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FasTech 292 w/350s Max RPM / Speed.

Old 05-28-2021, 12:14 PM
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Default FasTech 292 w/350s Max RPM / Speed.

I put 2 new 'base' (short blocks) into my 292. (Mitchigan Motorz)

What are others, with 350s seeing as WOT for RPM? Just want to make sure I'm close to spec. I planned to take the props to Black Dog Props in MD this winter as they are now 20 years old, just to go over, and refresh.

Merc Manual says WOT is 4400-4800

I'm seeing about 4600 on mine, so it looks like I'm dead center within spec.
I can usually just break 62-63 MPH with 2 people and half tank or so.

We usually cruise around 42mph (lowest speed I can stay on plane). (best MPG).

I'm not looking to add any MPH/RPM, just verify I'm in the ballpark. I thought 2 'new' engines might buy me something over the old ones, but it sure doesn't look like it did.

The old engines: Strb was no start (turned out to be a fuel pump). and oil came out like a milkshake. and zero compression across multiple cylinders.
Port: also hard to start, and zero compression across multiple cylinders.

The engines failed at approx 19 years, ORIGINAL exhaust manifolds and elbows, which I think doomed the engines. Rust all over the insides of the engines once I took the heads off.

New engines run great, with all new exhaust and elbows...
Just thought I'd gain a bit more than I did over engines with no compression across multiples plus blown head gaskets lol. I guess you can run these engines into dust and they don't lose that much HP lol.
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Old 05-31-2021, 11:33 AM
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I have 26P bravo 1 props and I'm seeing 67-68 gps at 5000-5100 rpm. I usually cruise 60 mph at 4400-4500.
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Old 05-31-2021, 07:31 PM
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The boats on the lift for summer, I'll have to check the props this fall. Something about a 28P comes to mind, but I don't want to state if not 100% sure. Maybe next time I take it out and go for a swim I can put the drives up and take a look. I should note that in my boat excel sheet. I cruise around 37-3800 RPM at 42 mph to save fuel. I'll take some RPM vs MPH when I hit 1/2 tank if I remember next time. Speedo is GPS.
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Old 06-06-2021, 07:47 PM
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2001 350s, 1/2 tank
RPM3600 - 42 MPH
3800 - 44
4000 - 50
4400 - 56
4800 - 62 WOT

48-831915 28P props



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Old 06-07-2021, 11:24 AM
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So you're aware, the WOT range you call out in your original post is recommended for the inboard models in manual 31.
The sterndrive below in the snip.
So if you're wanting to wring it out and you have 28 pitch, maybe step down to 26 and try to get it up to 5000.


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Old 06-07-2021, 03:24 PM
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Thanks for the info. If it's 5,000 RPM, and I'm at 4800 now... I'm not sure I'm ready to invest the cost/time to go to a 26. I'm not sure I'd gain anything?
Yes, I'm fairly certain the RPM would go up, but without testing, would the MPH?

Frank seems to have me on MPH though, that's for sure.... hmmm... Is it really just the lower prop?

From RPM and MPH I should be able to calculate slip as well?
Take off is adequate now, if I go to a 26, I assume it would pop up faster, but if I'm running higher RPMS, I wonder what the impact on MPG will end up being.

At 42 MPH I can usually pull off almost 2 MPG or so.

Is there a 27 pitch? Of course, at $450? each... I don't think I'm dropping that to change this up... I don't think I'd ever recover the cost in fuel or smiles adding a hair more MPH...

Okay, looks like it is what it is, and it's running well. Gonna leave it alone for now.

thanks everyone!
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