Full Power, Finally !

[Rick_Powers]

(This is the third and final thread in the long saga that started as "Fuel Starvation, Arg!", then morphed into "Vacuum Test Guage Results".

My engine finally delivers full power at full throttle!

The boat is a Catalina 27 and I can maintain 6.8 mph at full throttle for hours on end.

What was the final culprit?

Dunno. It just started working great yesterday.


However, I have some possible hypotheses:

1) The squirrel in my exhaust tube left, clearing a blocked exhaust.

2) The mass amount of mental force exerted my the MMI community caused a mass transfer of energy that overcame some Heisenburg uncertanty principle phenomenon.

3) My threat of having to rebuild the carburator caused the problem to clear up. Engines know threats when they hear them...

4) Some small particle in the carb float valve got dislodged (most likely).


Now, I have a new tachometer installed, and here are my measurements. Please tell me if they sound reasonable, as I do not know what is normal (the readings seem a bit low).

Idle = 200 rpm

Full throttle, neutral gear, winding out at 3000 rpm (Painful sound...)

Mid throttle, forward gear (load) = 1000 rpm (5.6 mph)

Full throttle, forward gear (load) = 1500 rpm (6.8 mph)


The basic good news is that I can crank out full hull speed all day long now (anybody want to go water-skiing on the San Francisco Bay?)

Lessons learned include:

1) Use this forum for great advice (thanks to all !)

2) Know your fuel system from the condition of the inside tank walls, to the freshness of your gasoline, to all the fuel line connections, filters, etc., all the way to the pump(s) and carb.

3) Be prepared to rebuild your carb, but if you can avoid it, that's great too.

4) I now have two (different) fuel pumps in line, both downstream from the Racor fuel filter. Somehow, that seems like a good redundancy.

5) Don Moyers deserves a hero's thank you for all the thoughtful attention to one guy's misery. And thanks for the beta-version vacuum guage kit.

I hope that all the discussion over this vexing problem will be a help to others in the future.

Until the next problem arises, I remain,

-Rick Powers, Palo Alto, CA

(PS- Photo is of Belize)

[roadnsky]

Tach settings?

Rick-
Not to extend your "string" too much more but...

RPM's seem a bit low. Especially at idle.
Normally it'd be 700 - 800.
Under load seems like it should be a bit higher too. Closer to 1700 - 2100.
(Speeds are right though)
Since you're not stalling at idle and you're reaching hull speed, I'd say it's not a big deal. Likely a un-cal'd tach?
I'll leave it at that unless you wanna get into tach discussion...

(Sorry to rain on your obvious sunshine!)

[roadnsky]

One last note...
On another thread, someone mentioned they're tach was set for 6 cyl's instead of for 4 and they got false RPM readings.
Could you have something like that on your tach?
-Jerry

[Rick_Powers]

Tach

I too am concerned about the tach reading being off.

It is set to 4 cylinder. I will double check other settings to be sure.

I had expected idle to read ~800 and full power w/ load to be closer to 2000.

I suspect I have a bad guage. Will return it and try another.

Thanks guys!

[Baltimore Sailor]

The tach set for 6-cylinder was mine, and my numbers are right where they should be now that I've set it properly.

I wonder what the result would be if the sensor lead for the tach was on the positive terminal of the coil instead of the negative? Would it blow the tach/coil/entire ignition system, or would you just get strange readings?

[roadnsky]

Rick-
Actually, looking at your numbers again, it looks like they are each about 500 RPM low across the board. Hmmmm...

[Rick_Powers]

Tachometer

Yes, they do look 500 rpm low across the board.

I went back down to the boat today and tried all possible settings, and the current 4-cylinder setting gave the highest (as reported above) numbers.

The send is wired to the coil negative terminal.

I'll talk to the vendor and see what they say.

[sastanley]

Rick, I amusing a $25 Sunpro tach from the local Autozone. It could be a double-check, and if you don't screw it up, you could return it after tests.

[67c&ccorv]

I'd say it was the "squirrel" Rick!

[David Masury]

Not to throw water on your sunny day, but isn't 6.8 knots faster than hull speed. My 27 foot boat has a water line length of 21.4 inches and a hull speed of 6.2 knots. 6.8 knots is what a water line of 27 feet should create.

1.34 x the square root of the water line equals hull speed.

But while I make fun of your boat speed, congradulations on having a well running Atomic Four

David

[Rick_Powers]

Hull Speed

Hi David,

I'm no marine engineer, but using my Garmin GPS I measured speed (actually GPS MPH) going in one direction then back the other direction.

My boat will slightly raise up (plane?) when I crank it.

Again, anybody want to go waterskiing on the SF Bay?

-Rick

[MikeB.330]

6.8 mph = 5.9-6.0 knots

[Mark S]

Rick,

"Raising up" means reaching hull speed which means more gas is only more gas and not more speed.

My idle is around 600-800 rpm and I generally cruise under power at 1800 rpm which is 5 knots absent a head wind or current. More than 1800 rpm gives me more speed but begins to be more fuel consumptive, so I only exceed 1800 rpm when special circumstances require it.

Congratulations on your problem solving itself. Sometimes we do our best work when we do nothing!

Mark

[Rick_Powers]

The tachometer WAS bad !

So I took Shawn's advice, and went into the local auto parts store, and bought a $29 tach.

Wired it to the boat, and immediately measured:

Idle 800 rpm

Load 2000 rpm

Max rev 3200 rpm

Another problem solved! Time to return the faulty guage to West Marine.

I think I'll stay with the cheaper auto tack. What a great idea!

PS- I appears to have a sealed housing (front and back) so I would guess it will survive a marine environment.

[roadnsky]

Great! Congrats!
Sailing time...