Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

[jrivera]

Hello All......

I have a 1999 Mercruiser 5.7L EFI Shortblock 350 and here is my problem....

The boat starts up right away with no problems and it idles great! From idle thru full throttle the engine is bogging down and will not go over 2k RPM's while its in the water..... The crazy thing is, while its out of the water with the water muffs hooked up, it revs up to 6k RPM's with no problem whatsoever..... I have replaced the fuel pump, fuel pressure regulator and fuel cooler and fuel filter. I have also replaced the spark plugs and coil. I also had the compression checked out and all cylinders are right around 160 which I was told was excellent..... The boat was sitting for 3 years when I purchased it..... I also replaced the Manifolds and Risers as well as the starter and alternator.... What am I doing wrong?!?.....I really think it has to do with the fuel system!!! I have not checked the timing.... Could the timing cause the engine to bog after 2k RPM's??? I also checked the throttle cable and it looks good!!! PLEASE HELP!!! THANK YOU!!!!

 

[Bondo]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

1999 Mercruiser 5.7L EFI Shortblock 350

Ayuh,... Is the fuel Tank given it up to the fuelpump,..?? What are the fuel pressures..

Could be a 'puter, or sensor issue

 

[dubs283]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

sitting for three years??

you need to do a COMPLETE tune-up

plugs, wires, cap/rotor, fuel filters, ignition sensor (if applicable and never been replaced), check/set timing, fresh gas, etc...

coils do go bad, but on newer vintage ignitions it is rare for a coil to cause such major runnabilty issues - it does happen, but i rarely see coils go bad on newer packages

 

[BIGALF]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

My 5.7L EFI did the same and after all checks possible the last was the answer. The fuel screen at the end of the pick up tube in the tank got clogged as I ran in the water and strirred up the junk in the tank. I took the screen out and it now works great.

 

[jrivera]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

That cant be my issue bc I even disconnected the main pick up tube and put it directly into a small 8 gallon gas tank and it still did the same thing....

 

[jrivera]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

Come to think of it, I dont know if it will be a fuel issue bc theres plenty of gas being sprayed into the engine. The boat outside of the water with no strain rev's up to 6k but in the water, no more than 2k.

Also, theres no way it can be a cracked block or cracked head bc the compression would not be this good through all 8 cylinders and the oil would be kind of milky and its not.....

Someones gotta know why it rev's all the way up to 6k rpm's outside of the water with no load, and doesnt pass 2k rpm's while on the water.......

 

[Biged007]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

I have know idea on an I/O but I have had that prob on a couple of OMC's they incorporate an (engine saver) that severely retards the ignition when overheating could it be a bad sensor? I know it drove me nuts on a 90 Evenrude once

 

[jrivera]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

I have know idea on an I/O but I have had that prob on a couple of OMC's they incorporate an (engine saver) that severely retards the ignition when overheating could it be a bad sensor? I know it drove me nuts on a 90 Evenrude once

I am going to replace the TPS today and see what happens, I will keep you guys updated!!

Thanks for all the great feedback so far! I am not giving up on this boat! Its my 1st boat and it will not defeat me!!!! lol

 

[jrivera]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

***Bad News Update***

I installed the new TPS sensor today and when I went to crank her up, she would not crank..... I pulled out a spark plug, and low and behold, there was water in the cylinder...... As I removed each and every spark plug, there was water in each cylinder!!!!! That must have been that brown liquid coming out of the exhaust yesterday!!! This whole time, that must have been what it was, maybe started off w/ a small fracture and finally gave up yesterday.....

Could that be a bad head, block or head gasket?

I am taking out the head today to bring it to a machine shop to have it tested. If the head is good, than im thinking its going to be the block and not the head!

If the heads were bad this whole time, why did I get a good compression reading through all of the cylinders??? Im confused.....

Any suggestions???

 

[Bondo]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

I am taking out the head today to bring it to a machine shop to have it tested. If the head is good, than im thinking its going to be the block and not the head!

If the heads were bad this whole time, why did I get a good compression reading through all of the cylinders??? Im confused.....

Ayuh,... DON'T pull the head just yet...
Drain the cooling passages, block 'em off,+ pressurize with 15psi of Air...
You'll hear the leak, follow the sound to the crack....
Pull the head,+ your ability to test it is Gone...

Compression tests don't show up in cracked blocks,...
It's usually not cracked inside the combustion chambers, but elsewhere...

 

[Bud B]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

Been watching this with intent becasue I have a similar roblem with a 454 Im working on. Water in EVERY cylinder wouldnt be the head would it? more likely the intake manifold or gasket to leak in everywhere. EH??

 

[Bud B]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

Revving at 6K in neutral might do something too.

 

[jrivera]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

Ayuh,... DON'T pull the head just yet...
Drain the cooling passages, block 'em off,+ pressurize with 15psi of Air...
You'll hear the leak, follow the sound to the crack....
Pull the head,+ your ability to test it is Gone...

Compression tests don't show up in cracked blocks,...
It's usually not cracked inside the combustion chambers, but elsewhere...

Thats a great idea, I have not started to pull apart the motor yet. I will definitely try the leak down test first!

 

[jrivera]

Re: Mercruiser GM 350 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

Re: Mercruiser GM 350 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

Ok so I havent pulled apart the head or block yet.....Havent had time AND I still want more info/advice before I start to take apart the engine....... Taking it to a marine shop for repair is out of the question.....

I have replaced both manifolds and both risers (they were used), all 8 spark plugs, both injectors and rebuilt the throttle body. I tested the compression on all 8 cylinders and each of them were around 180psi about 3 weeks ago......

While on the water the engine bogs down when I push the throttle and will not go past 2k RPM's, but off the water on the trailer w/ the water hose hooked up, it easily goes over 2k RPM's...... It starts up w/ no problem and idles great......

Last week, we tried to start her up outside of the water and noticed there was water in all 8 cylinders the day after testing it in the water after replacing the TPS sensor and throttle body and injectors ......

From what I know and think, if the block or head were cracked, there would only be water in a couple of cylinders, NOT all 8 cylinders...... Am I pretty much on the right track assuming this...... Typically if water was able to get into all 8 cylinders, that can only be caused by a bad manifold and what else.......

Thank You All for your input!!!!!

 

[jrivera]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

I also went to Autozone to rent a leak down tester..... They said they dont know what that is...... They are saying that a compression tester is the same thing..... Can you hook up an air compressor to a compression tester to try the "leak down test" by putting air in each cylinder seperately to try to diagnose where the leak is......

 

[jrivera]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

Is there any way to test the manifolds for leaks.......

 

[01somta]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

Is there any way to test the manifolds for leaks.......

When you say manifolds are you talking about intake or exhaust? I have tested on turbo'ed race cars the intake side by putting a correct size rubber coupler to a piece of pvc with a pvc cap and a tire nipple (one way) and then putting like 15 psi in and letting it set to see if it leaks out (use a tire guage to check psi).

And I do believe the more expensive tester have the capablity to check compression and leak down, but the cheaper ones do not.

 

[Bud B]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

I wonder if you could have sucked exhaust water in there by racing it up in neutral. Closing the throttle at high rpm (you said 6k) creates a huge vaccuum.

 

[jrivera]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

When you say manifolds are you talking about intake or exhaust? I have tested on turbo'ed race cars the intake side by putting a correct size rubber coupler to a piece of pvc with a pvc cap and a tire nipple (one way) and then putting like 15 psi in and letting it set to see if it leaks out (use a tire guage to check psi).

And I do believe the more expensive tester have the capablity to check compression and leak down, but the cheaper ones do not.

What I meant was the exhaust manifolds/risers..... Is there any way to test the exhuast manifolds for cracks or leaks?

Would a cracked exhaust manifolds/risers cause water to get into the cylinders?

Would a cracked exhuast manifolds/risers cause the boat to bog down in the water when accelerating but not bog down off the water when accelerating???

 

[jrivera]

Re: Mercruiser 5.7L EFI Bogging Down from Idle to Full Throttle!!!!

I also performed the leak down test today and there was no indications of any leaks bc the needle did not move.....

I also performed another compression test today and the compression in all 8 cylinders were right back up to about 180psi in all 8 cylinders...

Could a bad intake manifold cause these issues......

Thanks