Mercruiser 3.0L throttle issue "dead spot" when throttling up

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dbusch22

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so my 2002 bayliner 1950 has some strange thing that it does while accelerating.

Let me say first-off that I do love this boat, the boat for the money was great, the boat has never left me stranded, the power and speed are more than adequate for what I do with the boat, which is fishing lake michigan mostly.

I bought the boat used 3 seasons ago, and it has done this ever since i bought it. It has not been a huge issue so i have not pursued fixing it yet.

*** when you leave the dock, even if you have let the engine warm for 10 minutes or so, you get out and start throttling it up, there is an area of the throttle, where the boat just falls flat. If you KEEP the throttle there, the engine will probably end up dying. if you come back down off throttle it will idle fine again, and if you just push past the "dead spot" it will throttle up and you can get out on plane no problem. If i had to guess, i would say this happens about 13 mph or maybe.... 2500 rpms coming off an idle speed. - to settle this for anyone who thinks i have the wrong prop, it is the 21pitch prop that i believe is the recommended size for my boat, i have never changed it.

It pretty much always does this unless you have been running the engine for quite a while. I notice that at the end of my fishing trips, after the motor has been running for hours on idle, that it throttles up just fine.

I have tried seafoam, and carb cleaners, I change the plugs and oil every spring, i run ONLY 93 octane in this boat (which by the way if i run anything less than 93, it seems to sometimes 'deisel' or 'run-on' when i shut the engine off) I don't know what else to do.

any ideas
 

pvmtsux

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

Carb may need to be adjusted, maybe your running a bit rich and it's choking out. When was the last time you replaced your fuel filter?
 

Bondo

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

Ayuh,... It sounds like a Carb problem,...

Try rebuilding it...
 

dbusch22

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

my 3rd season with the boat, (as soon as the ice is out) I have not changed the fuel filter ever... probably should do that? don't know how often it is supposed to be changed or if/or when the previous owner did it.
 

Bondo

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

probably should do that? don't know how often it is supposed to be changed

Ayuh,... Annually, or whenever symptoms are present...
 

JimS123

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

Thats a classic accelerator pump issue. Years back Merc issued a service bulletin and replaced some of the 3.0 liter the pumps with an upgraded model.
 

pvmtsux

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

Ayuh,... Annually, or whenever symptoms are present...

Def. replace that fuel filter. Even if it's not the cause of your problem you should be replacing it each year when you do your annual maintenance.
 

HT32BSX115

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

I bought the boat used 3 seasons ago, and it has done this ever since i bought it. It has not been a huge issue so i have not pursued fixing it yet.
Howdy,


Absolutely replace the filter and rebuild the carb. That will probably solve your immediate issue.


Also, If you have had the boat 3 years and you haven't replaced the raw water pump, changed the drive oil and/or removed the drive and checked the alignment, you are running on borrowed time and you're asking to be stranded out in the lake.


Get yourself an OEM service manual if you plan to do any of this stuff yourself.


Regards,


Rick
 

dbusch22

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

this is only my second boat. I am actually more of a car guy. I built a car for drag racing locally at the strip where I live. Everything I learned was pretty much from trail and error, talking with people, and time spent researching online. I am very mechanically inclined. I can pick up on pretty much any of this, however I don't know of a lot of 'boat' people, so this is all coming over a period of time. I'm sure you all think.. ya what a dumb new guy.. and you may be right, but hey we all have to learn in our own way. Hopefully I don't learn boats the expensive way, as I am not made of money. :) I actually don't know what the 'raw water filter' is. It sounds like a filter that cleans lake water that enters from the lower unit. makes sense. I can google where to find it and change it, maybe find a part # or something. My boat was used and did not come with service manuals. I also have not checked any alignment. I'm assuming that perhaps the alignment can become off from years of torque on the water. Anyhow, sounds like this year, I should get the boat to a professional to do some maint. that I don't have tools for. I will try the fuel filter and raw water filter myself. I am also interested in learning more about the accelerator pump, where it is located, what it does, and how to check/replace it. - I would like to know where I can find that service bulletin. (I am on partial lay-off status at work right now, thanks to the great economy, so I have a bunch of extra time to fiddle online with this stuff)

BTW... every year I change the drive oil, in the fall, every spring i change the engine oil and filter. I fog it every fall and install new plugs in the spring. I put the drive down and also pull the manifold plugs out to drain the water in the fall. I then pour some of the environmentally safe antifreeze in the tubes that attach to the manifold. - I am sure I am probably not doing this the way a shop would do it but I am trying

thanks for all the help thus far!
 

