Test Run

[Boatboy88]

Finally got out to run my Vintage A Class Hydro with a KG4-H. Topped out at 38.2 with no air traps and I have not experimented with props yet. Any tips of pitch? Hope I can get her out again soon! I would post the video however the file size is too big.
Dan Scheda
Brockport NY

[ZUL8TR]

setup

That is not a bad speed but a low speed for a A hydro with KG4H. When I ran A hydro on a B,C Wetback (to big a boat but wanted course time as 1st year starter) I ran one of Marshall Eldridge Jr engines that we just threw on the boat and guessed at the setup and I ran very close with the lead boats. Had some good starts and it took to lap 3 to catch me. Speed was in the low 50's I believe. I was over weight by 25Lbs min because I was primarily running 25ss at 355Lbs min and ASH was 330 Lbs min.

Tell us about these:

What is boat make and year?

Length of afterplane (rear of sponson plane surface edge to rear plan surface edge?

Weight of hull, and total weight with you at running setup?

Vertical transom rear height to bottom plane?

As a start need to run that engine with prop shaft rear center no deeper than 1" below bottom with shaft level with bottom.

Can't tell you about the traps unless we know if the hull is floating at speed, but based on what was running in A hydro when I was racing there was use of full traps and engine height as high as possible for water conditions. There was no height rule back then. Some guys ran the prop shaft center at the bottom.

What is condition of engine, compression, etc?

What piston depth BTDC do you have the timing set? Did you do it with a dial indicater and buzz box or other? Need a dial indicater and buzz box to do it right.

What is the prop you are using? Do you know the engine rpm's. Marshall supplied me props to use with his engine so I do not know diameter and pitch. Perhaps others will chime in on this point?

[Boatboy88]

As far as the make I am pretty sure it is a Glen-L Tiny Titan. I bought it from a guy who built it back in the late 50's early 60's.
The running weight of the craft is about 310 pounds. I've never weighed the boat by itself but I guessed it weighs about 70 pounds.
I have the transom height set at 15 3/8 inches and it just barely gets on plane.
The measurement from the rear of the sponson to the rear of the boat is 47 inches. I don't know if that's the measurement you were looking for.
The compression on the motor is 120 on top and 118 on the bottom.
I have the points set at 20 or 22 thousandths at top dead center but I don't remember.
As for the prop I know practically nothing about it. It came with the motor when we bought it. I will go measure it later.

[Boatboy88]

Here is a video of the test run. Watch in HD or else you won't be able to see anything.
http://www.youtube.com/watch?v=Yo36o...ature=youtu.be

[ZUL8TR]

the ride

The video indicates that the boat is riding nose heavy because of the excessive water spray off the front sponsons. The sponsons need to off the water for less drag and good speed. From the sound of the engine I would estimate that the rpms are less than 6000 to low for good speed.

Setting the ignition just by gapping the points is not adaquate, you need a dial indicator and buzz box. If not you need a way to measure the piston firing at exactly 180 degrees apart to synchronize them. Then you need a way to measure at what advance the points fire.

Let us know what you measure for diameter and pitch (if you can) on the prop. Post a pic of it.

Running weight not bad.

The transom height at 15-3/8 is low, I would be in the 16" range for the quicki you are running. The higher you go the more pitch you can run to take advantage of the air entrained water and less drag on the motor lower unit.

[3autility]

Kg4h

My KG4Q runs about 44 on a 1985 Giles hydro. I think based on the video, that as others have said, you need to kick out the motor more and raise it on the transom. Air traps would help, but you may not be able to get more speed out of the boat, which is an older design. In any case it is always a fun ride. Were you running on the Barge Canal? I will be at Honeoye Lake after the 4th for a week with the hydro and a runabout and some old Mercs.

[Boatboy88]

Thanks for all the great information! The first thing I'll do is get the ignition timing correct. What is the max spark advance I should run? I'm using 93 octane and TCW3 oil.
Thanks again!

[ZUL8TR]

ignition and fuel

Thanks for all the great information! The first thing I'll do is get the ignition timing correct. What is the max spark advance I should run? I'm using 93 octane and TCW3 oil.
Thanks again!

Dump the 93 octane these engines run better on 87 fuel (only use non E fuel). I never ran anything but 87 when I was in competition in 25ssh and 20ssh and it performed the best. I used Merc Quicksilver oil at 20:1. What brand oil and ratio are you using?

