proper outboard and propeller mac26X

[ris]

RPM 13 3/4 X 13
2000 8 mph
3000 10 mph
4000 no data
4500 WOT 19.5 mph

RPM 14 X 9
2000 6.5 mph
3000 9.1 mph
4000 15.5 mph
5250 WOT 21.5 mph

Both tests were 2 people, 24 gal fuel and the boat was basically empty

Above are tests I ran a couple of months apart with the two props I have. Boat came with the 13 3/4" X 13 pitch and we later purchased the 14" X 9 pitch. Not an engineer but most here say hull speed is around 6.5 mph. After a lot of internet research and people here if you stay at hull speed all the time you would be ok with the 13 3/4 by 13 prop as you are only a little above idle. It may in fact hurt the motor even at the slow speed. But as the 14x 9 prop reaches the WOT rpms and the speeds it runs at lower rpms is not much different then the 13 x 3/4 prop we will use the 13 3/4 x13 as a spare. That way if we need to run WOT for some reason for an hour or 2 we will not be hurting the motor with the 14 x 9 prop. After all we paid good money for that motor and want it to last a long time with little maintenance. If you click on the name of the person under their avatar to the left of this page, you can choose to view all of their posts by subject, starting with their newest posts. You can learn a lot from the folks here by doing that. I am interested in cruising long distance so I checked out Sumner and Chinook's posts as they have done long trips. Go with your interests. Also check out the forum search and the mods search. I have viewed all the mods at least 3 times in the last year.

[JotaErre]

I have an X with a Yamaha F50 (a 1998, carburated, 4-cylinder unit). I don't know the exact measures of the propeller, but the engine is labelled "High Trust". I can achieve 5.000 rpm. I might even get some more, but I've never tried... I don't want to break the engine.

The highest speed I've achieved were 13 knots with 2 people onboard, ballast tank full and a clean hull.

[dlandersson]

Outboard model?

RPM 13 3/4 X 13
2000 8 mph
3000 10 mph
4000 no data
4500 WOT 19.5 mph

RPM 14 X 9
2000 6.5 mph
3000 9.1 mph
4000 15.5 mph
5250 WOT 21.5 mph

Both tests were 2 people, 24 gal fuel and the boat was basically empty

Above are tests I ran a couple of months apart with the two props I have. Boat came with the 13 3/4" X 13 pitch and we later purchased the 14" X 9 pitch. Not an engineer but most here say hull speed is around 6.5 mph. After a lot of internet research and people here if you stay at hull speed all the time you would be ok with the 13 3/4 by 13 prop as you are only a little above idle. It may in fact hurt the motor even at the slow speed. But as the 14x 9 prop reaches the WOT rpms and the speeds it runs at lower rpms is not much different then the 13 x 3/4 prop we will use the 13 3/4 x13 as a spare. That way if we need to run WOT for some reason for an hour or 2 we will not be hurting the motor with the 14 x 9 prop. After all we paid good money for that motor and want it to last a long time with little maintenance. If you click on the name of the person under their avatar to the left of this page, you can choose to view all of their posts by subject, starting with their newest posts. You can learn a lot from the folks here by doing that. I am interested in cruising long distance so I checked out Sumner and Chinook's posts as they have done long trips. Go with your interests. Also check out the forum search and the mods search. I have viewed all the mods at least 3 times in the last year.

[ris]

The motor is a 2015 Honda 60 with the high thrust. It has the 2.33:1 gear ratio. There is a mathematical problem with the 5250 rpm/21 mph WOT number. Most likely it is the rpm gauge. If we ever stop having windy weekends from these fronts we are going to retest the numbers for the 14 X 9 prop.

[dlandersson]

Roger, so I can't help you. Each model supports different props. A 98 Merc, for example, won't support props more than 12"

The motor is a 2015 Honda 60 with the high thrust. It has the 2.33:1 gear ratio. There is a mathematical problem with the 5250 rpm/21 mph WOT number. Most likely it is the rpm gauge. If we ever stop having windy weekends from these fronts we are going to retest the numbers for the 14 X 9 prop.

[Dandee]

I'm relatively new to the group (and the Mac 26x) although sailing mono's and cats for years, so forgive me if the discussion has already come up, I have searched and not found specific to my engine. My 26x has a Mercury Force 50hp with a severely dinged up prop, what is the best recommendation pitch/size for a replacement for this engine?

[dlandersson]

More information would be helpful.

What is your altitude?

What is your use (towing, going for speed, heavily laden/got several people, etc.)?

Answers are free.

