3.7 merc cruiser wont start

[Eric 3.7LX Alpha 1]

Re: 3.7 merc cruiser wont start

i also noticed my bolts for my motor mounts were loose. can i just tieten them up or how do u know were its suppose to be. i could move it 3/4 of an inch or so.

Be careful with the motor mount bolts, depending on which ones are loose you may throw off the alignment of the gimbal bearing and the outdrive. The motor mounts are adusted using an alignment bar thru the gimbal bearing into the coupler on the back of the engine.

Can you take a picture of them and post them up here so we can see which ones are loose?

 

[terrylittle]

Re: 3.7 merc cruiser wont start

actually all of them are loose, im going to repace all 4 bolts tommorrow. would i be able to put the drive on and just bolt the motor on tight, or would that do damage. also if i put the drive on and it bolts right up would the alighnment be good then. and do u think my starter could have caused my motor to stop. could it jam up .

 

[stonyloam]

Re: 3.7 merc cruiser wont start

OK, there are only 3 motor (engine) mount bolts on a 470, so I think we are talking about something else here. OH you mean the bolts that hold the front motor mount in place in the boat? The ones that go into the hull?

 

[terrylittle]

Re: 3.7 merc cruiser wont start

yea those ones

 

[terrylittle]

Re: 3.7 merc cruiser wont start

buy the way do u guys know what kind of block they are ? 3.7 but if i was looking for a starter out at the auto wrecker what kind of motor would i be trying to get the starter out of.

 

[stonyloam]

Re: 3.7 merc cruiser wont start

You can not use a auto starter in a boat, you need a marine rated starter. To do otherwise you risk a fire or worse.

Loose mount bolts can indicate structural problems with the boat, but that is far beyond anything in my knowledge base.

 

[terrylittle]

Re: 3.7 merc cruiser wont start

ok so no auto starter then.

 

[stonyloam]

Re: 3.7 merc cruiser wont start

OK trying to figure exactly where we are here. The outdrive is off right? did you pull the spark plugs? Does the engine turn over easily with the ratchet with the plugs out? The starter will not turn the engine over at all? What happens when you hit the start key? It did start and run when you took it out? That info will help.

 

[terrylittle]

Re: 3.7 merc cruiser wont start

yes the drive is off. yes the plugs are out. i had a hole in the hose at the back of the motor wich was spraying water out when it was running. i didnt notice till i took it out to the lake. so i shut it off and changed the hose. it was coming off i think its called the heat exchanger, where u pour antifreeze in but the big one at the back. after i got it changed i put my buddy on the tube and got about 5 min into it and bam the motor just died as i was driveing. it then wouldnt turn over it just sounded like the starter was screwed but i dont think it should have killed my motor. i took the starter out and tried it , it worked put it in and it doesnt turn the motor just like a grinding sound then it just clicks. i took the drive off wondering if something is jammed , it made no diffrence. took the plugs out and i can spin it with a ratchet seems good. i can here all the pistons moveing. with the key it just wont turn.

 

[Eric 3.7LX Alpha 1]

Re: 3.7 merc cruiser wont start

Ok so we have water spraying all over the place on the port side of the engine right near the exchanger and starter. Could water have gotten in the starter solenoid and caused it to malfunction? Trying to think what is electrical there.

 

[stonyloam]

Re: 3.7 merc cruiser wont start

Sounds like you might need a starter. You could take it in to an autoelectric shop and have it tested. Here is a reasonably priced one. I just put one in mine and so far so good. http://www.motorcityreman.com/memaoe5050502.html

When you blew the hose sounds like something got wet.

Were you able to tighten down the motor mount bolts?

 

[natemoore]

Re: 3.7 merc cruiser wont start

The small gear on the starter shaft that engages the flywheel actually slides forward and aft of the shaft. Either inertia, grooves cut in the shaft, or a solenoid makes the gear slide aft to engage the flywheel (can't remember), then a spring pushes it forward to disengage the flywheel after the key is returned from "start" to "on."

