Mercruiser 470 3.7L Ive got fuel and spark still wont run

[cclements716]

I have good spark and fuel but it still wont run. I can NOT even get it running on ether. The only thing else i thought it could be would be the timing...??? What are yalls thoughts? Thanks

 

[Don S]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

What did you do since it ran last? Did you mean you CAN'T get it running on either? or that it would start using either?

 

[Joshua Nichols]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

Hmmm compression? Ever heard fuel, spark and compression? You have spark where? At the coil or the plugs

 

[cclements716]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

I jut bought it. I would say they have done nothing. I have put on a new starter, new alternator, cleaned all the wires on the entire engine, put in new plugs and cleaned the carb. It will spin over and act like it wants to run but it will never take off. It will be right on the verge (a few pistons taking off type of sound) but it will not run. I even sprayed a little ether in it and still nothing.

 

[cclements716]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

It definitely has compression. I have spark at the plugs. Bright blue spark.

 

[flamron]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

Fresh fuel?

I just had a problem with my generator this winter. Tried to start it, but it would just turn over. Drained gas and new fuel put in and it fired on the first pull.

Good luck!

 

[86 century]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

Have you tested the compression if so what are the numbers.

Next the timing; pull #1 plug rotate eng till piston is as close to top as possible. Remove dist cap make sure rotor is pointing at or near where the #1 plug wire sets it is possible for it to be 180deg out as well.

Check these thing out and let us know what you find.

good luck

 

[Joshua Nichols]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

It definitely has compression. I have spark at the plugs. Bright blue spark.

Have ya put a gauge on her yet.....

 

[Don S]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

It definitely has compression. I have spark at the plugs. Bright blue spark.

Compression has nothing to do with spark.
Here is a link to a Mercruiser service bulletin on how to properly do a compression test.
http://www.boatfix.com/merc/Bullet/97/97_25.pdf

Since you just bought it, I have to ask, have you ever run an engine with a carb on it before.

Since you just rebuilt the carb, are you sure you rebuilt it it correctly, did you prime the carb, can you operate the throttle and get gas out of the accelerator pump outlet into the throttle bores?

 

[dn010]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

What about timing!? If your distributor has been installed our adjusted wrong then you won't be running. Same with timing chain.

 

[cclements716]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

I have not tested compression but i know it has it. If i turn it over with all the plugs in there is a speed difference from when i pull all of the plugs and turn it over. I did check the distributor in regards to position. This may seam like a stupid question but is the #1 cylinder the first from the front (pulley side) or the rear (flywheel). I was under the assumption that it is the pulley side. If that is the case then i think that i have the wire and the orientation of the cap in the correct position. At this point i am thinking that the cap is just out of timing and not letting it take off. I did not rebuild the carb my self. i brought it to a local marine mechanic. I did have a caravelle interceptor before this boat but it had the thunderbolt ignition and never had a problem with it.

 

[Bondo]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

This may seam like a stupid question but is the #1 cylinder the first from the front (pulley side)

Yes....


'n prime it with Gasoline, Not ether....

 

[Joshua Nichols]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

I have not tested compression but i know it has it. If i turn it over with all the plugs in there is a speed difference from when i pull all of the plugs and turn it over.

Wow that's a compression test? That must be a new way to check it.... So if it has a dead cylinder it's going to run?:facepalm:

When you change out the wires and plugs you did it one at a time correct?(I guess not since you have had all the plugs out) Some people get the wires all outta whack and then for sure have a starting issue..
BTW go buy a compression gauge.. If you don't wanta purchase one then auto parts store might loan one out (IDK I have always had one)... Do a compression test by advice giving in previous post by Don.. You could have a valve sticking in 2 cylinders.. Guess what.. Won't start like that but will give you the perception that it has compression if you look at the way you see it...

Have you ever seen this engine run?

 

[cclements716]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

I have not seen it run. it has not been run in a year or so. I do need to do a compression test. I have traced all the wires and i did change them one by one. I have taken the valve cover off and all of the rockers were rocking. Would that signal that the valves were working properly?

 

[Joshua Nichols]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

I would say it's tough to really say anymore till ya get some compression numbers... Then maybe a leak down test..

 

[Don S]

Re: Mercruiser 470 3.7L Ive got fuel and spark still wont run

The front cylinder is #1, the flywheel end is #4.

Let's assume for a minute the compression is not the problem, if the previous owner had the distributor out and put it back in in a different location, following any manual drawings about how the plug wires are set is a waste of time. You have to get #1 cylinder up on TDC on the Compression (firing) stroke. Then look at the rotor, it will then be pointing at where #1 spark plug wire should be. Then just follow in the direction of rotor rotation with the rest of the plug wires and the firing order.

Here is how you find #1 TDC on the compression stroke.
http://forums.iboats.com/showthread.php?t=427081