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08-13-2018, 05:03 PM
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#1
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Ensign
Join Date: Aug 2018
Posts: 6
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Unable to get over 20MPH
Hi everyone,
Want to start by saying new to this forum and second year boating.
I have a 2005 Maxum 2400SC3 5.0L. Boat ran great in June. Was able to plain and get up to 35MPH. Was away for a while in July but he next time I was able to use boat was late July.
Now I am unable to get boat to plane, and max mph is 19. RPM's seem to stall around 3100.
I did start season with a 21 pitch prop, but I changed it last week to a 19. Did notice RPM's go to 3500 and MPH to 22.
I do have marine growth as it is unpainted. Could marine growth cause this type of problem?
Engine has 480 Hours. Boat was very well maintained by previous owner.
Thanks!
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08-13-2018, 08:00 PM
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#2
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Captain
Join Date: Dec 2015
Location: Florida
Posts: 522
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Growth will definitely keep you from planning out..
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08-13-2018, 08:16 PM
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#3
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Ensign
Join Date: Aug 2018
Posts: 6
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Wow, I had no idea. Right at waterline the growth is about 2-2 1/2" long, further down much less.
Is it possible to test engine by seeing if rpm's can reach 4000? I tried but the warning alert buzzer started sounding.
Thanks again.
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08-13-2018, 08:20 PM
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#4
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Admiral
Join Date: Mar 2012
Location: Lake Powell
Posts: 1,613
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Is it a carberated engine? If so it sounds like the secondaries are not opening.
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08-13-2018, 08:23 PM
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#5
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Ensign
Join Date: Aug 2018
Posts: 6
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No, its a MPI 5.0L
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08-13-2018, 09:45 PM
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#6
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Admiral
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 10,626
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I would start with a bottom cleaning. This has a bigger impact than you would think.
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1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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08-13-2018, 10:06 PM
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#7
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Admiral
Join Date: Dec 2010
Location: central Illinois
Posts: 2,294
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If you are going to leave your boat in the water without antifouling paint rent a slip with a boat lift...
Roger
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08-14-2018, 10:20 AM
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#8
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Lt. Commander
Join Date: Oct 2017
Location: Spokane, WA
Posts: 228
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I wonder if your gas is bad/ old after setting. Also depending on where you are boating the water is hotter in July which could effect your water & fuel temps. I can't imagine 30-40 days of marine growth would slow the boat that much. Was your U/W configuration the same each time ie; fuel, water, people, and gear?
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08-14-2018, 02:24 PM
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#9
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Ensign
Join Date: Aug 2018
Posts: 6
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Quote:
Originally Posted by MoonRiver
I wonder if your gas is bad/ old after setting. Also depending on where you are boating the water is hotter in July which could effect your water & fuel temps. I can't imagine 30-40 days of marine growth would slow the boat that much. Was your U/W configuration the same each time ie; fuel, water, people, and gear?
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Last year filled tank and added proper amount of stabilizer.
As for U/W config, pretty much the same.I have been out about three times since, including the last time with prop change.
Should I test the rpm by racing engine in neutral? Or could this damage the engine? I just ant to see if it will reach 4K.
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08-14-2018, 02:28 PM
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#10
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Moderator
Join Date: Apr 2008
Posts: 5,690
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Quote:
Originally Posted by IT-Man
Wow, I had no idea. Right at waterline the growth is about 2-2 1/2" long, further down much less.
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This is too much growth. Haul the boat and clean the bottom. Max RPM should be between 4400-4800.
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08-14-2018, 02:41 PM
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#11
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Admiral
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 10,626
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Reving the engine in neutral proves nothing and can do damage. Without a load even an engine with a missing cylinder will rev easily.
__________________
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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08-14-2018, 03:36 PM
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#12
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Admiral
Join Date: Mar 2012
Location: Lake Powell
Posts: 1,613
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Something is wrong other than the growth. When was the last complete tune up? Plugs, cap, rotor etc...
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08-14-2018, 05:35 PM
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#13
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Lt. Commander
Join Date: Oct 2017
Location: Spokane, WA
Posts: 228
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I would haul it out clean the bottom, replace that old gas and fuel filter, give it a basic tune-up (plugs, wires, rotor, points, and cap) maybe even a new coil while your there and put the 20" prop back on.
Basically try to go back to your 35mph baseline and check your rpms again. Tach's are not always accurate.
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08-14-2018, 09:30 PM
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#14
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Lt. Commander
Join Date: Sep 2017
Location: Vancouver, Canada
Posts: 102
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I had a similar problem earlier this year when I had a couple of extra people on board. I couldn't get up on plane and was stuck at 3100 RPM pushing water.
Based on the advice of the fine gentlepeople on this board, all I had to do was trim the drive all the way down, then trim it back up slightly when up on plane. Worked like a charm. Prior to that, I was getting one of the passengers to go sit right up forward in the cabin, which also worked, but was not at all convenient...
I understand from my reading here that using the trim tabs can also help to get up on plane, though I'm not entirely sure how they should be used.
FYI, I get marine growth very quickly and lose about 200-300 RPM as a result.
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08-15-2018, 03:06 AM
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#15
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Admiral
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 10,626
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I would do one thing at a time otherwise you’ll never know what the real issue was plus you can spend all kinds of money unnecessarily. IMO start with cleaning the bottom.
__________________
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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08-15-2018, 04:52 AM
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#16
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Lt. Commander
Join Date: Oct 2017
Location: Spokane, WA
Posts: 228
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It's a pretty major event for me to haul my 2700scr back and forth from the lake to the house so I tend to do a couple extra things while she's out of the water. But I do agree with Mike "one thing at a time" until you find the cause.
Please follow-up with us so we can all learn from this situation. I'm curious to know if the marine growth was the culprit.
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08-15-2018, 02:01 PM
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#17
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Moderator
Join Date: Apr 2008
Posts: 5,690
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Take it to a boatyard or marina and pay for a short-haul. Call around and get prices. It is very common to arrange a powerwash with the short haul. They usually give a time limit (1-4 hours) or you end up paying by the hour. They can leave it in the slings and powerwash it right there. If you need to do any other minor work, like zincs, or clean intakes, that is a good time. Many places will charge extra for blocking, which isn't necessary for what you're doing. Unless they are hauling a lot of boats that day, you can usually sit in the slings.
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09-08-2018, 08:05 PM
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#18
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Ensign
Join Date: Aug 2018
Posts: 6
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Well I took the boat out, and holy crap. Here are some photos. Started on the cleanup and will be putting on bottom paint. I contacted interlux for primer and paint for my region.
We will see how the spring goes. Thanks to everyone!
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09-08-2018, 10:36 PM
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#19
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member
Join Date: Apr 2018
Posts: 346
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Quote:
Originally Posted by IT-Man
Well I took the boat out, and holy crap. Here are some photos. Started on the cleanup and will be putting on bottom paint. I contacted interlux for primer and paint for my region.
We will see how the spring goes. Thanks to everyone!
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I'm surprise you make 20 M/H with that jungle on your boat....LOL.
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09-09-2018, 02:35 AM
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#20
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Ensign
Join Date: Aug 2018
Posts: 6
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ik right.
Last couple of week could only get 10 mph. lol
Started cleaning process with pressure washer. Got a lot off. Need to get between the bunks and scrape off barnacles.
Ordered set of Brownell Trailer lifts. Should help!
Will keep you all posted on the progress and results....
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