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Hard to start when warm. 357 mag bravo 4

G

GWELLS

New member
I bought my boat (1992 Trophy Cuddy) About 9 months ago. In that time I have burned out 2 coils, one from mercruiser and one from napa.* Th person that I bought the boat from said that he replaced the motor only a hundred hours before i bought the boat.* He said he replaced the motor with a 357 mag bravo 4. The motor in the boat has an Edelbrok carburetor and I thought that Mercruiser was putting Webber Carbs on these motors.* Now to my problem I seems that fuel is siphoning back into the fuel tank when i stop the motor, making it hard to start.* I installed a primer bulb and it seems to help, I can't find any leaks along the fuel line. So air must be getting in from the carb.* should this be Happening?
Aloha, And thank you for any help you can give.
 
First off get rid of the squeeze bulb.......may not allow enough fuel..


Yes Merc used webber.......pretty much the same as a carter.......

All 350 mags had the oil filter mounted remotely on the right side maniffold/elbow. Is this there? if not then NO 350 mag..............it may be equal in power to a mag with the carb and intake upgrade in output but it is not an original oem 350 mag.

Is this a mechanical fuel pump or electric?

Is the original steel fuel line in place or has it all been changed to hose??

At the gas tank where the fuel supply connects there should be a spring loaded chack valve (anti syphen).

is that pressent. they are typically aluminium NOT brass.

Also it is very unlikely the fuel is syphening back to the tank. If it is then maybe your gas tank vent line is clogged. there would have to be a vacuum on the fuel system to get the gas out of the carb once in the bowl

If gas is absolutley "syphening" it may be going into the motor and not back into the tank........ after a shut down and you remove the flame arrestor if you activate the throttle you should see gas bieng squirted into the intake from the accelerator curcit. If not then the bowl is possibly empty.

Also no bavo 4......only I II III.

a 350 mag vs a 350 normal is no more than a slightly recalibrated rochester carb, (a very slightly higher/longer plane intake manifold posible but i dont remember right now) and a 3 or 4 inch tall flame arrestor. NO other internal parts were changed between regular and magnum.
It raised the hp rating from 260hp standard to 270 ish hp rating.......... so only 10 hp..........
 
I have burned out 2 coils,
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Are you getting the correct coil? Verify the coil ground is good and that it is getting a full 12 VDC. Verify the 12 volt wire is not corroded internally...replace it if it is hard or the insulation is cracked or burned.
 
If you are running the mercruiser thunderbolt IV or V ignition then you need a coil with a internal resistor.

A point ignition uses a coil wirth a external resistor (ballast) or resistor wire (gm style and mercruiser)

If you do not have a mercruiser ignition then you need to identify what you have.


The thunderbolt ignition is one of a kind and has a unique cap.

see below

http://www.boatingsolutions.com/images/18-5395.jpg
 
GWELLS said:
That's one of the things I'm trying to determine, If it has a Edelbrock carb is it really a 357 mag bravo 4v. how do I figure out what coil it needs?
Thank you for your help.
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Could you try posting some photos of the engine and distributor/coil area it may help us help you. Also do you have the engine serial number by chance?
 
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