Troubleshooting tips, fuel or electrical? A little long.

[aogmitch]

First post here. First, a little history on my boat. Picked me up an '86 Sea Ox 230C a month and a half ago. Originally ran a AQ200D with a 290 Out drive, which has been converted to a DuoProp. Outdrive was rebuilt by the prior owner, and the 305 was replaced with a rebuilt 350 in spring of 2012. Motor is FWC with a crank driven sea water pump. Never owned or worked with I/O before, so I have actually been learning alot from this site. First voyage, boat ran well with temps about 140 deg on the gauge, for about two hours. When I got back to the no wake zone and headed for the docks, temp shot up to 190 then hit 200 (gauge max) by the time I made it back. Not to drag this out, but turned out that cyls 5 and 6 were cracked and water was getting in the motor, and had been for some time, as I found the cyls had corroded and pitted from water setting in them.

Since then, I have installed a new 350 long block, new impeller, new risers and manifolds, had heat exchanger boiled, tested, and internal leak repaired, new points, condenser, cap, rotor and wires. Maiden voyage with new motor started well last Friday. New motor ran smooth and no temp problems.
Then it went down hill after a couple hours. Motor seemed to be not getting fuel. Couldn't get above 2500 rpm without it trying to die out, backfire and cough (running the original Rochester 2bbl which was supposedly rebuilt last year also). First thought was fuel filter. Its running a Racor 320. Got boat home, bought a new filter and installed. I rechecked the points, dwell and timing and all were were they had been originally set.

Took boat out again yesterday and ran sweet for the first hour, then problem came back. Sat for about an hour letting the crab pots soak, started boat and it was running well again. By the time we checked and reset, problem came back. When it was time to head back, about 2400 was the most I could get and keep it running. Half way back, I noticed the engine sound smoother again, so pushed the stick fwd and all was well again.

Would this be fuel pump? Could the coil be causing me issues? Not sure where to go without starting to throw money at it. Suggestions?

 

[glenn property of pam]

Re: Troubleshooting tips, fuel or electrical? A little long.

problem seems to present when engine is hot but runs ok when cool. Problem is also low speed with backfiring.

Hmm sounds like timing, coil or resistor wire to coil (low voltage at the coil). But that's a guess as backfiring means fuel has been allowed past the cylinders into the exhaust with out being burnt and you said the timing was checked so that points to the coil.
I would test all leads with the timing light just to make sure there's a spark then warm up the motor and test again.
(educated guess but its a place to start)

p.s stuck choke would also do the same thing

 

[aogmitch]

Re: Troubleshooting tips, fuel or electrical? A little long.

Should the resistor allow 12v to the coil, or will it be less?

 

[glenn property of pam]

Re: Troubleshooting tips, fuel or electrical? A little long.

Should the resistor allow 12v to the coil, or will it be less?

external resistor type coil I think is around 8v but don't quote me on that (when running, may be 12v when cranking). Internal resistor should be 12v with no resistor wire so if a new coil was fitted and it says internal that could be a problem.

 

[aogmitch]

Re: Troubleshooting tips, fuel or electrical? A little long.

Still has the external coil with what appears to be the original VP coil from '86.

 

[glenn property of pam]

Re: Troubleshooting tips, fuel or electrical? A little long.

you have a timing light that you can use to see if the leads are sparking so just do a cold and warm test to see if you have a spark when the motor is warm. Also check to make sure the choke plate is open when the motor is warm.

 

[bruceb58]

Re: Troubleshooting tips, fuel or electrical? A little long.

Could also be a fuel venting issue. After running for awhile, you may be developing a vacuum in the tank. Try opening the fuel fill opening next time.

Might also be worth putting in a fuel pressure gauge between the fuel pump and the carb and checking for spark when your engine dies like glen said.

Not that this is the issue but you did set the dwell with a dwell meter and timing with a timing light right? Pull a plug or two to see what they look like when the engine dies. Would be interesting to see if they are wet with fuel or look like something went lean on you.

 

[aogmitch]

Re: Troubleshooting tips, fuel or electrical? A little long.

Timing and dwell set by light and meter. Timing 8 BTDC, and dwell is 30. Just checked voltages and with engine running, alt output is 14.2. Batterys are seeing 13.6, input to resister is 12.2, output of resistor to coil is 10.7. I also have one bad battery. Draining its self quickly. Disconnected all cables to it and still discharging.

 

[dypcdiver]

Re: Troubleshooting tips, fuel or electrical? A little long.

Just a quick question, when you say the Rochester 2bbl was rebuilt, was it done to 305 or to 350 spec as the jets and setting might be different. Check the part number of the 305 and 350 carbs for any differences.

 

[aogmitch]

Re: Troubleshooting tips, fuel or electrical? A little long.

The only difference between the two, and I'm just taking a stab in the dark at this, would possibly be the main jets could be larger for the 350. All else should be the same between the two. I'm assuming that the prior owner reinstalled the same mains that were in there originally. When the boat decides to not act up, the carb works great and everything is smooth in all throttle positions. Idles great, no flat spots or trying to die when going into gear or anything. Starts easy cold also. Even when its acting up, idle and the first 2000 rpm work good. I think if it ran like garbage all the time it would make things easier to troubleshoot. The come and go problems suck to chase down.

 

[aogmitch]

Re: Troubleshooting tips, fuel or electrical? A little long.

Checked fuel lines and tank vent. All good. Changed filter again, not seeing any water in gas. Blew from filter connection to tank, doesent appear to have any blockage. Boat runs great fo 80% of the time. But when it starts acting up, idle gets bad, will have a hard time staying running going into gear, hard starting issues and can't get it above 2400 rpm. Then it will start running great again for quite awhile. Problem seems to come when ideling for awhile most the time. Will a mech. fuel pump cause intermittent problems? Haven't checked fuel pressure yet.

 

[aogmitch]

Re: Troubleshooting tips, fuel or electrical? A little long.

Just wanted to update my issue. I may have just been chasing a water in fuel and/or old gas problem. After checking all the easy, no cost items like fuel pick up, vent etc., and a couple more filter changes. Boat is doing much better now. Was out on the water all day yesterday and didn't have a single issue with anything. Motor ran flawless all day.