Announcement

Collapse
No announcement yet.

Top speed for 21B

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Top speed for 21B

    I own a 1987 Mako 21B with an aluminum T-top and trim tabs. I am looking at re-powering with a 150HP. Does anyone have a similar rig and can you tell me what the top speed is and how you like the overall performance?

    Thanks

  • #2
    Absolutely not enough power. My Dad owned a 21B for ten years, and I owned a 21 for a few years. 200 HP is barely enough, and 225 is ideal. With a 225, top speed is between 42-44mph. The Mako 21 is a beefy, heavy boat.
    1987 Mako 254, 2013 Evinrude ETEC 175\'s (sold to my buddy)[br]1988 Mako 20, 2008 Yamaha 200HPDI (sold)[br]1984 Mako 17, 2005 Suzuki 115 (sold)[br]1981 Mako 21 (sold)[br]1978 Mako 17 (sold)[br]1986 Mako 260 (sold)[br]1997 Mako 232 (sold)[br]Tampa, Florida

    Comment


    • #3
      Hes right, don't even consider anything less than 200 hp. I have a 1985 Mako 21B. I bought it with a Yamaha 200. I put a T-top on the boat and the top speed with the boat empty was about 41mph. When I'd load her down with 3 adults and fishing gear, top out was closer to 36-37 mph and just draining gas at about 25+ gph. I very often struggled to get on plane turning a 15" Pitch wheel! With that prop I could only get to about 5300 rpm at WOT. The motor just didn't have enough power to turn ANY prop on that hull. I never had enough power to fight heavy seas or in one case to get myself adequately out of harms way when a panomax class tanker was breathing down my neck in the Miss River! The tanker was going the same speed as I was!

      I repowered with a Merc 225 EFI. Its night and day difference. I turn a Rapture 14.25"x17p prop now. WOT is about 48-49 mph with a light load turning about 5700 rpm. Loading her down doesn't make much difference though. The 3.0 L block is up for the work load.

      Spend a few bucks more and power the boat properly. I can't imagine how dreadful a 150 hp would be on that boat... The 200 was bad enough.

      I can answer almost any question you may have about the hull. I hope this helps.
      Slidell, LA 1993 Mako 261B - Temperance

      Comment


      • #4
        Agree totally. A 150 won't get it.

        I have a 88 21B w/ Johnsion 225. With one person, 1/2 tank and light load......14 1/2 x 21 OMC SST, all trimed up, I get 6000 RPM and 51 MPH on GPS. With a fishing load and 2 folks I cruise at 4400, 32 MPH @ 13.7 GPH.

        Comment


        • #5
          Ring. A huge difference in props there. Your 14.25"x17p Merc prop vs Alcedo's 14.5"x21p OMC. I wonder if that's a difference in the design of the Merc vs OMC props or a motor spec recommendation. You ever tried anything like a 19p+? Just curious as to the difference at WOT and out of the hole.
          Artie Sutherland[br]Rude Attitude -\'76 Mako 25 CC. - SOLD[br]1976 Mako 21[br]2002 Yellowfin 31 - 300 hp Suzukis[br]Gulf Coast, Mississippi[br]

          Comment


          • #6
            Could be a difference in the gear ratio in the lower unit. The Merc is 1.75:1 not sure what the OMC is. The rapture is a very heavy cup and rake prop. Its more silimilar to a 18 or 19 pitch prop. I ran a Merc mirage Plus 15.25" x 19P on the motor... The speed was there, but the hole shot and RPMs weren't there. The Mirage Plus is also a very heavy cup/rake prop and not to mention bigger diameter. I'd like to try a Stiletto 14.25" x 19P when I get the boat back in the water.
            Slidell, LA 1993 Mako 261B - Temperance

            Comment


            • #7
              I took mine out last week when we had a calm day in the sound. I really hadn't gotten to put it to the test on a calm day since repowering in December. @5500RPM's, 65gallons of gas, I did 39kts(45mph). This sounds like it's faster than most of the other guy's with 200's. I do not have trim tabs right now but I am using a sting-ray hydrofoil.
              1980 Mako21 [br] [br]Long Beach MS <\')))>([br]\"I can always find somebody to tow me back in, but I can never find anybody who will tow me out.........\"

