Could back pressure cause hard starting?

[surrender]

Ok got to run in the water after new tach install. Note: carbs have been rebuilt, new filter and fuel lines new fuel.

Boat was hard to start, starter would turn engine over then disingage. I thought it was due to back pressure and when I tilted it out of water she turned over and fired off quickly. Batttery is fully charged(only two weeks old) I'll check connections again. Boat ran good, with two on board ran up to 5300 rpms, 32.8 mph. All good. Went to pick up a buddy in a creek and idleing down his creek boat was dropping rpm slowly. By the time we got to his house it stalled out. Ended up having to adjust idle up to get it to run. Checked timing with light at idle and it would only run if it was around 8 degrees with the idle screw turned in alot. Primer bulb would not stay hard all the time. Have to check all lines for leaks. A note: Coils all look bad, cracks and gouges in them. Could boat get to running warm and coils heat up and start cutting out? I can get my hands on 4 used good coild for $40. I think I'll change all four and try agoain. Any other thoughts. Ran boat back to ramp and it seemed ok but would hestitate at first and then run good but only to right at 5000 rpm. Go home and it was running at 2000 rpm on muffs on trailer. Readjusted timing back to where it was and idle also. My thoughts are power pack or coils.

 

[JB]

Re: Could back pressure cause hard starting?

I am wondering what outboard you are talking about.

 

[surrender]

Re: Could back pressure cause hard starting?

1996 Johnson 88 Special

 

[jbjennings]

Re: Could back pressure cause hard starting?

Coils can most defiinitely heat up and get an open circuit in their windings. Cracks in coils are usually a good indication they're bad.
Idle will definitely be higher on muffs with no back pressure, so you should set idle on the lake. You should check for good spark with a $6 autozone spark tester, and fix accordingly.
Hope this helps,
JBJ

 

[bktheking]

Re: Could back pressure cause hard starting?

I think you are doing yourself a favour, cracked coil aren't good.

 

[James R]

Re: Could back pressure cause hard starting?

Sounds like fuel pump to me.

 

[jtexas]

Re: Could back pressure cause hard starting?

"Could back pressure cause hard starting?" yes, but...

...it is harder to start the motor with submerged exhaust, but that's normal. It would be more precise to say, "lack of backpressure causes easy starting".

What I mean is, the hard starting is a symptom, and the cause is something other than backpressure -- most likely either compression, spark or fuel. Or some combination.

The primer bulb has to stay firm...no matter what else is going on in there, if you're losing fuel pressure it won't run right.

The pressure drop could be masking other symptoms, so you've got to deal with it first. Could be sucking air around the fuel line fittings, faulty primer bulb, perforated diaphram in the fuel pump (which btw could be leaking fuel into the manifold flooding a cylinder, causing your symptoms).

This is a good time to do a compression test and spark test.

 

[surrender]

Re: Could back pressure cause hard starting?

Fuel pump has new diaphram, all new fuel lines from tank to motor and under cowl lines changed to. The only lines not changed were the small ones leading to the primer. Primer bulb is new. When I say hard to start it is not like it turns over and over for ever before starting. It will turn over a few times then the starter disingages from the flywhell and it stops. It really doesnt do that when out of the water on the muffs. Once it has been running for a while in the water I can shut dopwn and restart fine even after sitting for a while. By the way compression was good 107-112 all around.

 

[surrender]

Re: Could back pressure cause hard starting?

I pulled the silencer off the front of the carbs and pumped the primer bulb and alot of fuel came spilling out of the lower carb. Pulled carbs and top was ok, bottom had a float which needed adjustment. Put all back together and pumped bulb, no fuel out of carbs and it stayed hard. Motor started and sounded good. Gonna put in water this week and test again. Did notice on upper carb what was a little gunk(whiteish) in one nozzle. All cleaned now. Must have been a little water left in tank. Thought we cleaned it out good. Will change fuel water seperator again. Motor was definitly smoother on the muffs, hope it is all good in water.

 

[Gary H NC]

Re: Could back pressure cause hard starting?

Those cracked coils are still going to be an issue sooner or later.
I have seen coils look perfect and still arc to ground right through the side of them.
Run the engine in the dark on the muffs and have a look....

 

[surrender]

Re: Could back pressure cause hard starting?

Sorry Gary. I forgot to mention I changed all four coils. go spark out of all. they are used but the place I bought them garanteed them. They want me to run boat a few times to be sure their good after the motor warms up. No cracks , they look pretty new.

 

[James R]

Re: Could back pressure cause hard starting?

These motors can be finicky. The synchronization must be correct in the first place. Adjust idle speed to 1200 to 1400 on the muffs, with a final set up in the water with the motor in forward gear to 700 to 800, at least so the motor does not stall when put in gear. These adjustments should solve your problem.