Newbie needs setup guidance on Yamato 302

[SOOTY]

Hi

okay, first an apology. If any of the following statements or questions are or sound stupid, remember, I new to this lark, put me right!!

This is what we've got and how it is set,

Its a stock 302 on kneeler.

tilt is set so the propshaft is parallel to bottom of hull.

transom height set to put propshaft 1½" below hull.

fuel/oil 30:1

PROBLEM

we've tried 3 different props and it doesn't rev beyond 4500 (tacho fitted & checked)

Timing is correct, everything clean & clear, plugs changed, fuel changed, compressions good, all the obvious stuff done.


QUESTIONS

why don't it rev?
is transom height too low? (give us a clue!!)
how high should we expect to rev it to at end of straight?

SOOTY

[bill boyes]

There are no such thing as stupid or dump questions.
#1 the motor is to deep. go up to an inch and see how the RPM is, then a little higher. You should me ok at 3/4" The CSH class rules is 1/2 below the bottom. DO NOT GO THAT HIGH or you may run out of water to the motor.
#2 I do not like the 30 to 1 mix. I run my 302's and 102's at 20 to 1. That is 16oz to 2 1/2 gals of gas. Some owners use more oil than that.
#3 we have seen 6800+ rpm
#4 timming should be about 240 degrees
What boat do you have?

Where are you from? try to hook up with someone in your area and ask for their help.

[SOOTY]

thanks Bill will try it

Hi Bill

thanks for the tips, also see PM.

30:1 (what the book says, didn't know any different)
what is the benefit gained from running with so much oil?

Will raise engine as suggested next time out.

Boats a Ringwood

sooty

[SOOTY]

just a thought,

if you are running 20:1 mix, do you still run standard 0.020 plug gap??

sooty

[SOOTY]

Hi Bill

ended up raising about 5/8". Transom needs modding to go higher. That will be done for next race, unfortunately no opportunity to do testing in between.

Now seeing 6200rpm regularly at end of straights, so will be going in small steps for the last few hundred rpm.

So far, we've gained about 2 seonds a lap and its noticably quicker off the line.

Timing, is there more than one way of setting it? we've done it as per the Yamato manual. Is there a better way??

Sooty

[Tim Weber]

You need more RPM. You should be in the 6900-7100 range. Your props may be too stiff or your boat may have some problems. Are you running a hydro or runabout? There are lots of little things you have to attend to.

On timing the motor, use a dial indicator, find top dead center, move the stator to match the notches on the motor. A runabout runs between 200-225, a hydro about 240.

High speed needle set at about 1 1/4 turns, run it then check the plugs, rich it or lean depending on plug color one click at a time

Low speed needle open about 2 turns, 20:1 is a decent mixture, you can run as rich as 12:1. Do not run synthetic oil if the motor has new rings right away. The rings will not seat. Break it in on petroleum based oil then you can switch if you like.

Most important, find somebody who races in your area! Any racer will be more than happy to help you. The stuff above is basic. For the fine tuning, you will need some help and lots of testing.

Have fun.

Tim

[SOOTY]

Hi Tim

thanks for the input.

we are in Europe and the boat is a Hydro Kneeler. We don't get the oportunity to do testing due to speed and noise restrictions. All our "testing" is done during race conditions.

The reason I came to the forum was, we are getting very conflicting advice locally.

Props, the props we've got came off a competitive boat.

Boat, won a load of trophy's last year.

Engine & setup are the unknowns.

Engine basic's, compression etc all okay.
Mixture not along way off going by the plugs.

Transom will be sorted for this weeks meeting, so will be going up a bit more until we get the rev's. But will look at the timing again and will also look at carb settings.

I think what we have established is either the engine isn't producing the goods or the setup is miles out, although I think we can assume the engine is good, as it notably better than the old one and it was sold to us as A1.

As we've already seen improvements from changes made from advice off this thread, we'll play with the guidance so far until we get no further gains.

Other basics we would like to establish though, are,

plug gaps
and the relationship between hull bottom and propshaft, Parallel??

Bill and Tim, thank you to date,

Sooty

[sam]

Rather than looking for max revs while raising the engine, be aware that you may stop pumping cooling water up to the motor before you stop increasing motor and or boat speed. Yamatos do not have a water pump like fishing motors, nor do they use ram water intake like Rossi or Konny. Instead water is forced up into the motor by spray from the prop. Raise the motor too far and you can affect this spray feature (in a negative way) while still traveling very fast

[SOOTY]

Thanks Sam, I'm aware of the cooling issue and we do keep an eye on it each time we shift up.

Must admit it does seem a bit of a daft way of cooling when ram feeding would have been just as simple but much more reliable.

sooty

[sam]

In their original use the prop spray cooling pumps up better than ram water would. They have some kind of pre-start set up where the boat is held stationairy until all motors start or something. Motors that start early are pumping water up even though the boats aren't moving, this wouldn't happen with ram water inlet. When the race officials are ready the boats are mechanically released and they bolt away from the dock and then slow down and enter the starting gate.

All their boats are identical, too; their professional racing is much different from our (and their) amateur racing.

[SOOTY]

Collared By Rex King!!

so now i realise how small this sport really is!

At the start of this thread, I tried to be vague about who and where we were deliberately so as not to offend any locals who had offered advice. Within 2 weeks Rex King walks up and presents us with a photo of our boat titled "sooty at Oulton Broad"!

Rex has given us some good advice and I'm sure there is more to come. Also now talking to an experienced pit crew.

Also appreciate the guidance from this forum, its been all good. Last few weeks we've felt we're actually getting somewhere!

Sooty