              Comment


              • #8
                piece of advice... propping a smaller outboard boat is tough-here's why normally every inch in pitch gives approx 150 rpm but there is the "air out"factor by that i mean -example you're swinging a 15x19 prop max rpm 4800 dead out of the hole-way over wheeled!! you know that engine max rpm is 5500 so you guess that you need to dropapprox 4"pitch so you try a 15x15 now you're turning 6000rpm and you're scared you're gonna blow it up.so what went wrong i used the formula?? it's the air out factor!! after the hull comes up on top rpm will build,some time it takes only 1 or 2 inches.if your rig is a dog out of the hole it's over wheeled-most common thing i run into.listen guys A BIGGER PROP WILL NOT MAKE YOUR BOAT FASTER IT WILL SLOW IT DOWN AND IT WILL EFFECT THE DURABILLITY OF THAT ENGINE IT WILL ALSO CAUSE EXCESSIVE FUEL CONSUMPTION AND CAN CAUSE A DETONATION CONDITION INSIDE THAT ENGINE.DO NOT OPERATE ABOAT WITH AN ENGINE THAT WILL NOT REACH FULL RPM.it doesn't mean any thing that you never go that speed the engine is still over loaded.speed doesn't mean that much what does is engine rpm the engine must reach that spec the manufacture has given to it-it's there for a reason. ring leader that wheel you're trying to swing is way too big you should be glad you didn't detonate that engine.most if not all outboard props are cupped you want a prop that's cupped it will hold the water better.again don't focus on speed-one thing i have learned being in buisness is that everyone lies about the speed of their boat-that's why i bring my hand held gps{lie detecter} it tells all.speed will come with rpms concentrate on getting the correct rpm and the speed will follow and you will notice that the fuel guage isn't working like a fan any more!!!!!

                Comment


                • #9
                  My boat turned 5500 at wide open the other day. I would call the load I had on the boat average since the gas tank tank wont always be that full but I had no ice in the boxes. Is that high enough for max RPM's? I've always heard that anywhere between 5500 and 6000 was a good target. I don't know anybody here so I have no reason to lie about the speed of my set-up, but I can assure you I will gladly lose speed in exchange for gas mileage. if my trip the other day is any indication then it's gonna be terrible.
                  1980 Mako21 [br] [br]Long Beach MS <\')))>([br]\"I can always find somebody to tow me back in, but I can never find anybody who will tow me out.........\"

                  Comment


                  • #10
                    quote:


                    one thing i have learned being in buisness is that everyone lies about the speed of their boat-that's why i bring my hand held gps{lie detecter} it tells all.



                    []Must be a Jersay thing.id="size2">

                    Bring your GPS.[] When I tell you my little Swamp Witch turn's

                    5090-5100rpm is 28.5MPH om GPS you can take it to the bank.

                    The motor is a '92 25hp Rude. It's spinning a 3X12X13 with a bunch of cup added.

                    Comment


                    • #11
                      check your engine's specs and compare this against what it states-forget about what you heard look it up and make sure that way you will know!! now here's the curve... you need to reach that rpm in the conditions in which you normally operate the boat-full load fuel 3 guys cooler full of heinikens{love 'em} and another cooler full of ice.and remember it will run better in the spring and fall-air is denser.so if you're running a little on the high side-more rpm than is called for than leave it alone the engine is now what is considered light!! this is how to prop a boat the right way!!!

                      Comment


                      • #12
                        quote:


                        Originally posted by warthog5


                        [quote]one thing i have learned being in buisness is that everyone lies about the speed of their boat-that's why i bring my hand held gps{lie detecter} it tells all.



                        YEP us boaters are known for streaching the truth about the speed of our boats and the size of our Johnson's[:x)]......(outboards that is)

                        hehe.

                        ]
                        [br]1994 Mako 215 Dual console Optimax 225[br]1978 Mako 19 with 90hp johnson[br]1996 Mako 22[br]1982 Mako 171 Angler 135 Black Max Mercury[br]1987 21b 225 Yamaha[br]1974 23 inboard Gusto gone.[br]1979m21 225johnson \"blue dolphin\" bought off this board and restored [br]with everyone\'s help!!Gone but not Forgotten....[br]1979 20 Mako 115 Suzuki gone[br]1977 19 Mako 115 Johnson gone[br]1976 23 Mako twin 140 Johnsons gone[br]1983 224 with closed transom and bracket[br]And 162 SOB (some other boats)[br]Venice Florida, Traverse city Mi.

                        Comment


                        • #13
                          easy on the jersey thing boys i'm a little sensitive!!

                          Comment


                          • #14
                            Sensitive?[88][88] - In that Jersey kind of way!
                            [br]***[br]\'82 Ski Nautique - Lake Martin, AL[br]\'80 236IB - Lake Martin, AL[br]\'03 Pursuit 2670 - Destin, FL

                            Comment


                            • #15
                              5700 rpm with a normal load is just about right for the Merc 225 EFI. It calls for 5800 max... With the Mirage plus I was only getting 5200 rpm... thats why it was taken off theboat that day and swapped with the Rapture.

                              Thing about my motor is that it never really changes much wether you load the boat or have a few cups of gas inthe tank and a skinny guy named Sammy on board driving her. She runs 5700 rpm. Thats pretty close. It doesn't matter right now... the motor hasn't been started since Dec. 2002... which is bad in another way.
                              Slidell, LA 1993 Mako 261B - Temperance

                              Comment

                              Working...
                              X