New Boater Need Help!!!

i just bought a 1985 mark twain boat. dont no much about them other then the fact that i wanted a boat. well it ran fine when we got it he also said it sticks after about a half hour to a hour drive, its a mercury 2 stroke 150hp engine we took it out yesterday for a test drive. it did fine, for a while then cut down to 3000rpms like he said, well then after about a hour of riding around it just cut out, i was thinking the problem may of started with the carbs, but my buddys dad thinks its a fuel line. Now that could be true to y it shut off but i dont think that would be the reason it keeps at 3000rpms. also the guy said it had only been a freshwater ran boat and we run salt water? can anyone help or shed some light on this situation????

Re: New Boater Need Help!!!

Is that motor an inline six or V6? Post the serial number, and we can figure out the year. Sometimes the RPM limit is fuel related, sometimes it is Ign related

Re: New Boater Need Help!!!

ok i got the serial number it is 4125102

Re: New Boater Need Help!!!

Ok, that shows as as a 1975 Merc inline six. Is that correct?

Best thing to do is start at the beginning. Take a compression test. Should all be 110+PSI and even. Next put a timing light on all cylinders and run motor on flush device. You should see consistant spark on all six. Watch for spark arcing on wires. Especially on lower cylinders. Replace any wires that are bad. They unscrew from the distributor cap. It does have a distributor, right?

The behavior you describe is unusual. Normally distributor ign motors either work or don't. They do not usually lose some cylinders.

Post back with updated results.

Re: New Boater Need Help!!!

well i have a buddys dad that is working on it, he thinks its the carborators and the fuel line

Re: New Boater Need Help!!!

n00boater89 said:

well i have a buddys dad that is working on it, he thinks its the carborators and the fuel line

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Buddys dads are great people, sometimes they need a little help from folks who have already made all the mistakes. Keep posting what you find or suggest that BD check out I boats Merc Forums for free support.