merc rpm

bert · 14-04-2005, 05:30 PM

i have a 2.5lt merc when i bought it bloke wasn`t sure what it was all he new was it was a 2.5lt there is no serial no on core plug and saddle has been changed just had it rebuilt guy who did it reckons head is about 96 and carbs 93 200hp standard leg

what i really need to know is how far can i rev it

JamesM · 14-04-2005, 07:39 PM

If you want to rev to more than 6 grand you need to get rid of the oil injection as above 6K there's a good chance it may break and it would take the motor with it. To be honest its a good idea to get rid of it anyway and pre mix the oil and fuel.

Once you've done that you can rev it into the 6's but the heavy 40 amp stator will become the limiting factor. Change it for a 16 amp one of an older 2.4 or a race motor and you can rev to 7K. Thats about it though on the the standard cast pistons as they wont take much more than 7K for very long.

bert · 14-04-2005, 07:50 PM

been reving it past 6 but maybe the reason it blew up last time replaced pistons with wiseco 30+ will that make a difference

think i`ll have to up prop for now should have done these changes whilst doing rebuild can i just disconnect oil injection been told have to change other bits to

Gav · 14-04-2005, 08:02 PM

i would be interested to hear how oil inj is disconected too

JamesM · 14-04-2005, 08:20 PM

I think you just remove it and blank the holes off.

Wiseco forged pistons will take more than 7K but your 40 amp stator wont.

When you say 30+ do you mean they're oversized. Was the motor re-bored. Forged pistons require more piston to cylinder wall clearance than cast pistons due to the different heat expansion characteristics.

I'm not an engine builder or anything I just go looking on the Scream and Fly forum when people ask mercury engine related questions

JamesM · 14-04-2005, 08:23 PM

http://forums.screamandfly.com/forum...=oil+injection

bert · 14-04-2005, 11:24 PM

1 pot was already 30+ oversized and was intacted so rebored the other 5 to 30+ with all new pistons rings+ bearings but reving over 6k with 23" prop so probably try a 25" prop for this season if sluggish will change oil injection and stator cheers for your help + link

JamesM · 15-04-2005, 07:17 PM

Neil Holmes aka Phantom Evolution has loads of bits for sale. You could get a 16 amp stator and lightweight alloy flywheel of him. He may even have the bits you need to remove the oil injection.

http://www.boatmadforum.co.uk/showth...?threadid=2225

JamesM · 15-04-2005, 07:20 PM

You dont need the light weight allow flywheel to rev past 7K but it all helps to reduce the stress on your crank and bearings and as it would be apart anyway you may aswell fit one.

bert · 15-04-2005, 07:41 PM

not really fussed about reving up to 7k would just like to rev it as it is knowing that it is safe and not going to blow up more power is always good though going to try the 25" prop sunday see what i think but am probably going to take off oil injection anyway as this has caused most of my problems so far anyway

pm`d neil about stator but have not heard back yet