User Tag List

Page 1 of 2 1 2 LastLast
Results 1 to 15 of 23
  1. #1
    Join Date
    Apr 2016
    Location
    delray beach florida
    Posts
    13
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    4
    Likes (Received)
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    21 superboat slowed down

    So, I have a 1987 21" Superboat. It has a 12" setback and It is rigged with a 2004 mercury 250 3.0 with 520 hours. The boat used to run 72-74 mph all day at 5,200-5,400rpm. Over the past few months, It has been going slower and slower. It currently only does 63-64mph at 5,000-5,150rpm. I brought it to my mercury mechanic and he went over the entire entire top to bottom. Compression was strong, plenty of spark, and a clean fuel system. I run a trophy 26P propellor and have since i got the boat. About 100 hours ago I replaced the propellor with a brand new propellor, same one. The boat was still running 72-74mph after getting the new propellor.


    If it isn't the engine and it isn't the propellor, what could be wrong with the hull? The boat does not sit crooked/lower in the water, so I do not believe the core is wet, But I have absolutely no clue what else could be slowing me down 10mph.

    Also, Could this mean the engine is due for a rebuild? Even with solid compression numbers? I have ran the boat in between 4,000-4600RPM since I got it with 262 hours on it.

    Im sure many of you guys recognize this boat.
    Any help is appreciated, Located in South Florida

    Click image for larger version. 

Name:	95524f93-dc30-46b2-8b8d-ad777d3.png 
Views:	106 
Size:	1.29 MB 
ID:	469092Click image for larger version. 

Name:	7f2f18af-0e87-4406-93bf-98101f5 1.41.39 PM.jpg 
Views:	87 
Size:	163.0 KB 
ID:	469093

  2. #2
    Join Date
    Jun 2006
    Location
    Silverton section of Toms River, NJ/Stuart, Florida
    Posts
    10,205
    Thanks (Given)
    374
    Thanks (Received)
    314
    Likes (Given)
    821
    Likes (Received)
    1999
    Mentioned
    1 Post(s)
    Tagged
    1 Thread(s)
    What is your WOT? Should be 5750 I believe.

  3. #3
    Join Date
    Apr 2016
    Location
    delray beach florida
    Posts
    13
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    4
    Likes (Received)
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by vnemous View Post
    What is your WOT? Should be 5750 I believe.
    You are right, the engine can spin up to 5,750. It used to spin to 5,400, now it only spins 5,100. I have not changed anything

  4. #4
    Join Date
    Feb 2019
    Location
    Plainview, NY
    Posts
    142
    Thanks (Given)
    1
    Thanks (Received)
    2
    Likes (Given)
    65
    Likes (Received)
    11
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    injectors are clogged probably

  5. #5
    Join Date
    Apr 2016
    Location
    delray beach florida
    Posts
    13
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    4
    Likes (Received)
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jcoop421 View Post
    injectors are clogged probably
    I had the injectors cleaned recently. I just had the entire engine gone over and it was nothing on the engine. Could the engine be tired? even though compression numbers are fine?

  6. #6
    Join Date
    Sep 2012
    Location
    Florida
    Posts
    440
    Thanks (Given)
    2
    Thanks (Received)
    15
    Likes (Given)
    9
    Likes (Received)
    84
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Might be dropping a coil.

  7. #7
    Join Date
    Oct 2001
    Location
    #2 iron from the Mayo clinic, Fla. / Blue Ridge, VA.
    Posts
    8,236
    Thanks (Given)
    373
    Thanks (Received)
    155
    Likes (Given)
    484
    Likes (Received)
    1135
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    is that on gps ?
    most overnite successes usually take at least 10 years


    Certified turd polisher,

  8. #8
    Join Date
    Apr 2001
    Location
    Western Pennsylvania
    Posts
    3,882
    Thanks (Given)
    48
    Thanks (Received)
    92
    Likes (Given)
    184
    Likes (Received)
    378
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Shouldn't loose 10mph with only 200-300rpm decrease. Have a scanner to verify RPM with tach?
    Checkmate 2002 Convincor 270 496 MAG-HO

    2003 Cougar 22MTR w/300xs SOLD
    90 21Skater w/300xs - sold
    98 STV Euroski w/280 - sold


    2006 Trailblazer SS 6.0l 395hp

  9. Thanks KIRCHNER thanked for this post
  10. #9
    Join Date
    Apr 2016
    Location
    delray beach florida
    Posts
    13
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    4
    Likes (Received)
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by mr fun View Post
    is that on gps ?
    Yes, Garmin GPS

  11. #10
    Join Date
    Apr 2016
    Location
    delray beach florida
    Posts
    13
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    4
    Likes (Received)
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I have a Tac and the mercury smartcraft to verify

  12. #11
    Join Date
    Nov 2006
    Location
    Long Island
    Posts
    1,853
    Thanks (Given)
    27
    Thanks (Received)
    36
    Likes (Given)
    219
    Likes (Received)
    227
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    Check to see if the boat is wet
    21 Intimidator 300x Sold
    http://www.youtube.com/watch?v=KBoYUJ58sLE

    1/2 21 Skater 300x Sold
    http://www.youtube.com/watch?v=tKNFL8b6kWo

    30 Activator 850 HP Sold
    https://youtu.be/NZgOTNGKzqg

    30 Concept Twin 300Rs

  13. Likes vnemous, bayman96 liked this post
  14. #12
    Join Date
    Apr 2016
    Location
    delray beach florida
    Posts
    13
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    4
    Likes (Received)
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Trimmed Out15 View Post
    Check to see if the boat is wet
    That was the next thing I was going to do. I dont know what else It could be. I talked to my mechanic today and he said that everything on the engine was good. The only thing I can think of is that the core is wet.

