Sseveral issues all at once!

rickasbury

Senior Chief Petty Officer
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Jul 13, 2011
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790
Isn't that the way? Boating not for the faint of heart unless you are rich- I'm not.
2006 350 mpi/bravo III. Around 350 hours, 270 Rinker.
It does not get run as it should, but has been running nice- and everything else- but then it does not.
Replaced plugs,cap and router probably 30 hours ago. It had a miss. I had a bad fuel problem and had to pump out 75 gallons of fuel and dispose. Replaced all the filters- and the high pressure fuel pump (one by the filter starboard ) . I've replaced the raw water impeller a couple times- that's about all the issues I've had.
Checked all the fluid levels, verified the outdrive cycles properly, trim tabs fully extend. Usually it takes maybe 7 seconds for it to plane out and runs nicely around 30- its a heavy boat.
Starts right up, idles smoothly and comes up to temp- head out, accelerate and it will not get on plane at 3500 rpm, usually it's running nice at that rpm. Wide open and no reaction beyond that. Like there is to much weight in the back. Opened the hatch, all looks good. The water tank and holding tanks (25 gallon) near full but that has not been a problem, no large mermaids on the rear.

Another odd thing I have a cold water tap up at the helm- the water has become suddenly hot. I have a small hot water heater below and the pump. I have replaced the pump a couple of times and did so recently and only noticed after a couple short trips out. Those are pretty much plug and play. I noticed after I turned the pump off, I turned on the facuet to let the pressure off it seemed to have super pressure and ran for longer than normal. I know the engine sends hot water through the heater, if something rots out inside could that mingle into the fresh water and pressurize the system? We are fresh water and it looks ok.

Also seems like my alternator bearing or internally making noise or all of the above. Also noticed the tone alters when I raised the hatOK. It seems to make a strong hum but hard to isolate to the alternator. I have a raw and fresh water pump....

and lastly, I only checked the bilge once because of the suspected alternator noise. I saw no real amount of water...and that was after it again would not get on plane- we fished a while and did not go far. Tried to run it again on the short trip back, it did start to plane but started falling off so I pulled the throttle back. When I go to storage as it is trailered, there was a ton of water in the boat when I pulled the plug.

I'm heading to the ramp so I can spend a little one on one. It has a/c, a generator, a head with a pump- so 1000 holes in the bottom when you start to add them up.
I'll be checking this thread on the water and update if I can.
Thanks!
.
 

alldodge

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Does the motor have closed cooling?
Is it getting hot?

accelerate and it will not get on plane at 3500 rpm, usually it's running nice at that rpm. Wide open and no reaction beyond that. Like there is to much weight in the back.
Explain what happens going to WOT, does rpm increase but no more speed or no rpm increase?

Water is hot and takes a good while to bleed off pressure with pump off
Might be the hot water tank leak

short trip back, it did start to plane but started falling off so I pulled the throttle back. When I go to storage as it is trailered, there was a ton of water in the boat when I pulled the plug.
Something spring a leak
 

rickasbury

Senior Chief Petty Officer
Joined
Jul 13, 2011
Messages
790
@alldodge thanks for the reply- so when I push the mercuiser down it does zip- no rpm's- like you did not do anything.
So I got the boat out by myself for a couple of hours- same program except when I put the throttle down, it went like normal. Ran across the lake waiting for it- never happened. Went up the river a bit just to let it run- then the waiting was over. Bogged down to the 3500 or so....took it down to idle a couple of times..so spent the time I had left limping home. I have closed cooling, never showed anything abnormal...charging ok as well. No water really this time to drain..the cold water tab went hot about the same time...I was just letting it run. As far as the noise/suspected alternator- the rattle noise could be coming from anywhere...it is making a hell of a hum noise- when i operate the hatch lift it changes the tone- it is orgional to the boat. Im thinking about getting the mocike vessel view to see if i can get some codes- it just runs perfect! Not a miss- zip
Update- I googled this, a post from I boats was the first on the list and replied to by you! It was a neutral safety switch but his control box had a plug on it- my set up does not, could this be my issue and have that switch on the motor, 350 mpi?
 
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alldodge

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Lets start off with a motor serial number
Replaced all the filters- and the high pressure fuel pump (one by the filter starboard )
The pump replaced, was it a single pump above the fuel filter?

With it taking time to start the issues under less load we need to look further into fuel supply. Weak fuel pump, gas tank drawing a vacuum, fuel rail or regulator dirty.

You removed 75 gal of bad gas which could clog up a bunch of things. If the pump you replaced was a boost pump then your HP fuel pump (port side under motor mount) might be of concern

What is the fuel pressure at the rail?
Put a gauge on the rail and run it so when problem starts you can see what the pressure is

Update- I googled this, a post from I boats was the first on the list and replied to by you! It was a neutral safety switch but his control box had a plug on it- my set up does not, could this be my issue and have that switch on the motor, 350 mpi?
Mobile vessel view can help if there are codes, Rinda diacom or Techmate is better but cost more
 

tpenfield

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The description of the running and the problem is a bit difficult to follow . . . but . . . It sounds like after some time of running with normal performance, your engine limits itself to 3500 RPM. Is that correct?

Since it is an MPI engine, it will be difficult to diagnose without having the computer diagnostic program. You may have some codes, but also you may have a situation that is putting the engine into guardian mode (of some sort). It is best to have the diagnostics running when the problem arises.
 

rickasbury

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Jul 13, 2011
Messages
790
I will see if I can rig up a fuel pressure gauge- I assume the fuel pressure is a constant and what goes through the fuel rail is regulated? The pump I replaced is connected to a line going into the fuel filter so I guess that is the boost pump and not the high pressure pump- it just stops accelerating like there just is no more throttle left. It runs and starts fine otherwise, temp is normal. Engine serial number is Ow038097.
Thanks all for the input.. I guess I should look at Mobil vesskview as a minimum..
 

alldodge

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THIS is the parts listing for your motor

Yes the one on the filter is the boost pump
The fuel pump can output pressure up to 60 psi. Your motor injector pressure is set at 43 psi on the rail. Any pressure above 43 psi is returned back to the fuel filter. The regulator (item 13) is mounted on the fuel cooler under the motor mount

THIS is the fuel rail and the schrader valve (item 18) is where pressure is measured, item 14 is the damper. Can rent a fuel pressure gauge from the auto parts store
 

tpenfield

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Rinda Diacom might be the thing to consider for the computer diagnostics. I'm not sure how much detail you will get from Merc's VesselView.
 
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