Answers requiring thought - $.50

Correct answers - $1

I'm relatively new to the group (and the Mac 26x) although sailing mono's and cats for years, so forgive me if the discussion has already come up, I have searched and not found specific to my engine. My 26x has a Mercury Force 50hp with a severely dinged up prop, what is the best recommendation pitch/size for a replacement for this engine?

[yukonbob]

Wrong answers - Priceless

[Dandee]

I am in Lake Ontario, so consider sea level. How will I use the boat? well, as background I have for years with a traditional keelboat been tied to a short sailing distance from dock (for a working guy with only weekends or a couple of weeks in the summer for cruising), so I'm looking forward to getting to some new cruising grounds motoring and sailing when there and conditions are great. Also looking forward to loading up on the trailer and taking off somewhere I haven't been able to get to before. There will just be the 2 of us now - kids are gone We also hope to do some canal cruising - the Rideau and Trent canal systems are nearby and one day perhaps the Great Loop!
Roger

[dlandersson]

So, no plans to do a lot of tubing/towing/water skiing, etc?

Think about SS or aluminum - both have pro's.

Note that I have several props - spent my 2nd summer swapping out a lot - playing with them. Changing a prop is not hard.

I have a 1997 X with a 1998 50 HP Merc - non-bigfoot. A 12.5 x 8 or 12.5 x 9 should be your best best. Often a prop designed for a pontoon boat (think cupping) will work well.

https://www.mercurymarine.com/en/us/pro ... #/step-one

Having said that - my best speed - w/o ballast - is 15 knots. I'm happy with that.

More to the point, your best ROI for fuel/speed is probably around 6 - 6.3 knots

I am in Lake Ontario, so consider sea level. How will I use the boat? well, as background I have for years with a traditional keelboat been tied to a short sailing distance from dock (for a working guy with only weekends or a couple of weeks in the summer for cruising), so I'm looking forward to getting to some new cruising grounds motoring and sailing when there and conditions are great. Also looking forward to loading up on the trailer and taking off somewhere I haven't been able to get to before. There will just be the 2 of us now - kids are gone We also hope to do some canal cruising - the Rideau and Trent canal systems are nearby and one day perhaps the Great Loop!
Roger

[dlandersson]

A good prep for a great loop is to visit Chicago - hint, hint.

We also hope to do some canal cruising - the Rideau and Trent canal systems are nearby and one day perhaps the Great Loop!
Roger

[DHK79]

While a lot of these posts have some good info in them, they don't address the OP's problem. If you can't get up to the proper RPM as listed in the engine specs, you have too much prop. If you're constantly red-lining the engine, you have too little prop. Prop selection guides (posted by prop manufactures) can help, but you are unlikely to find a Mac listed on them. In terms of hull performance I've found selecting a 26' pontoon boat (and no I'm not smoking anything funny) with your outboard will get you close.

A slightly bigger diameter will give you a bit more thrust at low speeds for maneuvering, but may shave off a bit at WOT.

As a bench mark, I'm running a Yamaha 70 with a 14x11 and can go 22 mph.

[Tomfoolery]

I am in Lake Ontario, so consider sea level. How will I use the boat? well, as background I have for years with a traditional keelboat been tied to a short sailing distance from dock (for a working guy with only weekends or a couple of weeks in the summer for cruising), so I'm looking forward to getting to some new cruising grounds motoring and sailing when there and conditions are great. Also looking forward to loading up on the trailer and taking off somewhere I haven't been able to get to before. There will just be the 2 of us now - kids are gone We also hope to do some canal cruising - the Rideau and Trent canal systems are nearby and one day perhaps the Great Loop!
Roger

Substitute Erie Canal for Rideau and Trent-Severn Canal, and you've described my history with boats in this area. And I can get to Toronto much faster with the boat on the trailer than I ever could sailing or motor-sailing across the Lake. More time knocking around places I want to visit than the time just to get there, as with a keel boat.

As to your prop, I have no specific advice other than to assess performance with your beat-up prop, and consider more or less diameter and pitch, depending on how it works now. The size should be stamped on the hub, so look closely.

And also consider that some folks intentionally overprop their engines for long trips at slow speeds (like canal cruising), to keep engine speed down for fuel savings and noise reduction. But if you want the best all-around prop, you should aim for engine speed within the rated speed at WOT, with or without ballast, depending on how you use your boat (mine's set up for no ballast, since I like speed every once in a while, and I pull a wakeboard sometimes, too).

[mrron_tx]

I have a 70hp Suzuki four stroke with a Solas SS 3x13 3/4 x 13 on My I have been up to 26+ sog on a slightly choppy lake.... not a race boat at all.... but did have people scratching they're heads as a sailboat goes by that fast Ron. BTW....that's with no ballast moderate load & two people on board.