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View Full Version : Engine stumbles badly after a few passes?


ultrastryk
03-29-2012, 10:36 AM
As spring approaches I need to fix a problem that started last fall. I have a 1997 with the GT-40. Boat starts fine, runs fine at first. Then after making a pass or two, really stumbles badly. I have to feather the throttle back and forth just to make it back to the dock. If I wait a few hours and head back out, it does the same thing. I changed the fuel filter (which is one of those cell type that has the electric pump in it). No change. Could it be crap in the tank from years of the ethanol, is clogging a filter in the tank? One of the fuel pumps? Thanks for any help.

Bill

DooSPX
03-29-2012, 10:49 AM
Wait? What? I take it we are not talking about a MC here, correct? That's no biggie, just trying to get some facts straight. MC switched to chevy full time in 94. I believe CC used ford up to 99? We are talking about a EFI ford right? In a CC? It could be gunk clogging the filter. It could be a sensor? IAT possibly. or a pump after it gets hot starting to fail? How much fuel in the tank when it happens? In cars, fuel pumps do not like to be ran really low, they get hot and burn up.

BrianM
03-29-2012, 10:52 AM
I'd start by replacing the fuel filter.

Double D
03-29-2012, 11:11 AM
As spring approaches I need to fix a problem that started last fall. I have a 1997 with the GT-40. Boat starts fine, runs fine at first. Then after making a pass or two, really stumbles badly. I have to feather the throttle back and forth just to make it back to the dock. If I wait a few hours and head back out, it does the same thing. I changed the fuel filter (which is one of those cell type that has the electric pump in it). No change. Could it be crap in the tank from years of the ethanol, is clogging a filter in the tank? One of the fuel pumps? Thanks for any help.

Bill

I have been through something similar but with my Indmar. How does the engine act when it goes to crap? I doubt its the same thing but you never know....

Jeff d
03-29-2012, 12:40 PM
Next time it does it open your gas cap and see if the tank sucks air. It's a long shot but if your vent is kinked or plugged up your fuel pump could be creating a vacuum in the tank which eventually becomes too much for your fuel pump to draw against.

j.mccreight@hotmail.com
03-29-2012, 08:33 PM
Distributor ignition module is prolly bad, I had the same issue on old 95 efi 5.0 f150 , it would run fine cold but when it warmed up it stumble and try to die. I went through the fuel system before changing the ignition module ran fine after...

mikeg205
03-29-2012, 08:47 PM
check the ecm should indicate misfire... which IMO supports j.c's point...

j.mccreight@hotmail.com
03-29-2012, 09:50 PM
check the ecm should indicate misfire... which IMO supports j.c's point...

Mine never set a code, if it did it would have been easier to diagnosis...

ultrastryk
04-04-2012, 09:33 PM
No, the boat is a MB Sports Pro190. I figured there were alot of MC's out there with this powertrain. Is the ignition module in the distributor or on the plate at the back of the motor that the various circuit breakers are on?
Thanks
Bill

j.mccreight@hotmail.com
04-04-2012, 09:47 PM
On a truck, its mounted on the distributor itself I would think the marine version would be similar, iirc you need a special type of torx to remove it also be sure to apply some dielectric grease between the module and its mount...

http://item.mobileweb.ebay.com/viewitem?itemId=370279397190&siteId=0&isClassified=false

east tx skier
04-04-2012, 10:59 PM
Bill, are you running a PCM GT-40, i.e. a multiport fuel injected GT40? Or is it a carbureted 351 with GT40 heads?

With the former, fuel pressure is everything. And, generally, a drop in fuel pressure causes most of the issues with that engine.

MasterCraft never ran this engine. I have a 98 Correct Craft SN with the engine.

What you're describing sounds an awful lot like what happened to me at the end of the season two years ago. Diagnosing it is probably tricky. So I'd suggest fixing it and seeing if the problem goes away. On top of your fuel tank, there is probably a right angled brass antisiphon valve on the fuel send line. Remove the fuel hose and valve and replace it (they run about $11). Use pipe dope to get a good seal. Reattach the fuel line. There should be a return line on the tank as well (assuming I have the engine right). Hopefully, somebody at MB put corresponding tape on the send line and at the fuel pump. If not, the antisiphon valve will have a little ball in it.

Just to be sure. Does your engine look like this?

https://lh6.googleusercontent.com/-cJ51PTGaXCc/Sl3oTW2nnWI/AAAAAAAACXo/OGD10mW49AE/s948/GT40.jpg

ultrastryk
05-01-2012, 02:03 PM
Yep, that is my motor. I did pull those hoses and fittings to check the screen on the pickup tube. Any idea where to find one of those check valve fittings??

Thanks

east tx skier
05-01-2012, 02:26 PM
Try a Correct Craft dealer. As irony would have it, mine became gummed up again last week. I have two on order and may just start replacing it as a maintenance item. They're pretty cheap and easy to replace. I managed to work the little spring loaded valve around a bit and salvage most of the ski set, but the problem soon returned.

ultrastryk
05-01-2012, 05:01 PM
thanks much

ultrastryk
05-03-2012, 01:27 PM
I pulled both of those fittings off the top of my fuel tank, removed the brass barb from the 90 deg angle fitting, and there is no valve inside. I wonder if my anti siphon valve is somewhere else in the fuel line?