Alpha One speedo isnt working

[Captianloud]

3 questions <br />Speedo, carburation, prop <br />I put narative with pictures here:<br /><br /> http://users.adelphia.net/~chrisradvanyi/speedo.htm <br /><br />I tried to keep it as small as possible.

 

[JoJoBetsy]

Re: Alpha One speedo isnt working

I don't think those holes are for the speedo. I thought that the small hole on the leading edge of the lower unit was for the speedo and it does quite often get clogged with debri. You can see it well in the second pic you've provided about 1/2" up the leading edge of the drive. <br /><br />Check me though, I'm just a cadet. I'm sure an Admiral will be by shortly.<br /><br />jb

 

[Don S]

Re: Alpha One speedo isnt working

You shouldn't have blown air into the drive, You may want to seperate the upper and lower gear housings and check the plastic housing for the shift and speedo. May have blown the seals out of it.<br /><br />Note hole ( a ) in the picture below.<br /><br />

 

[JoJoBetsy]

Re: Alpha One speedo isnt working

Wow, didn't I say shortly. Thankfully I wasn't wrong. ;-)

 

[Captianloud]

Re: Alpha One speedo isnt working

Thanks Don, Sweet. I'll have to check that. Im not the type to hold the air gun wide open into an unknown oriface. IF my breath could move the speedo needle, I was afraid I would damage the gauge with too much pressure, I was carefull. Beside so much escaped from where I highlighted the arrows It never got a chance to biuld any pressure. I think the seals will be just fine.

 

[Bondo]

Re: Alpha One speedo isnt working

I am guessing this is the inlet for the gauge. There is one on each side.

That's your mistake,.......<br />The Pitot Tube is in the Very Point of the Lowerunit Leading Edge..............<br />

Is there a formula to verify gauge accuracy? for example 10psi hose pressure = 25mph as indicated by speedo gauge ?

Probably would be a "As Per Manufacturer" kinda thing,......<br />In reality,...... No.... <br />There's a couple of Good Speedo threads going on in the Boats forum now......<br />

4.3 L V6 w/ Weber 4 barrel. I have the slow circuit mixture screws set at 1 3/4 turns out. Anybody with this setup know where about they should be?

All the Answers to your Carb Questions are Here.................... <br />

Right now I have the 1.81:1 ratio Alpha 1 Gen II sterndrive. I am turning a Michigan Wheel, Aluminum, 3 blade prop, 14.25 X 21. I can easily run the V6 right into the red (+4500RPM) if I want too but dont because she still isnt broke in and you just dont do that to engines.

I Think a 4.3l would normally have a 1.65/1...... A 23" Prop might be Too Small........<br />Your engines Redline should be 4800rpms,...... I see No Problem with short Bursts to 5000rpms,.... <br />It Won't bother it At All,..... <br />Mine will just pull 4850/4900rpms.......<br /><br />After Break-in of course.........

 

[Captianloud]

Re: Alpha One speedo isnt working

Thanks Bondo, <br />The hole in the lower unit has to be clogged. Yep, you're right I checked the wrong hole.<br />Thanks for the carb info. <br />Its the 1.84:1 for sure. outdrive serial OKO7O284. The US marine tach gauge goes red at 4500, the cam I put in can handle 5500, so youre right I see no prob with flirting with 5000, in short bursts. But when I hit 4400 just for a brief momment, I still have a lot of lever left. You think a 23 might be too "tall" or still not enough?

 

[Don S]

Re: Alpha One speedo isnt working

I have the slow circuit mixture screws set at 1 3/4 turns out. Anybody with this setup know where about they should be?

You sound like a parts installer, not a mechanic. The number of turns is nothing more than a starting point for the final adjustment. Every engine is different, so giving how many turns each screw is turned out is just a waste of time. What works for one, won't for another. Besides, you have something other than marine there..... Right????<br /><br />Now if you have a tach, and a vacuum gauge you could adjust it properly. After the timing was set correctly and you was sure of the proper advance timing. Don't want no holes in pistons now do we?<br /><br />Regarding your prop, going to a 23 pitch will slow down you WOT rpm, but it will also kill the effeciency. Going over 21 will work, just not the best. Your best bet would be to increase the diameter. After you determine that your tach is actually correct and what your actual WOT rpm is.<br />Like Bondo stated. Short trips to WOT on a new engine doesn't hurt it at all.

 

[Captianloud]

Re: Alpha One speedo isnt working

Thanks for the shot Don, you're right all engines are different. Most carburators have a standard setting. Thats what I was looking for. The starting point. <br /><br />Whats the max prop dia with the Alpha 1, my trim tab is just a flat anode.

 

[Don S]

Re: Alpha One speedo isnt working

The Alpha I Gen II drives will handle up to 16" props in some designs, the 14 1/4 is on the small side of the range.<br /><br /> http://www.mercurypartsexpress.com/...&chart=411&key=9895&level=3&store=Accessories

 

[Bondo]

Re: Alpha One speedo isnt working

Ayuh,...... All of the Alpha series of drives have 8+" from the center of the propshaft, to the Cav. Plate,.......<br />They Will swing 16"s of prop Diameter......<br />BIG Diameters Usually are found on the Lower Pitched props.....<br /><br />For Pitch,.... Standard production props run from 15" to 23",... Some manufacturers also build 25" aluminum props......<br />After That,.... You're looking at Custom SSteel props up to about 30".......<br />

You think a 23 might be too "tall" or still not enough?

Only You can figure that out,... With a Good Tach,+ the boat Loaded in a Normal fashion........<br /><br />I'd be shooting for a WOT of 4800/5000rpms.....