I run 30* all in timing. 177s, 9.5:1 compression w/ alum heads and 6psi. I have 2 - 3.0" original splined merc blower pulleys if anyone want to buy them.

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I'm interested in a 3.625 pulley if anyone has one.

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That is larger than a stock pulley and I don't think anyone ever made any that were larger.

My mistake, I was thinking the 177 & 250 pulleys were interchangeable. According to The Blower Shop the 250 is 16 rib & the 177 is 10 rib or keyed. That being said I have an old style (1.75” recessed) 16rib 2.75 for a 250 & need an old style 3.625 if anyone is interested or has one.

Convert over to the automotive keyed shaft and your pulley is a phone call to jegs or summit away. My opinion about what timing to run is this...My motor was run with retarded timing like around 30 total, and at about 140 hours (cant remember the exact meter reading) the exhaust valves were leaking badly. Retarded timing elevated the exhaust temps and ruined the valves. The Merc curve works very well and even though it has 35 deg total, its stepped and is not all in until 4500. Do not try to reinvent the wheel here.

177 was a weiand blower. 250 was a B&M. Different pulleys.

[QUOTE=Old Navy;3608633]Convert over to the automotive keyed shaft and your pulley is a phone call to jegs or summit away. My opinion about what timing to run is this...My motor was run with retarded timing like around 30 total, and at about 140 hours (cant remember the exact meter reading) the exhaust valves were leaking badly. Retarded timing elevated the exhaust temps and ruined the valves. The Merc curve works very well and even though it has 35 deg total, its stepped and is not all in until 4500. Do not try to reinvent the wheel here.[/QUOTE




How difficult is it to change to the keyed shafts?
Is it basicly a "bolt on" swap or does it involve disassembling the gear cases and rotors?

[QUOTE=JD33;3609129]
Pretty easy, no need to disassembling the gear casse or rotor, just disassemble the snout and swap the shaft to the keyed shaft. In case if you need to change the shaft coupler on the gear just disassemble the front cover.

Thats what it looked like from the pics I've found on the net, but sometimes looks can be deceiving. LOL

This may be the route I have to go, so far no stock dia. pulley with the correct offset located to fit my splined shafts.

[QUOTE=supermx96;3609138]Thats what I did. I think the new shaft came with a new coupler so I changed that too. Thats what you should do JD33 instead of messing with changing to my spined shafts/pulleys which may not work anyway.

I'm curious though if anyone knows what snout lengths merc used on thier 525sc? Its seems my splined blower pulleys are odd and never fit the merc splined shafts people have.