boat:

Turning Point 17 pitch: 38-MPH at 5400 RPM with two people, 10 gallons of fuel. Fully trimmed out -

Black Max 15 pitch: 38 MPH at 6000 RPM with two people, 10 gallons of fuel. Hit RPM limiter well before WOT

Black Max 19 pitch: 41 MPH at 5250 RPM with one person and 8 gallons of fuel. Boat handling was very weird with this propeller, best I can describe it is squirrelly and unsettled. I couldn’t trim up very much without the propeller blowing out and the engine speed immediately jumped but boat speed didn’t. I trimmed down and engine speed dropped and boat speed increased.

Before I go propeller hunting I figured best to poll the general knowledge of this forum. I can take information gathered here to a local propeller shop to try to work out what is best.

I am thinking of either going for a Black Max three-blade 16 or 17 pitch or a Spitfire four-blade 15 or 17 pitch (and likely the aluminum one, not sure I am ready to fork over for a steel propeller, though there is a 17 pitch used one near me for $450).

I actually bought two used props: a 17 pitch Black Max and also the 15 pitch Black Max since they were a good deal. The 17 pitch broke a blade tip when i went to install it, and come to find out it had been repaired.

My performance goals:

- Get the WOT engine speed to be between 5800-6000 when lightly loaded.
- Max speed is less important, I don’t feel like I need to go much more than 40-MPH based off my use to date.
- Accelleration is more important. I will be pulling kids on a tube. I’ll probably hold on to the Black Max 15 pitch for those times since it spun up well.

Thanks for your help

Based on your test data, the BLACK MAX 17-pitch should put the engine speed at full throttle where you want it.

jimh wrote:Based on your test data, the BLACK MAX 17-pitch should put the engine speed at full throttle where you want it.

That’s what I am hoping.

Q1:would you say that the 17-pitch aluminum propeller is the propeller of choice?

ASIDE:

Jim--I have read a lot of your feedback on other prop inquiries and it seems you favor the three-bladed propellers on most of the smaller Boston Whaler boat applications.

Q2: any current thoughts on the SPITFIRE propeller, if top speed isn't my priority?

Mercury seems to have designed the SPITFIRE explicitly for the new crop of four-stroke-power-cycle engines that have less torque in their low-RPM engine speed range.

Shin09 wrote:Q1:would you say that the 17-pitch aluminum propeller is the propeller of choice?

No. If you want the best performance you need to get a steel propeller.

Shin09 wrote:Q2: any current thoughts on the SPITFIRE propeller, if top speed isn't my priority?

I am not familiar with the SPITFIRE propeller. I don't recall any prior mention of that model propeller being used with a MONTAUK 17. If the SPITFIRE propeller is a stainless steel propellor, it would probably give better performance than the aluminum BLACK MAX.

In addition to better performance, a steel propeller will be more durable. A steel propeller will survive a blade strike with soft material in the water much better than an aluminum propeller.

Confusingly Mercury makes both an aluminum and stainless steel SPITFIRE propellers. Both are four-blade, but they are not geometrically interchangeable. Plus the stainless has the [PVS] venting system. Even more confusing is the Quicksilver versions are called Nemesis and Q4, respectively. But the Q4 is only the 4.25-inch-diameter gear case version. The larger gearcase Q4 is a different four-blade steel propeller.

I am curious about the performance I saw with the 19-pitch BlackMax. I had significant port side lean which I attributed to the anode fin and propeller rotation. Is that typically a result of too much stern lift?

The general unsettled-ness was something else though.

Shin09 wrote:I am curious about the performance I saw with the 19-pitch BlackMax. I had significant port side lean which I attributed to the anode fin and propeller rotation. Is that typically a result of too much stern lift?

A list to Port is probably from propeller torque. See the owner's manual for your boat and for your engine about adjustment of the trim tab on the engine located below the anti-ventilation plate that can reduce propeller torque.

If you do not have your own printed copy of the owner's manual, you can use the version of the owner's manual I created in HTML. See

Owner's Manual 9 to 17-foot
https://continuouswave.com/whaler/reference/manual9-17/

and read the section in OPERATIONS about TRIM TAB ADJUSTMENT

https://continuouswave.com/whaler/refer ... ml#trimTab

Note that the engine TRIM position will also affect this tendency to lean. If the engine is not trimmed out properly, the tendency for engine torque to cause a list to Port will be enhanced.

Also, you need to be aware that there will be a general tendency of the hull to lean into the direction the wind is coming from. If you are on plane with a strong wind coming from the Port side, the boat will tend to lean to port because you are probably steering slightly to port to correct for the pressure on the hull from the wind. On a small boat like a 17-footer, you can easily correct for any tendency to lean to port or starboard by shifting crew position on the boat. Or you can shift the position of some moderately heavy object on the boat, like a cooler. I do this all the time on my 24-footer: I either shift my own position or I ask the crew to shift position slightly to even out the athwartship trim. The influence of crew position will be even more noticeable on a 17-footer.