  15. Likes powerabout liked this post
  16. #13
    Join Date
    Nov 2006
    Location
    Long Island
    Posts
    1,853
    Thanks (Given)
    27
    Thanks (Received)
    36
    Likes (Given)
    219
    Likes (Received)
    227
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by suerboatsuperboat View Post
    That was the next thing I was going to do. I dont know what else It could be. I talked to my mechanic today and he said that everything on the engine was good. The only thing I can think of is that the core is wet.
    Tap the bottom with the handle end of a screw driver and you will hear the difference between wet and dry
    21 Intimidator 300x Sold
    http://www.youtube.com/watch?v=KBoYUJ58sLE

    1/2 21 Skater 300x Sold
    http://www.youtube.com/watch?v=tKNFL8b6kWo

    30 Activator 850 HP Sold
    https://youtu.be/NZgOTNGKzqg

    30 Concept Twin 300Rs

  17. Likes suerboatsuperboat liked this post
  18. #14
    Join Date
    Apr 2001
    Location
    Daytona Fl.
    Posts
    10,562
    Thanks (Given)
    5
    Thanks (Received)
    240
    Likes (Given)
    2
    Likes (Received)
    2245
    Mentioned
    7 Post(s)
    Tagged
    2 Thread(s)
    Probably a coil. It won't show up on a scanner. You will lose 10 mph instantly. Either that or you are eating too many donuts?
    " IT'S NOT HOW FAST YOU ARE, IT'S HOW COOL YOU LOOK!!! "

    Check out my new website. liberatorpowerboats.com
    Boat Delivery available













    Things owned. NOTHING!!
    Ain't got no toyz, Ain't got no money! I is jus a poor Florida boy!

    Visit My Liberator Boats Website

  19. #15
    Join Date
    Jul 2001
    Location
    NYC
    Posts
    689
    Thanks (Given)
    0
    Thanks (Received)
    10
    Likes (Given)
    0
    Likes (Received)
    75
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by suerboatsuperboat View Post
    So, I have a 1987 21" Superboat. It has a 12" setback and It is rigged with a 2004 mercury 250 3.0 with 520 hours. The boat used to run 72-74 mph all day at 5,200-5,400rpm. Over the past few months, It has been going slower and slower. It currently only does 63-64mph at 5,000-5,150rpm. I brought it to my mercury mechanic and he went over the entire entire top to bottom. Compression was strong, plenty of spark, and a clean fuel system. I run a trophy 26P propellor and have since i got the boat. About 100 hours ago I replaced the propellor with a brand new propellor, same one. The boat was still running 72-74mph after getting the new propellor.


    If it isn't the engine and it isn't the propellor, what could be wrong with the hull? The boat does not sit crooked/lower in the water, so I do not believe the core is wet, But I have absolutely no clue what else could be slowing me down 10mph.



    Also, Could this mean the engine is due for a rebuild? Even with solid compression numbers? I have ran the boat in between 4,000-4600RPM since I got it with 262 hours on it.

    Im sure many of you guys recognize this boat.
    Any help is appreciated, Located in South Florida

    Click image for larger version. 

Name:	95524f93-dc30-46b2-8b8d-ad777d3.png 
Views:	106 
Size:	1.29 MB 
ID:	469092Click image for larger version. 

Name:	7f2f18af-0e87-4406-93bf-98101f5 1.41.39 PM.jpg 
Views:	87 
Size:	163.0 KB 
ID:	469093

    do you have to trim out more than usual to get to the current rpms? That is always the sign on my 30 that I dropped a coil , I lose 5-8 miles easily with just one coil Down - hope it’s something simple

    1982 12' Eli with 7.5 Evinrude (sold)
    1963 16' Glasspar with 40 hp Evinrude (sold)
    1969 13' Boston Whaler with 40 hp Evinrude (sold)
    1990 20' Searay with Merc i/o (sold)
    1990 22' Activator with 2.5 EFI (sold)
    1998 24' Superboat Step Hull with 300 Pro Max (sold)
    1983 21’ Shadow with 300 promax
    2003 13’ Boston Whaler with 40 hp Merc
    1976 16' Superboat with 75 Yamaha
    2010 30' Superboat Center Console with twin 300 Mercs

    One good hour on the water will make you forget 24 bad hours on land

  20. Likes suerboatsuperboat, bayman96 liked this post
Page 1 of 2 1 2 LastLast

Similar Threads

  1. after market tilt slowed top speed?
    By 40mphjon in forum Technical Discussion
    Replies: 12
    Last Post: 03-26-2015, 07:00 AM
  2. Pitts 21' Superboat vs Hosers 21' Superboat
    By Dirk Pitt in forum General Boating Discussion
    Replies: 40
    Last Post: 06-12-2011, 09:19 AM
  3. Live superboat race at 1pm on superboat.com turbines and all
    By 200VEGAS in forum General Boating Discussion
    Replies: 0
    Last Post: 05-22-2011, 11:59 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •