Merc 5.7L LX with Governor???

[Don S]

Re: Merc 5.7L LX with Governor???

Something I just found in a 96 Merc recertification manual. Seems if you try to use the Bravo ICM on an Alpha, it will drop the rpm down to 3400 rpm. Now that was with a T1 module, perhaps yours is the same.
Take it for a run and disconnect the shift interrupt switch and see if your rpms come up. NOTE: You WILL have to plug the shift interrupt switch back in to get it to come out of gear, so be prepared.

It's worth a try anyway.

 

[Mjust]

Re: Merc 5.7L LX with Governor???

Just realized something. You have the 1.62 Gear ratio, that is for a V6, not a V8. You should have the 1.47 and even then the 21 pitch prop may not be enough.
Since you are using that prop with the 1.62 drive, you ARE hitting the rev limiter, and your tach is off, and you will have a hard time planing cause you don't have the speed.

Don,

Say my tach is off, with out spending a fortune to change the gearing, if I went to a 23 Pitch 3 Blade or 4 Blade will I have the speed then to get out of the hole??? From my understanding going up in pitch from 21 to 23 will make it more difficult to take of to plane.

 

[Don S]

Re: Merc 5.7L LX with Governor???

Do the module/shift interrupt test I just mentioned before you go repropping. You also need to find a good shop tach to check rpms with. Rather an induction tach in a timing light or something, but you MUST know what your rpms are before messing with the props.

 

[paulrfrancisco]

Re: Merc 5.7L LX with Governor???

Lets not forget that from a weight perspective, he now has a heavier engine... Although more hp. 260 hp on an 18 foot boat is likely going to stand it right up on the transom to get out of the hole... Just to be sure, check that your outdrive trim is, in fact, going all the way down... Have you observed it trimming up and down while on the trailer...? Also, after reading all these threads, IMHO it sounds like the gear ratio problem on the drive, and a def. tack...

 

[Mjust]

Re: Merc 5.7L LX with Governor???

Lets not forget that from a weight perspective, he now has a heavier engine... Although more hp. 260 hp on an 18 foot boat is likely going to stand it right up on the transom to get out of the hole... Just to be sure, check that your outdrive trim is, in fact, going all the way down... Have you observed it trimming up and down while on the trailer...? Also, after reading all these threads, IMHO it sounds like the gear ratio problem on the drive, and a def. tack...

I do know the trim is working and have observed it. I do need to figure out where I have a water leak into my trim fluid. I noticed the fluid resivor had a tan milky fluid so I drained it out of the system and refilled with new fluid. After running the boat all weekend I check it again an it was showing water in it again. A friend of mine told me to change the steel braided hoses on the out drive since there notorious for leaking.

 

[Mjust]

Re: Merc 5.7L LX with Governor???

So here is my next question, What is the difference between the 96 5.7L LX Alpha motor and the 96 5.7L LX Bravo Motor??

 

[John_S]

Re: Merc 5.7L LX with Governor???

Mjust,

Allot of people have put time and effort into trying to solve/understand your problem. Please, lets take it to conclusion on the rpm rev limiter issue, before moving back to the hole shot issue. Please put a tach on it, to find out what rpm it is really hitting the limiter. The info that Don provided on the Bravo ICM, you would not have found in a hundred hours of backyard diagnostics. Won't find that in any service manual, either. Perform the test.

Now, once you have that solved move back to you hole shot problem. Fix the water in the trim system problem first.


"What is the difference between the 96 5.7L LX Alpha motor and the 96 5.7L LX Bravo Motor??"

On the engine side, probably just the ICM. But you can spend some hours on the Merc part website to verify.

 

[Mjust]

Re: Merc 5.7L LX with Governor???

Something I just found in a 96 Merc recertification manual. Seems if you try to use the Bravo ICM on an Alpha, it will drop the rpm down to 3400 rpm. Now that was with a T1 module, perhaps yours is the same.
Take it for a run and disconnect the shift interrupt switch and see if your rpms come up. NOTE: You WILL have to plug the shift interrupt switch back in to get it to come out of gear, so be prepared.

It's worth a try anyway.

Don,

Where is this shift interrupt switch so I know what to do??

 

[Mjust]

Re: Merc 5.7L LX with Governor???

The serial number on the engine is 0K158997

 

[Bry21317]

Re: Merc 5.7L LX with Governor???

Just so you know also, I have 95 Chevy 5.0 Liter with the Alpha 1 with 1.65R gears. Its on a heavy boat, 94 Crownline 19 foot bowrider, about 2800lbs. It will spin a 21 pitch prop all the way up to 5000 without thinking twice, with a full load. I also put a 23 prop on mine, and its still comes out of the hole quick, just slowed down on the top side. I lost about 6 mph and 800 rpms, and the two props were the identica brand, just different Pitch only.

I would make sure you do as they have asked, Check your Tach first and then do as Don Stated and check the Shift Interuptor. You will ge great information on here, but you must do as they ask and report back to them. Its l ike trying to fix a computer over the phone, very hard without it in front of you.

Good luck, I am interested to see what you find.

Bryan

 

[Mjust]

Re: Merc 5.7L LX with Governor???

I do appreciate all the help guys and I did get a shop tach and will find out what the true RPMs are and report back to you ASAP. I will check the shift interupt as Don requested but I know that I dont have the T1 ICM module cause the T1 has two wire connection ports where my ICM only has one.

 

[John_S]

Re: Merc 5.7L LX with Governor???

"Where is this shift interrupt switch so I know what to do??"

It is on your starboard elbow. It is a micro switch mounted on the plate the shift cables come into. You should see two wires that come off to bullet connectors by your valve cover.

PS: Recommend getting Merc Service Manual #17 for your engine. It is not online But the drive is http://www.boatfix.com/merc/Servmanl/14/14cover.pdf