Merc 150hp heads on a 1995 200 hp?

[86vintage]

I was told that putting on the 150 hp heads would give you a higher compression on the 200 hp 2.5. Is it true that the chambers are less CC's and that they bolt on?
Thanks
James
86vintagehttp://forums.screamandfly.com/forums/images/icons/icon14.gif

[Capt.Insane-o]

No they are not fewer cc's if the 150 is a 2.5. Now swapping the tuner and carbs will definately be an improvement.

[86vintage]

The heads were from an earlier 2.0. I'll have to compare the heads tonight and CC them both. I was curious to see if any one else knows if the switch in heads works. I'll pull of the 2.5 and CC and compare squish and gasket alignment to see if what this dude from FLA said was the hot set up? Actually is?
Thanks,
James
86vintagehttp://forums.screamandfly.com/forums/images/icons/icon14.gif

[T-REX]

Tha later model (91 or later) 2.0, 150 iz a bolt on increase in compression...20-30#s...depending on tha shape of ya mota...

85-90 yeer heads are narrower than tha 2.5 block 2.0's, and sum people say they will not work, but I have used them(am use'in) and I have no problems...

[camaro7081]

try bolting it on the motor and do a compression check ! i tried a different set of heads on my motor to see if it will bring the compresion closer to were i wanted it i used the old head gasket checked the compresion and liked the new numbers and replaced the old gasket with a new one and the compression was perfect (this way you dont waste a bunch of head gaskets)

[86vintage]

Someone said don't do it because the earlier heads don't have dowel pins,
I feel the head bolts are good enough to keep the heads/gaskets located in the right place? What are your imput to dowel pins??

Two strokes have a performance advantage if the squish angles and deck heights are modified correctly - besides just cranking compression numbers. I want to run 150-160 psi with race fuel. Any tips in that area squish hieghts and combustion chamber angles and shapes??

The moto I am building is a 1999 200 hp EFI fishin motor that Jim Ruck is going to do it up with his magic and bore the throttle bodies larger with matching Butterfly plates. and I have a Bracato PCU, weld on Bobs offshore Exhaust and his nose cone, 2.4 tuner, will install Boysen reeds, and phenolic 1"spacer plate. The motor will have a nice fiberglass cowling with a Formula 1 style air scoop on the top to take advantage of "RAM AIR" - free Boost.
This motor is going to cracle at idle and sing at 7,000 rpm
Any tips will be apreciated!
James - 68vintagehttp://forums.screamandfly.com/forums/images/icons/icon14.gif

[T-REX]

What are your imput to dowel pins??



I've run'um both wayz...no problemz.......U want dowel pins, drill tha heads and use them......I juss figgered if'in tha hed bolts won't hold tha hed in tha rite place, U got more problemz to deel wit!!.......