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View Full Version : Boat warms up = No more idle?


Sledneck
05-25-2005, 09:57 PM
Just started this week-end.. Boat idles and runs great until after about 15mins when it warms up, it won't idle anymore... Still runs great at WOT or anything above 2,000rpm..

I was originally thinking the choke was sticking, but it's not..

The coil is hot to the touch.. I think this is probably my problem.. but why??

any ideas.?

6ballsisall
05-25-2005, 10:27 PM
Have you checked the timing?
Is the engine running rich?
Hows your plugs and wires?

Sledneck
05-25-2005, 11:02 PM
The timing was set when I installed the electronic ignition towards the end of last season..

I eleminated the ballast resistor /the instructions and upgraded to a 12v coil.. At this time I also replaced the cap and rotor..

I replaced the plugs at the start of this season (this was my second time out)

I don't think it's rich.. no black smoke, plugs look good..

The wires look good, the spray bottle test had no effect..

SKI*MC
05-25-2005, 11:15 PM
What kind of block? It sounds like a coil to me, electronic ingintion regires a lot more energy, maybe 12 V isnt enough.

jimmer2880
05-26-2005, 06:24 AM
Sounds electrical to me. Replace the coil to see if that works.

campbelljo
05-26-2005, 12:14 PM
Take your flame arrestor off and make sure that there is no fuel dripping into the venturies during idle. If so you could possibly need to adjust your floats or accelerator pump. This is unlikely to occur out of the blue, don't know if you have been tinkering with your carb?

robisjo
05-26-2005, 12:37 PM
I had the same problem with my '85 a few years back. I was running the standard Holley four-barrel. After spending $800 for the mechanic to test everything including vapor lock, it turned out to be a spring loaded idle set screw. When the motor warmed to running temp, the spring expanded and changed the idle adjustments so it would not idle however it ran great. They changed out the screw and I never had anymore issues with it.

Sledneck
06-06-2005, 12:06 AM
New coil, new wires, had the carb rebuilt, checked the timing..

I can't duplicate the problem in the driveway on the fake-a-lake.. only out on the water.. boat runs and idles A-1 for about an hour from cold.. Then coughs out, and will not idle.. fires right back up, idles for a few seconds then dies..

help..

JimN
06-06-2005, 12:10 AM
I had a mustard bottle filled with gas for situations like this. If it didn't want to run, I would add some gas. If it ran better, I knew that the carb needed work. Make sure the flame arrestor is clean.

Sledneck
06-06-2005, 11:25 AM
I thought I had it licked when I cleaned out the flame arrestor Saturday, but no dice, although it needed a good clean anyway.. I'll pack some extra mustard next week-end, good tip.. thanks..

JimN
06-06-2005, 07:23 PM
Make sure you have a fire extinguisher nearby when you add gas with any kind of container. Don't use ether.

dwvktm450
06-06-2005, 07:51 PM
I just put an electronic ignition in my 83. Mine would run great at WOT and would not idle at all. It also ran great in the driveway before I went to the ramp. See the similarities. My electronic ignition instructions gave the part number for a coil to run if the stock one did not have enough ohms when tested. (need a fluke to test that), as well as bypassing the resistor. When my boat did not idle I came back and put the coil in and checked the gap on the electronic ignition. The boat idles and starts better than before after the two adjustments. Your symptoms sounded a whole lot like mine and I could not help but respond. I hope this helps.

Sledneck
06-06-2005, 08:29 PM
I'm leaning towards ignition perhaps the electronic module itself is bad.? I noticed they sell replacements..?

Funny you mention that as an ex-electronics technican I actually do own a Fluke. Anyway, I tested the coil, and swaped it for a 12v coil per the instructions.. This set-up worked fantastic last season..

What coil did you end up going w/..? Did you get your kit from SKIDIM..?

What's the gap supposed to be set at.? The kit originally came w/ a little red mickeymouse feeler gauge type thing that, yup you guessed it.. I pitched w/ the directions.. :uglyhamme

BriEOD
06-06-2005, 08:57 PM
Sledneck,

When I was talking to Vince at Ski DIM last week we were talking about intake manifold gaskets. He told me that the 351 needed a marine gasket set for the intake. Apparently the standard automotive ones cause some problems. This is a quote from their site: "A restrictor (smaller hole) in this gasket reduces the amount of exhaust gas that flows across the manifold thereby heating the manifold which had been causing the carb to boil fuel and caused hard re-starts (vapor locking) and IDLE INCONSISTENCY." http://www.skidim.com/prodinfo.asp?number=RM0186

Have you had the intake off recently?

Sledneck
06-13-2005, 12:23 AM
I just put an electronic ignition in my 83. Mine would run great at WOT and would not idle at all. It also ran great in the driveway before I went to the ramp. See the similarities. My electronic ignition instructions gave the part number for a coil to run if the stock one did not have enough ohms when tested. (need a fluke to test that), as well as bypassing the resistor. When my boat did not idle I came back and put the coil in and checked the gap on the electronic ignition. The boat idles and starts better than before after the two adjustments. Your symptoms sounded a whole lot like mine and I could not help but respond. I hope this helps.

Thanks dwvktm450.! You're post got the wheels turning put the ballast resistor back in, vola! no more problems....!

JasonW
05-27-2006, 02:52 PM
The timing was set when I installed the electronic ignition towards the end of last season..

I eleminated the ballast resistor /the instructions and upgraded to a 12v coil.. At this time I also replaced the cap and rotor..

I replaced the plugs at the start of this season (this was my second time out)

I don't think it's rich.. no black smoke, plugs look good..

The wires look good, the spray bottle test had no effect..
Can you please point me to the instructions for getting rid of the ballast resistor and going with a 12V coil?

Thanks!

JimN
05-27-2006, 02:58 PM
If you have a ballast resistor, you already have the 12V coil. Points can't handle 12V and that's the reason for the resistor. It creates a voltage drop and they last a lot longer. OTOH, they're contact points and every time they make contact, they arc and burn slightly.

I sold a conversion kit to someone last week and when he started it, it ran for about 5 sec and shut off. His timing was way off and once he changed it, everything was OK. Don't expect teh timing to be the same as when the points were in tehre.

JasonW
05-27-2006, 07:46 PM
Sounds like I should leave everything as it is :) I'm getting ready to take the boat out for the first time this year. Last year it started/idled/ran great up until mid-throttle. Then it started dogging out.
I don't imagine it magically fixed itself while sitting over the winter. After I take it out I'll report back and hopefully someone will have the insight I need!

Thanks!

And JimN, I replied to the other thread before reading your comment on the 12V coil here! Thanks for the info.