I wonder if water has gotten into that part of the starter and rusted it a little? When you bench tested it, could you see the small gear functioning as I described?

Also, a starter can still spin on the bench, but not have the torque to turn over the engine. Happened to me. Worked fine when it was cold, but after it warmed up, it lost torque and would barely even move the flywheel. Wonder if you could have some other "weak" starter problem.

It's pretty easy to eliminate the main starter solenoid by bypassing it using a remote starter. It's on the port side of the engine under the exhaust manifold near the front, then there's one on the starter itself which I'm not sure exactly how to test.

Anyway, the Mercruiser manual has a whole section on the starter. Have you downloaded it yet?

 

[hoot]

Re: 3.7 merc cruiser wont start

here is a thought, perhaps your alternator failed and the battery was powering the ignition and it drained down to where the motor stopped running, so now the battery is dead and won't turn the motor over. have you checked the battery? give it a charge and see what happens. how did you check the started and know that it is good?

 

[solar7647]

Re: 3.7 merc cruiser wont start

here is a thought, perhaps your alternator failed and the battery was powering the ignition and it drained down to where the motor stopped running, so now the battery is dead and won't turn the motor over. have you checked the battery? give it a charge and see what happens. how did you check the started and know that it is good?

I agree with this.

If you had water spraying back there you could have shorted something. Grab a different battery and try it. If you removed the starter from the engine it wont need alot of power to work, but if in the engine it needs the full power of the battery.

Hook up a new battery and maybe even a new cable from battery to starter, if it starts bring the rpm of the engine to about 1500 rpm and see what the voltage output is. If its dosnt read between 13-15 you have a bad regulator

let us know what you find.

FYI with all the plugs in it is hard to turn the engine by hand because each cylinder is producing around 150 psi.

Also the four bolts for the front mount in most cases pull out because of rotten wood so it may be difficult to get them to stay in.

 

[terrylittle]

Re: 3.7 merc cruiser wont start

im haveing the starter rebuilt right now, so when i get it back in i guess i will see the out come. also where are these flappers people talk about cause i never seen any on my boat. i did see a little rod trough one hose but no flapper. and if they were gone what will that do to my boat.

 

[solar7647]

Re: 3.7 merc cruiser wont start

im haveing the starter rebuilt right now, so when i get it back in i guess i will see the out come. also where are these flappers people talk about cause i never seen any on my boat. i did see a little rod trough one hose but no flapper. and if they were gone what will that do to my boat.

The flappers are inside the exhaust, they are number 6 on the below diagram.

 

[mdlee]

Re: 3.7 merc cruiser wont start

im haveing the starter rebuilt right now, so when i get it back in i guess i will see the out come. also where are these flappers people talk about cause i never seen any on my boat. i did see a little rod trough one hose but no flapper. and if they were gone what will that do to my boat.

I have seen a few big boats that didn't run flappers,,,,, I have none on my boat..... I have had no problams... not sure what it will do to your boat.... "the factory way is the best way".... If you have the exhaust apart and no flapers,,, you might want to put some in there

 

[solar7647]

Re: 3.7 merc cruiser wont start

The flappers prevent water from getting into the engine via the exhaust. They are located down stream from the point where water is discharged from the cooling system and would only effect that if they where stuck closed allowing the water discharge to flood the exhaust and engine with water.

The main purpose is to protect the engine in the event of a swamping...so say your ripping full WOT and you have to kill it or your engine stalls and you come to a stop really fast, as your wake swamps your stern the water has the possiblity to back flow up your exhaust. In this situation the pressure from the water will force the flappers to open and seal the pipe thus cutting off the path for the water to get up into the engine.

They dont have any effect on anything else.

 

[terrylittle]

Re: 3.7 merc cruiser wont start

thanks for the info on the flappers guys.

 

[terrylittle]

Re: 3.7 merc cruiser wont start

it was the starter rebuilt it and it fired right up. what happened was the starter must have seized engaged and actually stoped my motor. i didnt think that was possible but it is the only explanation.