JWebber

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

My 3.0 did this, I also have a bayliner. I had to adjust the accelerator pump linkage to the max postion. these engines run lean from the factory to meet emissions. My dealer told me to do this process and it worked. You will have to download a 3.0 manual and look up the accelerator pump arm linkage positions.
 

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Bondo

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

I actually don't know what the 'raw water filter' is.

Ayuh,... Donno where ya saw that,....

You should add a Water seperating fuel filter, 'cause your's probably don't have 1, 'n every boat Should....
And,..
Rick was talkin' 'bout the Raw Water Pump,...
Which is at the top of the Lower unit...
It's Impeller should be change every year or two....
This manual should pretty much cover your Motor,...
'n This 1 will cover yer Drive...
 

HT32BSX115

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

I actually don't know what the 'raw water filter' is.
There actually ARE raw water filters. I didn't say Raw water filter though..... I said RAW WATER PUMP.

I also have not checked any alignment. I'm assuming that perhaps the alignment can become off from years of torque on the water
Mercruiser actually suggests checking the alignment every year. It can become a REAL problem in older boats that might have a little ROT in the transom or stringers. Mis-alignment can cause coupler failure. It WILL strand you......... and you have to remove/replace the engine and drive to replace it.

I built a car for drag racing locally at the strip where I live. ................. I am also interested in learning more about the accelerator pump, where it is located, what it does, and how to check/replace it.................
Hmm.....and you don't know what an accelerator pump is?:confused:


Well ok. We all had to learn about all this stuff somehow........Yahoo Search is your friend!


BTW... every year I change the drive oil, in the fall, every spring i change the engine oil and filter.
You should change the engine oil in the fall also. It's better to check & change the engine oil in the FALL so you don't leave possibly contaminated oil in the engine all winter. (Mercruiser also suggests it for the same reason)



Cheers,



Rick
 

bnicov

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

The Accelerator Pump is in the carburetor. It squirts more fuel down the venturi to richen the mixture under acceleration. If it is not working like it should, your carb will 'bog' or hesitate under acceleration. Since it's an '02 boat, you probably should remove the carburetor and rebuild it properly yourself if you think you are up to the task or send it out to be rebuilt. A full tuneup wouldn't be a bad idea either, plugs, wires, distributor cap and rotor. As mentioned before, you should be changing your fuel filter as well as the raw water pump impellor every year or at least every other year depending on how much you use the boat. Take it to a marina or qualified boat mechanic to align the outdrive for you. Since you change your outdrive oil and engine oil and filter each year you should be good to go for some worry free boating. Owning a boat doesn't need to be really expensive, if you are handy you should be able to take care of many of the problems that come up. You already know drag racing isn't cheap (it's a good day when nothing breaks).
 

dbusch22

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

Bond-o - both of those RAR manuals, are password protected. Do you have the password?
 

Bondo

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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

Bond-o - both of those RAR manuals, are password protected. Do you have the password?

Ayuh,.... <iboatsforum>...
 

sprobst

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Aug 13, 2010
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Re: Mercruiser 3.0L throttle issue "dead spot" when throttling up

I'm no expert by any means. But, I have a 3.0L (1998 vintage) where I have the very same issue. I mostly live with it. I'm pretty sure it's a carb issue and I plan to rebuild it this year. All of the easy stuff (fuel filter, plugs, wires) are probably good to do but may not help.

On the dieseling issue.......

The 3.0L is prone to dieseling. If you've been running hard (full throttle) and stop, be sure to let it idle for a while before shutting it off. That is a common problem if you don't.
 
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