Jet boat problems

[Patricklm82]

Hello everybody. I'm Pat. Kind of new to boating. Well jetboating anyways. I recently purchased a 1995 Sierra Viper with a Mercury Sport Jet 120 engine. It starts and runs. The fellow I bought it from told me that he could get it out on the water, run it for a bit, and it would die, but would start right back up and run fine after letting it sit for a few minutes. He also said it had only died less than 50% of the times he has it out last summer. He told me had had cleaned the carbs and stuff, but that he didn't know much about boats or the electronics on this particular boat. I have not started working on it yet, but have read what very limited information there is on it and found out that it could be the carbs, fuel pump, filters, or rev limiter possibly. As I am new to jetboats, I just wanted to see if anyone has any experience with this issue or might have any suggestions as to where I might start in order to diagnose and fix the problem. Thanks and have a nice day.

 

[jocolo21]

Not sure if it helps but. https://jetboaters.net/threads/1995-sierra-viper-question-s.24203/#post-405883

 

[Cobra Jet Steering LLC]

It is actually a 4 cylinder, 120 hp force outboard power head and there was all sorts of issues with those If you think it is the fuel system then totally clean the carbs fuel pump and fuel tank common issues are carbs fuel pump stator rectifier flywheel I know years back I posted a lot of info on the 90 and the 120 force engines so if you do a search you may find some of my posts they did away with those so parts may be difficult to locate. good luck with it .

 

[Cobra Jet Steering LLC]

I had a similar issue once and found small pieces of the fuel lines had become free floating inside the lines and they would block the flow of fuel to the carbs so if any trash of any type is inside the fuel talk or WATER in it this sort of thing will happen. When it is shut off the water or trash settles to the bottom of the tank and then it runs again until it gets sucked back in the pickup or in the lines.

 

[Patricklm82]

Still haven't started working on it yet, but I found out from the guy I got it from that he did put new fuel lines and filter on it, but that was all. He said it wouldn't actually due, it would cut out and lose power at higher rpms I'm not exactly sure what to believe but I'm pretty sure he didn't rebuild the fuel pump, and if he actually did clean the carbs, he probably didn't do something right. Either way, I'm going to go ahead and order the fuel pump rebuild kit and a new filter to start, clean the tank, and see where we go from there. Thanks again for the help.

 

[Patricklm82]

Still haven't started working on it yet, but I found out from the guy I got it from that he did put new fuel lines and filter on it, but that was all. He said it wouldn't actually due, it would cut out and lose power at higher rpms I'm not exactly sure what to believe but I'm pretty sure he didn't rebuild the fuel pump, and if he actually did clean the carbs, he probably didn't do something right. Either way, I'm going to go ahead and order the fuel pump rebuild kit and a new filter to start, clean the tank, and see where we go from there. Thanks again for the help.