No Start, but should

[Ng321]

3.0 Mercruiser fresh rebuild. Compression around 200 psi in all clyinders, spark at every spark plug, timing set to 1 degree BTDC like the cover says, carb is new and properly squirting fuel, battery full and new starter. When I crank it the engine cranks strong and then after 2 seconds it sound like its trying to fire and I will hear a couple pops at the exhaust. When I let off the key the boat sounds like its running for half a second the dies. I have no more ideas.

 

[Bt Doctur]

how did you time the motor for #1 TDC compression and how did you install the dist. firing order is 1,3,4,2

 

[Ng321]

.

 

[Ng321]

how did you time the motor for #1 TDC compression and how did you install the dist. firing order is 1,3,4,2

I followed the timing procedure in the manual and used a timing light the adjust the timing while cranking it. The distributor was initially lined up with the marks from the factory and adjusted the timing starting from there. The spark plug wires go to the correct spark plugs i checked

 

[tank1949]

"Pop" in exhaust??? Sounds like distributor went in incorrectly and out of time. Been there too! Pull valve cover and plugs and bring #1 cylinder up (blows your finger out of sp hole). Your timing mark on harmonic balancer should be in line with timing tab 0 mark. You may have to bump starter. You should be able to see intake rocker arm move open to allow gas/air mixture into cylinder and then the next cycle will be compression (make sure ignition is NOT connected.) Check if rotor points to #1. Easy to fix unless you put timing sprocket on incorrectly. I doubt that....

 

[Scott Danforth]

First, your gauge is most likely bad if you are getting 200psi. 150 would be max for a new motor

your dizzy is in 180 degrees out

 

[Ng321]

"Pop" in exhaust??? Sounds like distributor went in incorrectly and out of time. Been there too! Pull valve cover and plugs and bring #1 cylinder up (blows your finger out of sp hole). Your timing mark on harmonic balancer should be in line with timing tab 0 mark. You may have to bump starter. You should be able to see intake rocker arm move open to allow gas/air mixture into cylinder and then the next cycle will be compression (make sure ignition is NOT connected.) Check if rotor points to #1. Easy to fix unless you put timing sprocket on incorrectly. I doubt that....

Rechecked the distributor pointing at #1 at tdc and it does. I say a video on YouTube where the guy didn't do the special timing procedure he just set it to 8 degrees BTDC and it fired right up. Guess I'll give it a shot. BTDC can't hurt much.

 

[Scott Danforth]

your distributor may be pointing to cylinder #1, however its pointing to it on the exhaust stroke, not the intake stroke. pull dizzy, turn motor over 360 degrees and re-stab

on a 3.0, a few degrees advance will cause detonation under load.

 

[isaacs]

Are you sure your lanyard safety switch is hooked up and functioning properly? My boat will try to start as long as the key is in the "start" position, then immediately die upon the key's release if the switch is flipped.

 

[Ng321]

Are you sure your lanyard safety switch is hooked up and functioning properly? My boat will try to start as long as the key is in the "start" position, then immediately die upon the key's release if the switch is flipped.

I dont have a reason to believe that is the issue but I will try that tomorrow. About to give up and wait the 3 weeks for the shop to look at it

 

[Scott Danforth]

you dont need the shop to look at it. you need to look at post #8

 

[matt167]

Ditto on Scott's advice. It's most likely 180* out. Been there a time or 2

 

[Ng321]

Update: tried 360 degree rotation of the distributor at TDC, result: backfires through carb. Verified tdc at #1 clyinder with a compression gauge and set distributor at #1 spark plug, result is firing but not starting. While cranking with killswitch engaged does not fire, fires when kill switch not engaged.

 

[Bondo]

Update: tried 360 degree rotation of the distributor at TDC, result: backfires through carb. Verified tdc at #1 clyinder with a compression gauge and set distributor at #1 spark plug, result is firing but not starting. While cranking with killswitch engaged does not fire, fires when kill switch not engaged.

Ayuh,..... Welcome Aboard,...... Have ya verified that it's gettin' gas,..??

Have ya tried splashin' abit of fuel down the carb's throat,..??

 

[Ng321]

Ayuh,..... Welcome Aboard,...... Have ya verified that it's gettin' gas,..??

Have ya tried splashin' abit of fuel down the carb's throat,..??

It's for sure getting fuel. The accelerator pump sprays fine too when I prime it. Then the engine does sound like its firing just not staying running

 

[QBhoy]

Couple of things.
your gauge is off a fair bit
You could be out on the timing by half (as in you’ve set it on the off rotation)
Or your fuel is rubbish. Suspect the rotation of the engine is out though. Your on the wrong cycle

 

[Scott06]

Have you looked at the spark with a spark gap tester? You may have a spark but is it strong enough to light the fuel. spray a touch of starting fluid down the carb -if that doesnt light off you are loosing spark strength somehwere. If it does light off and run till the starting fluid is gone would think you have a fuel quality or quanitity issue