Zapcat and tohatsu 25hp engine height on transom

[Commando C2]

i have a z10 gemini, and a 25hp yr 2000 M25C tohatsu.

have just mounted the engine normally, outboard bracket sitting on transom.
lots of splash from the engine, looks very inefficient.

the water level is hitting the square section of the lower leg and the shifter gear rod.

I have read about getting the engines as high as possible and can see that my engine needs to be higher so the lip above the anti cav plate is on the water line, not sure what that is called on the engine leg but it looks a smaller anti cav type plate.

The boat seems to take a while to plane and is highly sensitive to weight in the boat. I will mostly be running with 3 people in it so need to adjust for this setup.

On the back of the boat in the aluminim transom is a curved cut out that is shaped the same as the lip above the anit cav plate. Should these 2 be lined up?

what other marks can i use? when planing the deck of the boat isnt very high above the water line unlike the videos i have seen of the racing zapcats where you can jut see the outboard leg only beneath the boat and no part of the deck touching the water

I did some turns and the prop seemed to cavitate a bit so raising the motor will surely only make cavitation worse???
i am running a standard prop so not wanting it to come out of the water like the semi cleavers.

any help on engine height will be appreciated!
pics too ideal.


thanks

[Bighag7]

Hi Mate,
I've only ever seen these with 50's on. Is your engine the right shaft length? Short, Standard or Long? The reason they get high out of the water is the speed they plane at so your 25 may not be quite up to the task.
It'll still move about, but won't offer the sheer terror that you can get with a 50. Also look at getting a Dolefin on there.
The Cav plate should be well under the water otherwise it won't be very efficient.

[Commando C2]

hi
thanks for that reply. my engine is a short/standard shaft. not sure if those two are one and the same or different lengths of shaft.
I have used the 25hp on my commando c2 3.5m sib and it planed ok.
When i took the zapcat out the other week it did plane and the faster i went the more the boat liked it and the bow lift from the nose cone kicked in more. There was just alot of spray from the square part of the engine leg hitting the water rather than the tapered part.

I have some dole fins so may give them a go as on the sib they made it plane really quick but seemed to cause more drag at speed due to them cutting through the surface of the water.
i am trying to find some pics of a zapcat with a 50 hp on it or a 40hp so can see where the tapered part of the engine leg is in relation to the bottom of the transom.
attached are 2 pics of the engine in its original postion just mounted straight onto the transom...

[Commando C2]

i have seen on some sites that the cav plate should be level with the water when running at speed?

here is the position of the engine raised up just enough so the tapered part of the engine is on line with the bottom of the transom and the curved cut out in the middle of the back of the transom!!

not had chance to try it out yet though.

if anyone has a short shaft 2 stroke tiller steer for sale let me know!!
thanks

[Slaphead]

PM sent

[Bighag7]

Hi Mate,
Short shaft and standard are different. These boats only really come to life with 40 or more on the back although I saw a nutter with a 70 on the back once.
Keep tinkering and look at Youtube they have it all on there.

[Commando C2]

thanks bighag7

i was hoping the 25 would be enough with only 2 on board so will tinker with the height and see what happens.
Been on the look out for a 40hp but they are considerably heavier than the 52kgs of my 25hp so i will struggle to mount it on the boat on my own.!!

cheers

[m chappelow]

Originally Posted by Commando C2

i have a z10 gemini, and a 25hp yr 2000 M25C tohatsu.

.

the water level is hitting the square section of the lower leg and the shifter gear rod.

try shape a block of wood and cable tie it in place like i did .
reason is my boats a short to standard and the engine is from my other boat thats a long ,after i put the block of wood in place i did away with the rubber spray sheilds that you can see in the pic .

[Bighag7]

Hi Mate,
Try these guys, they're really fantastic and they have some reasonably priced 40s in.
http://www.billhigham.co.uk/used_dat...sed%20outboard

There is a tough plastic transom height adjuster that I've seen. It just drops on top of the transom and gives some extra height if you need it.

[Commando C2]

thanks for the info

The bit of wood at the front is a good idea, will look into it.

Looking at way less than a grand for a 40hp really. i am a bargain basement boater!!
have book marked the site though to keep looking regularly.

cheers

[Bighag7]

Hi Mate,
They do have one for £799 on the net page.

[rik_elliott]

I found my zap cat ate money even though I aimed to do it all on the cheap. I had a 40hp yamaha on the back - when I finally got top performance it was brutal! But to get it to perform right I had to use a semi cleaver prop. They tolerate ventilation and are stern lifting so do away with lots of nose rise. I'm sure I read on the australian thunder cat forum (great site by the way) that dole fins aren't great on cats? They also had loads of info on how far to raise your motor for best performance. I think with a semi cleaver they suggest prop pretty well level with the hijackers - but keep an eye on the tell tail very easy to be running dry. you would def need a semi cleaver to raise your engine that far though unless you are able to get your standard prop worked to add some extra cup?

25hp probably isn't man enough to make your boat perform as it should. However I don't think that would explain the bogging down you eluded to- what pressure are you running the hijackers at?

Best of luck with it all- they are fun boats but very finicky to get running right

[Bighag7]

At last, someone that knows the difference between Cavitation and Ventilation! Whoop, Whoop!!!