1995 5.7 Fuel Injected Mercruiser "Cuts Out" on hard accel out of the hole.

sleddude

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I have a 1995 Rinker 232 bowrider with 1995 Fuel Injected Merc with Alpha 1. For the most part, this motor has been flawless, but has reoccuring fuel injection issue.

This season, I have run approx 100 gallons of gas through the boat.

Yesterday, I fueled up 30 gallons at a marina on Lake Winnepesaukee in NH. with 8 people on board, we went for a cruise for about 2 hours. We cruised mostly on plane at slow speeds.

After about 2 hours, our trip took us thru a no wake zone and we idled for about 20 minutes total in and out of a marina. When I got back to open water, I went to WOT and the boat started revving up and the bow started lifting up, then it sounded like a puff of air came out of the engine and it lost all power, and the bow dropped back down. I throttled back down and tried again (the motor never cut out completely). I tried again and same thing happened. Then I eased into the trottle and stayed under 1/2 throttle. It took a while, but the boat slowly came up on plane. Once i was on plane, I could throttle up and down as hard as I wanted and no problem. We cruised back to the starting point and I dropped everyone off. I then went back out into the lake with just one other person in the boat. Same results, I could not accellerate out of the hole hard or it would "puff" and lose power, but I could ease into the throttle and get it up on plane. Once on plane, i could go WOT without a problem.

This morning, I filled up at an Automotive gas station (while on trailer), and put in Star Tron Enzyme and Sea Foam in quantities recommended. I put the boat in the lake to run it hoping the additives would help clear up any fuel contamination/separation issues. As I pulled away from the dock, I went to WOT and the same problem occurred, So i eased into it and got it up on plane and proceded to run it for about 1/2 hour on plane. When I backed it down to headway speed and then Throttled up, it worked perfect. I did several "hole shots" and it worked flawlessly, so I assumed the fuel treatments had worked. I then idled for about 3 minutes and tried again, and the problem reoccurred....crap! It seemed if I throttled up immediately after coming down off plane, it worked fine. However, if I let it idle for any period of time then tried, it would not function properly.

I then changed fuel filters. I expected the one I took off to be full of water, however, there was very little, if any. there was some dirt and junk in the filter though. Unfortunately, when I left the marina after changing filters, I had to go through a no wake zone that took about 4 minutes, and when I got to open water and throttled up, the problem was still there. The boat also revs up fine in nuetral, this only happens in gear with a load on.

Its back on the trailer now.

I am virtually positive this is a fuel/fuel injection issue. When I first got the boat 10 years ago, it did the exact same thing when I was extremely low on gas (i learned never to trust my guage when it was below 1/2 tank). Since then I have always kept the tank at least 1/2 full.

The mechanic fixed similar problems in the past, 6 years ago for $400, and 3 years ago for $180. Each time it seemed like he said it was a Fuel Injection "module" or "board". I would like to know what is causing this to avoid it in the future. Also, money is a little tight, and if this is an easy fix, i would like to do it myself if at all possible.

One note, the noise it makes as it cuts out may be a backfire, but it does not make the normal "bang" noise, it is more like the sound of a blast of high pressure air.

let me know what you think
 

Grub54891

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Re: 1995 5.7 Fuel Injected Mercruiser "Cuts Out" on hard accel out of the hole.

Re: 1995 5.7 Fuel Injected Mercruiser "Cuts Out" on hard accel out of the hole.

I'm taking a guess here but are the exhaust flappers intact? They could have wore out and fell down causing a restriction in the bullhorn,causing an exhaust restriction.
 

sleddude

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Re: 1995 5.7 Fuel Injected Mercruiser "Cuts Out" on hard accel out of the hole.

Re: 1995 5.7 Fuel Injected Mercruiser "Cuts Out" on hard accel out of the hole.

I may be showing how green I am here, but the exhaust is through prop, not through hull. Not sure exactly what the flappers are or how to check?

thanks,
Dan
 

Grub54891

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Re: 1995 5.7 Fuel Injected Mercruiser "Cuts Out" on hard accel out of the hole.

Re: 1995 5.7 Fuel Injected Mercruiser "Cuts Out" on hard accel out of the hole.

They are in the exhaust "y" pipe or bullhorn as some call it.Where the risers connect to the downtube.You have to pull the rubber bellow off where it connect's to the y pipe.They are right there on top.The purpose of them is to stop water from coming in when slowing down fast or going quickly in reverse.Even helps when launching or pulling out on a steep ramp.If they are broken they fall down into the y pipe and can get stuck.Sometimes you have to remove the lower unit to get em out if they broke. Let us know if ya get it cured! Grub
 

achris

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Re: 1995 5.7 Fuel Injected Mercruiser "Cuts Out" on hard accel out of the hole.

Re: 1995 5.7 Fuel Injected Mercruiser "Cuts Out" on hard accel out of the hole.

.... Not sure exactly what the flappers are or how to check?

This is what they look like, or should look like...

attachment.php


It's quite likely yours have fallen off, as they are the old style, and prone to breaking... By I seriously doubt that is causing your problem.... When were the spark plugs last changed?

Chris.......
 

sleddude

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Re: 1995 5.7 Fuel Injected Mercruiser "Cuts Out" on hard accel out of the hole.

Re: 1995 5.7 Fuel Injected Mercruiser "Cuts Out" on hard accel out of the hole.

brought to mechanic who did a quick lake test. he looked into the throttle bodies and said that one injectior was not spraying fuel. he is trying the easy fix to clean the injector. Hopes to retest today. If it doesn't work, he said the next step is to replace injectors for big $$$$$ ($900)

I am in a jam because I need it for the weekend to go to an Island on the lake for Vacation. any comments welcome
 

sleddude

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Finally found the problem. It was a combination of low oil and bad oil pressure sensor. When the bow rose up, the oil flowed to the rear, and the sensor did not sense any pressure. The mechanic disconnected the sensor and it rand flawlessly. We did an oil change and put a new sensor in and bingo, problem solved.

I hope this helps someone since this has been dogging me for years.
 

Bondo

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Finally found the problem. It was a combination of low oil and bad oil pressure sensor. When the bow rose up, the oil flowed to the rear, and the sensor did not sense any pressure. The mechanic disconnected the sensor and it rand flawlessly. We did an oil change and put a new sensor in and bingo, problem solved.

I hope this helps someone since this has been dogging me for years.

Ayuh,..... Odd combo, indeed,... Glad ya figured it out,.....
 

Grub54891

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Well,that is a strange combo of the problem. I'd also be looking into why it's using oil,how many hours since it was checked? I myself check my oil every outing,and its full all season. But then I only get 50 hours or so most of the seasons. Even though 200 hours has happened in the past,no low oil.
 

achris

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As with any EFI/MPI engine, a scan tool would have shown the error in a flash. Low oil pressure puts the ECU into 'Guardian' mode, and based on the error will only allow a set amount of power. eg, IAC failure will only allow 90%, and an overheat, depending on the temperature can cut the power all the way down to 10%. Low oil pressure will set the engine into 10% power. When/if oil pressure is restored, full power is also restored, but it does set an error code which will be viewable with a scan tool or the diagnostic software.

Here's what the Merc service manual has to say about the older model, 'power eduction mode'....

EFI Guardian.jpg

That all said, I would have been searching for a fuel problem, until a scan tool was put on and the error code revealed...

Chris......
 
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