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-   -   engine acting wierd at full throttle (http://www.mariahownersclub.com/forum/mercury-mercruiser/1204-engine-acting-wierd-full-throttle.html)

MariahMX20 05-30-2008 05:31 PM

engine acting wierd at full throttle
 
my drive is a omc cobra but no one looks at that section so i am going to post it here since it could be a similar issue to a merc drive. i have a ford 302 h.o. motor and when i am at full throttle sometimes it will just kinda die out and drop down from around 4000 rpm down to like 2500 and i loose all speed. everything i have checked seems fine and if i stop, turn her off and then start it again it will be fine. my two theorys right now are 1 the fuel pump is starting to fail or 2 the shift module is kicking on when it should not which would screw up the timing and i am really starting to think that is the issue at this point since i know the linkage is not adjusted perfectly yet . any other ideas? i want to mess around with it this weekend but we just got dumped on with rain and the river is a loggy mess. hopefully sunday maybe.

Captain Steve 07-03-2008 01:52 AM

I hope you have solved your problem already. From your description you might be getting vapor lock in your fuel delivery system. I have never had it, but seems to me that heat could cause fuel to vaporize and interrupt the considerable flow your 302 demands at WOT.

Regards,

mikeyt 07-03-2008 02:51 AM

I think its cuz you have a Ford motor...... :)

WetWilly 07-03-2008 08:14 AM

Hi MariahMX20,

Do you have electronic ignition on your motor? I have seen this on several cars before and it was due the ignition modules.

Doubt it's the fuel pump, typically turning the motor off then right back on won't cure a pump issue. Have you changed you fuel filter lately?

I would think if the shift module was kicking in, it wouldn't do anything to your motor. Shifter modules typically prevent motor start unless the shifter is in neutral, like a simple starter kill switch.

Good luck and let us know what you find,
WetWilly

MariahMX20 07-03-2008 12:09 PM

the ignition is a prestolite ditributor that is fully electronic and has had everything replaced inside. fuel pump is mechanical so turning it off then back on would not cure it, the diaphram may need to be replaced. i have had the boat out twice with no shift module hooked up and have had no issues. on a omc cobra which is the drive i have, the shift module assists in shifting, it porpusly messes with the timing on the distributor so that the engine drops in rpm while shifting therefore the gears can lock in at a lower rotation speed making super smooth shifts. so far i am guessing ita a misadjusted shift switch, the actual switch that controls the module. thanks for the help!

MariahMX20 07-03-2008 12:18 PM

Quote:

Originally Posted by mikeyt (Post 8395)
I think its cuz you have a Ford motor...... :)

you know, i hated the ford engine when i got it, i am a chevy guy and build small blocks for my project cars all the time, i know a ton about chevys. i always use to talk about swapping the drive and engine over to a 350 chevy and bravo 1 but i have to tell you, i have fallen in love with this engine and drive combo, it is a great setup! only downfall is that parts in town are unheard of so i have to order everything online which is fine because i do all of my own work on my boat. of all of my boat problems not a single one has related to the motor itself. i also have added side exit corsa exhaust on this boat and you can ask anyone in my marina, they know my boat is coming whether coming up river or just pulling into the marina, kinda of like a mustang, it has a distinct sound and even a chevy guy will admit that a mustangs always have a nice sound to them. i guess i have to say is you shouldnt talk down on something like a ford motor until you have owned a boat with one.....:wink_thumbup:

mikeyt 07-03-2008 02:00 PM

i wuz kiddin'. ;)

dieselwiezil 07-16-2008 05:00 AM

have you changed your fuel filter? There is one up on your carb too.

MariahMX20 07-16-2008 12:10 PM

i have not been in my boat too much since we have went from flooding to drought here in omaha, that and we have been boat pooloing using my buddies baja so i have not confirmed yet but i am pretty sure the misadjusted shift module is the issue. i unhooked it and have taken it out twice since then with no issues, now if i can just get the time to go down and get it adjusted i will be set!


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