Thanks for all those who posted suggestions to my last post a couple of days ago.
Took the boat back out, and it ran for about 20 mins at WOT (sitting on 4500rpm). It then died back down to 3000rpm.
I did a quick idle mixture adjustment, as best as i could while trying not got get run over by other boats, and that seemed to make a huge difference to low end performance. It would die out after about 10 secs at WOT, but would run below say 3500rpm all day long. Opened it back up to WOT and noticed that if i pumped the primer bulb, it would pick back up to WOT immediately. It took a bit of managing to get this right. If pumped too much, the engine would die immediately, and sounded like it was flooding. If pumped every 3 secs or so, it would stay around the WOT RPM mark. After replacing most of the fuel line components, I'm pretty sure its the fuel pump.
Off to the local marine dealer to get some new plugs ($9.50 each) and a rebuild kit for the pump ($60). Have ordered a rebuild kit for the carbs, which was quoted just under $100. I'm sure if Mercury o/boards were made in Australia, parts would be alot cheaper!
Do you think its worthwhile to pull the carbs and clean them out? In the Seloc Manual, they call out sizes in the main jets according to whether the engine is above or below a certain serial number. From what i can see, Pre 79 or 80 model 115hp inline 6's had a slightly smaller main jet and a slightly bigger idle jet. Post 79 or 80 model 115hp inline 6's had a slightly larger main and slightly smaller idle jet. I cannot see any difference between the two engine setups (eg carbs). Does anyone know why a larger main jet was used for the same engine setup? Has anyone dropped a size on the main jet with favourable results?
Took the boat back out, and it ran for about 20 mins at WOT (sitting on 4500rpm). It then died back down to 3000rpm.
I did a quick idle mixture adjustment, as best as i could while trying not got get run over by other boats, and that seemed to make a huge difference to low end performance. It would die out after about 10 secs at WOT, but would run below say 3500rpm all day long. Opened it back up to WOT and noticed that if i pumped the primer bulb, it would pick back up to WOT immediately. It took a bit of managing to get this right. If pumped too much, the engine would die immediately, and sounded like it was flooding. If pumped every 3 secs or so, it would stay around the WOT RPM mark. After replacing most of the fuel line components, I'm pretty sure its the fuel pump.
Off to the local marine dealer to get some new plugs ($9.50 each) and a rebuild kit for the pump ($60). Have ordered a rebuild kit for the carbs, which was quoted just under $100. I'm sure if Mercury o/boards were made in Australia, parts would be alot cheaper!
Do you think its worthwhile to pull the carbs and clean them out? In the Seloc Manual, they call out sizes in the main jets according to whether the engine is above or below a certain serial number. From what i can see, Pre 79 or 80 model 115hp inline 6's had a slightly smaller main jet and a slightly bigger idle jet. Post 79 or 80 model 115hp inline 6's had a slightly larger main and slightly smaller idle jet. I cannot see any difference between the two engine setups (eg carbs). Does anyone know why a larger main jet was used for the same engine setup? Has anyone dropped a size on the main jet with favourable results?