1991 175 Silverstar Eagle vs. 1991 175 Intruder & FastStrike

[skimmabird]

I'm almost done rebuilding a regular 91 175 60deg. It has the original block, original high compression heads, original carbs with a 72d high speed jet. It seems to me that a 91-92ish 60 deg 175 is the most powerful of all the carbed eagle motors. I don't see any part # differences between a regular 91 175 and a 91 175 FastStrike/Intruder other than the louvered cowling. Am I correct?

[Lockjaw]

I think it depends on the year. I have seen stuff in print that said the differences between a regular and a Fast strike were harder motor mounts, different carbs and port timing. I know on the 150 blocks, the fast strikes (GL block) don't have as high an exhaust port as the standard (EL blocks) 150. My 96 EL motor came with small bore carbs, but the motor mounts were quite stiff.

My current motor is an EL block 91 150, and the guy who did my machine work said he thought it was a 175 because there was no lip going from the liner to the ports on the exhaust side, which he said is usually a dead give away. I measured mine, its not a 175 though.

My original 96 motor ran really well. It had the bigger carbs, boyesen reeds on ficht reed cages and baker hot heads. I always felt my 91 and my 96 motor ran better with the high speed timing set at 18 degrees instead of 20 too. I am going to put 91 heads back on this motor one day, I have to come up with a good solution for my water pressure barb though, it doesn't have the same mounting holes as later model heads do.

Yours should run pretty good. I'd prop it to turn close to 6K light, and then hope it hits 5700 or so loaded. Mine runs around 5400 loaded and about 5600 light with a 24p Raker 2.

[skimmabird]

Thanks for the feedback. I don't see any difference in the 91 175 block part #s for a EX and GL. I know the 150's are a little different story but since all the 91's had the 195 head and the regular 175 uses the biggest carb and biggest jet it seemed to me by default a 91 175 is essentially a faststrike or intruder whether it is or isn't. At least from a powerhead output perspective.

[Lockjaw]

Well I would measure the exhaust port height on the 175 to be sure. If memory serves it should be 1.62 inches from the top of the port to the deck. I think the main diff between a 150 and a 175 is the port height on the exhaust ports.

I would check your plugs once you get it broken in and make sure you aren't to rich. I ran 72d's with my baker hot heads on a 150. But I also had ficht reed cages and boyesen reeds. And going up to 72's is what Baker recommended. I never really played around with it on my original powerhead.

On this one, I started with 73's, since I had Monty do the mod to the tuner and I blocked off the idle reliefs, and it ran pretty good, has pretty bad decal knock though. So I went up to 74's, and that is to rich, and didn't help with the decal knock, so I dropped back down to 72's.

I am going to put some 91 heads on it, I have 2 pairs, I just need to figure out the water pressure barb part. I think I can get down to a 70 or 69 maybe and make a little more power.

That and I need to order a set of 70's. I don't have any. I don't see many 175's down here. I know one guy who has one on a Javelin 389, but no idea what he runs like. One of these days I am going to chase down a block and build it, or have one ported. When I am rich and famous. HAHA

[skimmabird]

1.62 rings a bell. I saw that # on another thread somewhere and checked it. I mic'd it when I was checking the cylinder for wear & being out of round. I'm confident it is the original block, I have a good idea of its history.

[Lockjaw]

Shoot me a PM sometime when you get it broken in and let me know how it runs. I just don't ever see any 175's down here. I don't think I have ever run across one while out in my boat.

[skimmabird]

I'm curious myself, I'll let you know