need help with rigging a Yamato 102 on a glen-l Tunnel mite.

[sarge7]

Here is the problem, the Yamato has a 15.5 transom height but the Tunnel mite is built for 20" shaft engines.

Do I just hack off 4.5 inches?

Will this present problems with swamping upon deceleration?

What about a bracket that I could mount the engine to and have some future adjustability?

Glen-L suggests mounting the engine so the prop shaft is 1-1.5" below the sponsons. Does that sound right for a tunnel, i would have thought a bit higher?


Thanks for any help or suggestions you can give.

Jerry

[bh/]

Buy or fabricate a bracket that will mount the motor further aft and drop it down some. Leave the transom at 20". The further aft u go the higher u can run the motor. Maybe start at 1.5" [or even 2"]below the bottom.

[sam]

Jerry don't forget the Yamato doesn't have a conventional water pump. Set it up with drain telltales so you know you are pumping water.

Proceed with caution

[T Chance]

Back in the mid 80's there was an entry level class using a small tunnel with a Yamato 102 burning alcohol with expansion chambers. Jim McKean was building the boats and modifying the motors. They were run at Pro races. Unfortunately, however, I didn't pay any attention so I have no idea how they were set up, but the concept works. Maybe Jim or Sean McKean can offer some help on set-up.

[sarge7]

Sam, what are Drain telltales? and where do I get 'um?

I'm going to download the dillon plans for the jack plate and have my kid make it in metal shop.

Can't get him to mow the lawn at least he can work off his room and board this way : )

Jerry

[seanp3]

On the exhaust manifold there are two nipples where tubbing is attached and usually run up to the side of the gas tank. This is where the water exits the motor. Most run the tubing up high so they can take a peek back to make sure its pumping water. If the motor is setup too high it may not pump sufficient water to cool. It will get hot and steam will exit the tubing. Eventually no steam and the motor will seize.

[sarge7]

Hey I see your in Yakima, I graduated from Ike 1980, now in Wenatchee where I own a restaurant. Figured with the Columbia splitting the town I needed another boat.

Where do you run your rig, the Yakima river is horrid, Rim Rock is way too darn cold, even in August, and Vantage is over an hour to get to! or do you drop it in freeway lake?

Thanks for the help,

Jerry

[seanp3]

No, I don't run anywhere near the Yakima area. We did have a race in Bridgeport way up North of here, but it was decided to drop that race this year.

I'm a transplant from the West side of the state. My brother lives in the Belfair area and keep all the stuff over there. We test at a lake near my brother's where we grew up.

[STEVE FRENCH]

Jerry, I also have a Tunnel-mite that a friend built......I race the Yamatos and if your going to stick with them, cut the transum......We run a 1958 evinrude 30HP but I plan to leave /retire from kneel downs soon and run my 202D and 25XS (on a 25ss 15" tower) on the tunnel mite....also look'n at Mini-GT/PRO.....Hope to git some interest in region-6 (Mich/Ohio/PA/Etc....)

19P

Also;...https://hydroracer.net/forums/showthread.php?t=8433

Here is the problem, the Yamato has a 15.5 transom height but the Tunnel mite is built for 20" shaft engines.

Do I just hack off 4.5 inches?

Will this present problems with swamping upon deceleration?

What about a bracket that I could mount the engine to and have some future adjustability?

Glen-L suggests mounting the engine so the prop shaft is 1-1.5" below the sponsons. Does that sound right for a tunnel, i would have thought a bit higher?


Thanks for any help or suggestions you can give.

Jerry

[STEVE FRENCH]

If you cut trans....save the piece you take out so you can plate/sandwitch it back later....don't take the whole width off......but allowe 1-2 inches to sides of transum......once you deside how deep to notch it ..drill 3/8" hole in each lower corner and use jig saw tomake cut..
Then again how deep is the question.........run yer water tubes down the deck and spill off side near throttle/deadman so you can keep eye on it at speed.......will also save motor if ya git it pluged with sea-weed and loose water......
Keep us posted and if I get at mine sooner I'll post results.......

Then again........is there a lightweight jackplate avail out there ?

19P

Jerry, I also have a Tunnel-mite that a friend built......I race the Yamatos and if your going to stick with them, cut the transum......We run a 1958 evinrude 30HP but I plan to leave /retire from kneel downs soon and run my 202D and 25XS (on a 25ss 15" tower) on the tunnel mite....also look'n at Mini-GT/PRO.....Hope to git some interest in region-6 (Mich/Ohio/PA/Etc....)

19P

Also;...https://hydroracer.net/forums/showthread.php?t=8433

[johnsonm50]

Theres been a jackplate on ebuy but is gonna be a weight issue. If I were going to cut it, 2 holes and a jig saw would also be how. As far as height I would figure the minimum +1" so you would be able to shim up if desired and not be too hi to run 1st time out [hopefully] Good Luck.
An idea I heard about cooling is to run an exit hose forward to where you can see it from the cockpit. [dont forget to angle it away]

[ryan_4z]

I may be wrong, but I think that you want to run the water hoses above the block before you run it up the deck. If you don't I don't think that the engine will cool properly.

[sarge7]

Well I got the boat in the water and for the last month have been raising the engine to the point that I could have mounted the Yamato right on the motor board! top speed so far on a two way run with gps average 45.3

the boat porposes quite bad but that is how you get best top speed so far. I think I still need to raise the engine about one more inch as the prop takes some coaxing to run at the surface where it really performs. Also it is not a cleaver which I think it needs, this one must have too much bow lift, hence the porposing.

Do you think the solution is to eliminate the setback plate? or just keep jacking the engine and hope when the prop breaks free it will reduce the bouncing?

what is my solution? mini trim tabs?

[seanp3]

Have you checked to see if the propshaft is level with the bottom of the boat? You may have the motor kicked out rather than level. You may even want to try it kicked in a bit, which may help the porposing.

[sam]

I agree on trying the motor at different angles ... it may even be that the boat needs more bow lift to hold it steady, its hard to say without seeing it run or trying. The general answer is test, test, test