Weird electrical issues and no power at WOT

[HMcWhorter]

We have a 1992 Seaswirl with the 5.8L Cobra IO. We had a couple of things worked on earlier this year; 1. Due to water somehow getting into the gas tank, we had to have the carburetor overhauled (the accelerator pump was stuck) 2. Then we had it in the shop to try and trace a weird electrical issue, with the key on, but not running, activating the power trim would make the tach go crazy (the shop basically said that was not that uncommon and to just ignore it). They did identify a problem with the alternator only putting out around 12 volts so they replaced it.

So we take the boat out for a test run and when we put the throttle down the engine just coughs and sputters, backfires and will eventually just die. I pulled the spark arrestor and can see fuel flowing into the engine but it just won't run at other than idle. So we start limping back to the dock and noticed that activating the trim actually makes the engine run better, at anything over idle it sputters and backfires but by activating the trim, the RPMs go up and it runs better.

We're thinking there may be a couple of issues in play here but the fact that the power trim causes the tach to freak out when not running and then while running, makes the RPMs go up is just weird to us, do any of you have any thoughts on this issue?

Thanks in advance

 

[Scott Danforth]

you have at least one bad connection between the battery and the dash. clean all your electrical connections so they are shiny and clean enough your mother would eat off them

that means taking off battery cables and cleaning them
pulling harness connectors and cleaning them
undoing the ground buss bar connections and cleaning them.

 

[HMcWhorter]

you have at least one bad connection between the battery and the dash. clean all your electrical connections so they are shiny and clean enough your mother would eat off them

that means taking off battery cables and cleaning them
pulling harness connectors and cleaning them
undoing the ground buss bar connections and cleaning them.

Thanks Scott, we were hoping the shop (that specializes in electrical issues) would be able to locate the issue but they basically said: "Ignore it"... It's back at the shop now, maybe they will locate the electrical issue this time.

Any thoughts on the WOT no power issue?

 

[Scott Danforth]

Any thoughts on the WOT no power issue?

there is a whole sticky at the top of the forum full of links. one of those includes the most probable cause of low WOT

if you have to take your boat to a shop to get a mechanic at $125 per hour to perform tasks that my kids could do at age 10 (such as clean electrical connections), you will go broke owning a boat. it will take about 10 hours to go thru all the connections.

 

[HMcWhorter]

Well... Thank you for your opinion, I appreciate you taking the time to respond.