2.5 crankshaft questions

[Jr in Jax]

Now that I have my Promax overhauled [runs very good], I am building up a spare powerhead and found the crank I was going to use had a spalled #6 journal.

Charlie has a good crank with the large main bearing so it would appear to be a 2.5 but we can not find a good part number on it. There are two part numbers for 2.5 cranks [maybe top/bottom guided?] The part number for my damaged [late model] crank comes up NLA. Does anyone have any ideas? I have talked to a guy in California that will repair my damaged crank for $500 plus shipping. Is this my best route?

Thanks for any help. I might not need a spare powerhead, but as many hours as I put on my rig, it would be "insurance".

 

[Dave Hensley]

Do you have the block you are going to use? The top bearing journal size and type of top bearing I think were the only differences in 2.5 cranks. Someone else that knows more chime in but I think fishing motor cranks stuck with roller bearing top bearings that were captured in a cage in the top bearing cap. HiPo motors went from that design to the ball bearing after 1995-1996?? Top guide or bottom guide depends on rod and piston combination.

 

[The Cashew Kid]

I'm pretty sure Dave is correct. I have a crank from an SST120 2 litre race motor in my promax. All promax motors had the small top bearing.

 

[Dave Hensley]

Jeff I think there was a 1-1/2" top journal and a 1-3/8" if my memory serves. It was just a matter of getting the right top cap and bearing. The bore in the block for the top cap was the same.

 

[The Cashew Kid]

Jeff I think there was a 1-1/2" top journal and a 1-3/8" if my memory serves. It was just a matter of getting the right top cap and bearing. The bore in the block for the top cap was the same.

Yessir. Far as I know you nailed it.

 

[Jr in Jax]

Thanks Guys, I appreciate the information. I will get Charlie to measure it.

 

[The Cashew Kid]

If you are talking about Cranshaft Specialist in California, they do outstanding work. I've seen some of it in person.

 

[Jr in Jax]

Jake called Charlie and told him that ya'll were right and it [Charlie's used crank] is the same crank that he has in his 2.5 so I will use it. I will keep my damaged crank as a just-in-case. I am not yet going to put pistons and rings into the spare, hopefully the Pro Marine 15-over pistons will still be available if I need my spare.
You guys are great!