Post Complete tune up drivability problems

[Chris_94_Sprint_TX]

:frusty: :frusty: :frusty:
I did a complete tune up, changed plugs (gapped at .035), wires, cap, rotor, and point (all parts were from NAPAs marine catalog all in all about $1,000 in parts) and now when I take the boat out it runs fine for a few minutes then the points close up and it starts sputtering, surging, and popping through the carb. I didn't do anything to change the timing of the motor. I installed the point at the high lobe on the distributor shaft and it idles fine but then when I take it out it runs strong for about 15 minutes or so until I make a turn then it bogs down and starts sputtering, surging, and popping, if I come all the way off the throttle it stalls out. It also seems to run a little hotter than before too. Motor is an 85 Mercruiser 3.0L 140. Its done this to us twice and its starting to get annoying at $4 just to launch the boat for 15 or so minutes. Is there some break in procedure I am skipping here? Could bad gas be the culprit? I also changed the prop, installed a battery selector switch and a new fuel sending unit.

Any ideas guys, I'm loosing my mind here and my kids and niece and nephew are getting upset cause they think we're going tubing but end up getting let down.

Chris

 

[dubs283]

Re: Post Complete tune up drivability problems

I didn't do anything to change the timing of the motor

yes you did...

when you installed a new point set and didn't set the dwell - the timing WILL change, even if you change the points and set the dwell, the timing changes

that said, you MUST first set point dwell then set timing, otherwise you have no basis for troubleshooting other faculties...point being, get the ignition components dialed in, then start looking at other items

 

[theblob]

Re: Post Complete tune up drivability problems

Was it running like that before tune up? Did you replace fuel filter,because thats always a good idea when tuning up.the filter will cause it to bog and stall out.

 

[Chris_94_Sprint_TX]

Re: Post Complete tune up drivability problems

Was it running like that before tune up? Did you replace fuel filter,because thats always a good idea when tuning up.the filter will cause it to bog and stall out.

Ran great before but plugs looked bad (rusted and glazed on the hex head area) wires were in need of changing as well as cap and rotor. Cleaned then all up with sandpaper a few times so I figured it was time to change them. I looked at the filters and they looked real good, I cleaned the filter in the carb with B12. The paper filter in the pump is not discolored and you can blow through it extremely easy. Also sprayed B12 through it as well.

How do I set the dwell on the point? I am new to points and learning carbs. I was a mechanic but for autos instead of boats just never had any run ins with point set ups. I have a Seloc manual I will read through it tonight.

Chris

 

[achris]

Re: Post Complete tune up drivability problems

...How do I set the dwell on the point? I am new to points and learning carbs. I was a mechanic but for autos instead of boats just never had any run ins with point set ups. I have a Seloc manual I will read through it tonight.

Chris

seloc... :facepalm: Those things are not manuals...

Here's a proper manual for you.

https://docs.google.com/open?id=0B1TAvwZ3TjhfUVREOHFDUGZRR1NDelg5blYybmNRdw

To learn about points ignition systems...

How points ignition system works.

And...

How to tune your points ignition system

 

[Chris_94_Sprint_TX]

Re: Post Complete tune up drivability problems

I found the page in the seloc, looks like I missed a step.

Chris I have a decent grasp of the basics of how they work its just a matter of never having my hands on a set to see them before now. But, I will definitely read those links tonight too.

My question now is after I adjust the dwell do I need to go back and re-adjust the timing? or should that kind of correct itself?

Chris

 

[achris]

Re: Post Complete tune up drivability problems

.....My question now is after I adjust the dwell do I need to go back and re-adjust the timing? or should that kind of correct itself?

You set the gap/dwell BEFORE setting the timing.

Changing the gap/dwell will change the timing, but changing the timing will NOT change the gap/dwell....

HTH,

Chris.....

 

[oldjeep]

Re: Post Complete tune up drivability problems

:frusty: :frusty: :frusty:
I did a complete tune up, changed plugs (gapped at .035), wires, cap, rotor, and point (all parts were from NAPAs marine catalog all in all about $1,000 in parts)

Are you missing a decimal point in there somewhere?

plugs, wires, cap, rotor and points are maybe $100 worth of parts but even that would be over paying a bit.

 

[Chris_94_Sprint_TX]

Re: Post Complete tune up drivability problems

Not missing any decimal points.... Includes new starter, sending unit, tune up kit with plugs, wires, new prop, hub kit, battery selector switch, new battery cables, hydrofoil all totaled $1000. I may even be missing some items too.

Helps a lot Chris, thanks. Believe it or not I am an ASE master tech on cars, even certified on Dodge and Chevy trucks, Honda Civic, CRV, Accord and 3 series BMWs. But the boat is new water for me no pun intended. I think over the winter I will be converting to electronic ignition. I'm more familiar with it but I'm still deciding Flamethrower II or full MSD.

Chris

 

[Chris_94_Sprint_TX]

Re: Post Complete tune up drivability problems

So, I guess if timing is off it will cause the points to close up and not re-open? It seems that when all of this happens, after I get back to the house or open the dog house the points are completely closed regardless of lobes on dist shaft.

Chris

 

[achris]

Re: Post Complete tune up drivability problems

That would only happen if the screw holding the points down was loose.

The timing will not affect the points, at all...

 

[Eric 3.7LX Alpha 1]

Re: Post Complete tune up drivability problems

the bushings on the distributor shaft open the points back up.

When you set the point gap did you have the points contacting the "high Point" of the bushing so the points would be open at that time? Not trying to insult you just trying to get you going

 

[Chris_94_Sprint_TX]

Re: Post Complete tune up drivability problems

If I set the gap on the point does that set the dwell where it needs to be or do I actually have to put a meter on it? My meter does not test for dwell, still trying to locate a timing light, mine seems to have grown legs.

Chris

 

[Chris_94_Sprint_TX]

Re: Post Complete tune up drivability problems

the bushings on the distributor shaft open the points back up.

When you set the point gap did you have the points contacting the "high Point" of the bushing so the points would be open at that time? Not trying to insult you just trying to get you going

Yes I did, both time I turned the motor over till the points were on one of the high points on the bushing and set the gap at roughly 20 thousandths. hard to say though since my feeler gauges are missing.

Chris

 

[Maclin]

Re: Post Complete tune up drivability problems

Checking the dwell is a good system health check to perform, shows you what the engine "sees". If it is in range, you then just set the timing. If dwell is off then need to adjust the points gap again, rinse and repeat.