First TestRun of a MRC CSH in Sweden

[Tmfcracing]

Hi Folks =)
With the outstanding help from Mike and Theresa I have build myself a
C Stock Hydro this winter, The boat is build from the CMH plans but the
Yamato is still all stock.
After loads of hard work I finally got it in the water yesterday, after some minor adjustment we got it to run 53 knots (60.99 mph). How do I make it run 60 knots ?
I would love to know were the motor angle should be in relation to boat bottom.

Here is the onboard video (adjust to 1080p HD) =

http://youtu.be/JDE2UUuxbus?hd=1

[ZUL8TR]

csh testing

Do you have a tachometer? We need to know engine rpm at max speed. Your engine revs sound low to me.

What depth do you have the center of the prop shaft below the bottom measured at the tail end of the shaft? Depth is no less than 3/4" in USA CSH not sure what the min CSH depth is in Sweden. Monitor the cooling water leaving at the hose at the top of the engine.

What angle is the centerline of the prop shaft in relation to the bottom?
Start with it parallel (0 degrees), if to much lift at the bow reduce angle by adjusting motor toward transom (tuck in), if not enough bow lift adjust motor away from transom. But in all cases the idea is to keep the sponsons off the water but not to high. Your speedometer and tachometer will tell the take as well as observing the running angle of the boat.

Are the sponsons lifting clear of the water at speed? They need to be off the water.

Do you have full air traps?

Do you know the average pitch of the prop?

How many blades on the prop?

What is the weight of the boat?

How wide is the bottom at the rear?

What is the length from the rear bottom to the back of the sponson trailing edge (known as afterplane)?

[blueskyracer]

Martin those are all good questions and next time you run it would help to have someone on shore video tape it so we can see the attitude. Remember to also stay back in the boat as much as possible in the straits on calm days

[Tmfcracing]

Would love a tachometer, were to find one that works with the Yamato and how to connect ?

Center prop to bottom = 3/4 inch.

Measured the centerline right now and it seem like this could be a big no no, It sits 7 degrees invards towards transom so it probably puts the boat down up front.

Prop is a 3 blade Dewald P-141. I have no idea what kind of pitch it has....Looks neat do

Afterplane and bottom wide, think Mike knows that without measuring , I dont remember.

For sure I will use a side view camera next time.

[Tmfcracing]

Anyway, It was realy fun to drive. =)
Didn´t go so hard in to the turns yesterday, 39 fahrenheit in the water so I liked to stay dry

[T Chance]

Nice job on building the boat.

[wagner-racing16-s]

The best setup I found to work was running the motor at 3/4" below the bottom and an 1/8th of an inch to 3/16 of an inch tuck under the boat.

[propnuts]

Increased speed

One of the ways we see increased speed from that setup in the US is by shaping and polishing the lower unit (gear foot), something that is not allowed if you want to race that motor in OSY. Almost any racer will tell you it's propellors that make you go fast once you have a good setup. Most of us in the states use a gauge for measuring the prop shaft angle (or tuck). You can also check it by putting a straight edge on the bottom of the boat and measuring to the front and back of the cavitation plate. the difference in the measurement is your tuck. About 1cm higher in the front will be a good starting point. From there you want to adjust it so you keep the front of the boat down in the straightaways, but are still able to keep the sponsons just off the surface of the water in the corners. Best of luck.

PS I really like the paint job, reminds me a little of the old Budweisers.

http://thunderboats.ning.com/page/restorations-1

[Tmfcracing]

Biggest Thanks for your feedbacks to this noob =).
I have made 12 different stainless steel "tuck adjust washers" with a differance of 1mm
because the original 5 adj. washer give me 7degree tuck on the longest side.
Just to wait for a sunny day and try again.
Would also be fun to get some kind of tachometer till then.

[kampkurz]

Tachometer

Try tinytach.com for info on a tachometer. Make sure, if purchasing, to get one with a wire long enough to get it in front of you.

[blueskyracer]

I would try a neutral set up- no kick in or kick out and a depth of 3/4. Do not measure off the rear tunnel surface. Go from the true bottom.