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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10898
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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Inmar 350 in a 97 mastercraft.....has good poawer until full

Customer Question

inmar 350 in a 97 mastercraft.....has good poawer until full throttle...then doesn't get to historical top speed and will have slight hesitation....replaced fuel system 3 years ago including injectors....thought maybe it could be worn plugs or rotor maybe?
JA: Has the vehicle turned into a gas hog? And how does it start -- same as usual?
Customer: may use a little more gas than usuaal and have to pump it a few time before it starts
JA: What is the model of your '97 Chevy?
Customer: it is a 97 mastercraft boat 350 inmar engine
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: just replaced gas filter put some sea foam in the gas tank
JA: Anything else you want the mechanic to know before I connect you?
Customer: nope
Submitted: 11 months ago.
Category: Boat
Expert:  Tan replied 11 months ago.

Hello. My name is Tan.

Hesitation could be a fuel starvation issue. Have you tried running the engine off another fuel source?

If you have debris in the tank it can cause fuel starvation at full throttle. Putting Seafoam in the fuel tank just breaks old fuel up and can make matters worse. Where do you think the old fuel residue goes when it starts to break up in to chunks or small pieces? There is a screen on the end of the pick up tube that will clog with all this broken up debris which will cause a fuel restriction. The best way to rule out the boat side fuel system as a cause for your issue it to run the engine on a different fuel tank. You ask how do I do that. Get a gas about 3 feet of fuel hose. Fill the gas can up enough to go run the boat. Disconnect the fuel line coming from the fuel tank at the engine. Plug the fuel line. Now with the 3 feet of hose connect it to the engine then stick other end in the gas can secure gas can and run boat. Does the boat run better? If yes then we know the boat side fuel system is the problem. If no change we know the engine is the problem. So through the process of elimination we have ruled out the fuel supply.

Does this all make sense?

Customer: replied 11 months ago.
Yep thanks....
Expert:  Tan replied 11 months ago.

Your welcome........Please don't forget to positively rate my help as that is the only way I get credit for helping you.

Thank you......Tan

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