Each engine, fuel, prop and how you want to drive it will have different timing settings. As for the timing a safe start would be 0.275" BTDC then test and try different settings and note the speed. The old mags that are used on these 2 cyl engines that I am familiar with were set at a 0.018" point gap (the later Phelon mags after 1962 used 0.020"). Note when these mags are setup one point will be at 0.018 (or 0.020) and the other will generally be slightly different when set up with a dial indicator and a buzz box. The goal is to get the points to fire at 180 degrees apart at the same BTDC position for each piston. The FSM notes the use of a degree plate and a buzz box of sorts to do the synchronizing. If these tools are not available set both points the same (by feel) but you still need to set the desired piston BTDC position with a gage to determine where the mag needs to be locked down to.

[Boatboy88]

Thanks for all the help! Measured the prop tonight. Here are the particulars:

Diameter: 5.6"

Pitch @ 3" dia: 7.78"
Pitch @ 4" dia: 8.38"
Pitch @ 5" dia: 9.25"

It has a smallish cup, and "Marchetti" engraved on the hub. It's either highly polished stainless, or chromed. As I studied it carefully, I realized it seems to be quite a beautiful piece of work (photo attached).

Given the measurements I made, is there a conventional way of describing the pitch? ie, would one call this an 8" pitch? or something else...

I am also considering how to tach the engine at speed. Any tips? I measured the (audio) pitch from the video - it's a G# when passing directly in front. That's about 208 Hz, or 6200 RPM. Of course that assumes my video faithfully reproduces the sound, which it probably does. 6200 RPM at 8" pitch and zero slip gives 47 mph. My 38 mph says I'm operating with about 20% slip, which seems reasonable. All those numbers hang together, FWIW.

I looked at the video again carefully - I definitely think the engine needs to be tilted out more to get the propshaft level.

Thanks all. Looking forward to cracking the 40 mph mark with some additional fine-tuning!

[ZUL8TR]

measurements

Thanks for all the help! Measured the prop tonight. Here are the particulars:

Diameter: 5.6"

Pitch @ 3" dia: 7.78"
Pitch @ 4" dia: 8.38"
Pitch @ 5" dia: 9.25"

It has a smallish cup, and "Marchetti" engraved on the hub. It's either highly polished stainless, or chromed. As I studied it carefully, I realized it seems to be quite a beautiful piece of work (photo attached).

Given the measurements I made, is there a conventional way of describing the pitch? ie, would one call this an 8" pitch? or something else...

I am also considering how to tach the engine at speed. Any tips? I measured the (audio) pitch from the video - it's a G# when passing directly in front. That's about 208 Hz, or 6200 RPM. Of course that assumes my video faithfully reproduces the sound, which it probably does. 6200 RPM at 8" pitch and zero slip gives 47 mph. My 38 mph says I'm operating with about 20% slip, which seems reasonable. All those numbers hang together, FWIW.

I looked at the video again carefully - I definitely think the engine needs to be tilted out more to get the propshaft level.

Thanks all. Looking forward to cracking the 40 mph mark with some additional fine-tuning!

Something strange here with the prop pitch numbers. Blade angle (see sketch) should reduce as the radial distance increases from the center thus pitch should not increase at radius increases. Not sure how you measured the pitch numbers but here is the formula for converting to pitch from blade angle:

Pitch (inches) = 2 x pi x radius x tan (blade angle)

pi = 3.14....
radius = distance from center to point on the blade in inches
tan = tangent of the blade angle
blade angle = angle measured from 90 degrees to the blade surface to the prop shaft centerline.

See attached sketch

Note that at a given radius the pitch is variable increasing from the leading edge to trailing edge. So to be consistent you can measure blade angle at the center of the blade at a given radius then use formula for pitch. Pitch sometimes taken at the 70% radius at the center of blade, other times it is averaged of several measurements.

Kick out engine to get the prop shaft level to bottom note ride then kick out more and test. Prop shaft height also needs to be adjusted as well. take videos so we can look at ride and discuss: Have fun

[modracer7b]

The prop looks about right for the old mercury. I believe I used to set the points at .018 for the first and 180 degrees later for the second point opening. I ran timing at 375 to 425 for runabout and 425 to 450 for hydro. Some engines could run higher timing than others. A safe timing would be about 375 for a laker rig such as yours. In the sixties, a winning runabout ran 48 to 52 and a winning hydro ran 55 to 58. The OMC J props are the size that fit the old A. Many OMC J rigs were running old Merc A props.
From 63 to 69 our team took 7 National High points and 3 National Championships with 2 John & Flora Blank Awards (highest single class point total in stock outboard) and a few top 5 national finishes and a few northeast divisional championships.
The prop you have would have come from Nick and Tony Marchetti of Marchetti hydros which we ran for a few years, so if has not been damaged or reworked it would be a good prop.

Bill Rosado

[rumleyfips]

I was at Nick's place once. He told me he held a prop under a running kitchen tap to watch how the water came off the blade when he worked one. He did not tell me what to look for or show me how.

John