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mach26 300's
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1,216 Posts
Discussion Starter #1
this weekend one of my 300mercs starting dropping rpms from about the 4k rpm range and would not let me go over that. it acted like it was starving for fuel and started bouncing different rpms all over the place, it would go from 4k to 1500k rapidly. anyone know what to check first?? sound electrical or fuel related??? i brought the boat back to so cal so i can have it worked on or fix it myself. thanks
 

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this weekend one of my 300mercs starting dropping rpms from about the 4k rpm range and would not let me go over that. it acted like it was starving for fuel and started bouncing different rpms all over the place, it would go from 4k to 1500k rapidly. anyone know what to check first?? sound electrical or fuel related??? i brought the boat back to so cal so i can have it worked on or fix it myself. thanks
temp sensor ?
how old is the water pump impeller ?
 

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Registered
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2,234 Posts
Rule #1, compression check first...Allows you to see the plug (lean/rich) and compression tells a lot of stories.

GT :)hand
 

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06 Mach 22 w/2.5 Drags
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200 Posts
what up man? hit up the regatta this year?

i have heard that when the rectifier starts to fail it can make the motor act exactly how you are describing. how far are you from SD? Joe would be a good guy to get with about this issue.

this weekend one of my 300mercs starting dropping rpms from about the 4k rpm range and would not let me go over that. it acted like it was starving for fuel and started bouncing different rpms all over the place, it would go from 4k to 1500k rapidly. anyone know what to check first?? sound electrical or fuel related??? i brought the boat back to so cal so i can have it worked on or fix it myself. thanks
 

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mach26 300's
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1,216 Posts
Discussion Starter #6
whats up, na did not make it down there this year. i'm about two hours from SD, i brought the boat back home and am taking it to my guy up here today so we will see what he says. you make it out this year?

what up man? hit up the regatta this year?

i have heard that when the rectifier starts to fail it can make the motor act exactly how you are describing. how far are you from SD? Joe would be a good guy to get with about this issue.
 

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06 Mach 22 w/2.5 Drags
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200 Posts
whats up, na did not make it down there this year. i'm about two hours from SD, i brought the boat back home and am taking it to my guy up here today so we will see what he says. you make it out this year?
nah, i was out the weekend before and again this weekend.
well i hope that your guy is able to get it sorted out for you quick status. if not, hit me up and ill hook you up with Joe's #. Guy's an impressive outboard tech, he can figure out anything.
 

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Speedy Member
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6,785 Posts
Dustin, Check the water/fuel seperators inside the cowls. The have a sensor in there. You may have some water in the fuel if you get it from the docs at all. That was the first and only problem I encountered with those engines. Pour the fuel into a clear jar and see if there is water and/dirt etc. Im guessing that is the problem.

Let me know.

Tony
 

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mach26 300's
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1,216 Posts
Discussion Starter #9
thanks tony i just took it to the shop and he is going to look at it and do a tune up on both motors, figured i might as well while there down there. i thought the same thing and i should have took the seperators before i brought it down, i hope thats all it is. besides that the boat has been running awesome and have had not problems. hope all is well with you.

dustin


QUOTE=Jetboatguru;696199]Dustin, Check the water/fuel seperators inside the cowls. The have a sensor in there. You may have some water in the fuel if you get it from the docs at all. That was the first and only problem I encountered with those engines. Pour the fuel into a clear jar and see if there is water and/dirt etc. Im guessing that is the problem.

Let me know.

Tony[/QUOTE]
 

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Speedy Member
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6,785 Posts
Everything is great here. Ill bet ya anything that is your problem. I went through big time. The very first place I put gas in had water in their tanks and it would run like shit right at 4k. Sometimes it wouldnt even fire. I always carried spares after that. If they are both doing it then that is a sign right there. Im pretty confident that is the problem.
 

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mach26 300's
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1,216 Posts
Discussion Starter #11
dam tony i hope your right, that sounds like that definitely is what it is and was doing, the other motor was not doing it but or atleast was not yet. we will see, glad all is great man. will let ya know what happens.


Everything is great here. Ill bet ya anything that is your problem. I went through big time. The very first place I put gas in had water in their tanks and it would run like shit right at 4k. Sometimes it wouldnt even fire. I always carried spares after that. If they are both doing it then that is a sign right there. Im pretty confident that is the problem.
 

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mach26 300's
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1,216 Posts
Discussion Starter #12
sounds good appreciate it man, i'm hoping tony(jetboatguru) solved my problems already:D


nah, i was out the weekend before and again this weekend.
well i hope that your guy is able to get it sorted out for you quick status. if not, hit me up and ill hook you up with Joe's #. Guy's an impressive outboard tech, he can figure out anything.
 

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Banne'd
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2,568 Posts
if that were an omc it would be a piece of cake. On the OMC vro's the pulse limmiter would go out. That would be part of the oiling system, bad limmiter no rpm's.

Sounds like you may have a safe mode, lack of oil maybe???
 

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Under yo mommas bed
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1,884 Posts
The stator has 2 sides to it. A low and a high speed. Check the stator.
 

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mach26 300's
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1,216 Posts
Discussion Starter #15
thanks guys, i have it at my mechanic and i'm pretty sure it is just the fuel/water seperator or clogged filters. i am waiting to hear the diagnosis in a couple days, but electrical was definitely the other possiblitity. thanks
 

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29812
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6,873 Posts
Sounds like the same thing that happened to me...
I had a bad coil and yes there are SIX seperate ones...
Check your coils, its a 150 dollar fix
 

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mach26 300's
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1,216 Posts
Discussion Starter #17
just got back from dropping off the alternator to be rebuilt, it was shot, things were bouncing around like crazy in it, stator was no good. also the wire coming from the alternator to battery, the terminal was broken off so the motor was not getting much voltage at all for it to run.. this is atelast what they tell me, so we will see when i get the alternator back and put on. sound right everyone???????????????:D
 
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