kevlacat 5.2m yamaha high thrust question

[johntsang]

hey guys

i have just upgraded my old 70 2stroke yammies to the new high thrust 60hp efi 4 strokes.
my old 70s were only long legs so had to get modifications to my pods so i can run the new extra long legs.

after the first run ive found the power out of the hole better top speed is only at about 26knots with the 15" props though,as opposed to the 30-32 knots with the old yammies.

my main problem would be the amount of water that seems to be getting thrown on the outboard and around the outboard when going at slower speeds and sometimes when cruising.

i never seemed to have this problem with the last outboards but the last out boards had trims on them (see pics below),do you guys think i should fit these trims to try and eliminate the water spray?

the boat handles awesome with the new donks and they are sooooooooooooo quiet! They start first kick too haha something im definetly not used to with the old 2 strokes.

have a look at the pics guys and tell me what ya think.like i said my biggest concern is the amount of water splashing around the power heads.

cheers johnny
http://img149.imageshack.us/img149/5908/dsc08222hv5.jpg (http://imageshack.us)
http://img504.imageshack.us/img504/7667/dsc08223zh5.jpg (http://imageshack.us)
http://img504.imageshack.us/img504/7667/dsc08223zh5.195537cb43.jpg (http://g.imageshack.us/g.php?h=504&i=dsc08223zh5.jpg)

http://img89.imageshack.us/img89/877/dsc08224cc8.jpg (http://imageshack.us)


http://img178.imageshack.us/img178/593/dsc08225wt1.jpg (http://imageshack.us)

http://img178.imageshack.us/img178/6903/dsc08226sk0.jpg (http://imageshack.us)

http://img89.imageshack.us/img89/8919/dsc08227bh3.jpg (http://imageshack.us)

[Finnatical]

Johnny,

I have a KC2400 and it is very wet at the back, particularly when coming off the plane water sprays all over the powerheads. I have been told by some that it is just a cat thing although I am not convinced. I thought it might have something to do with the spray plates mounted higher on the legs but your new motors seem to have them factory fitted for want of a better description, as do the Suzukis fitted to my boat. Even during normal running in average seas the back of my cat is a very wet place to be as I beleive it is in most cats. I would be interested to hear others opinions on whether the spray plates make any difference.

I can't comment on the performance side of your post as I am not much a of cat expert just yet.

Good luck and good choice in motors, I am sure they will give you years of trouble free and cheap running.
Regards,
Jason

[Greg P]

Johnny

Give Trent (Fly_1) a PM as he has been through all this in his KC

Look here ---- http://www.ausfish.com.au/vforum/showthread.php?t=67347&highlight=high+thrust

[Dean1]

Hey Johnny it might be coz of the spray plates mate, mine is very dry with the 70's with the plates on, ill talk to gav and see if he's runnin em on his f 60's. As for speed he was getting roughly 26-27 kts but now getting 32 kts now that the motors have freed up so dont panic about speed mate;)

[johntsang]

Hey Johnny it might be coz of the spray plates mate, mine is very dry with the 70's with the plates on, ill talk to gav and see if he's runnin em on his f 60's. As for speed he was getting roughly 26-27 kts but now getting 32 kts now that the motors have freed up so dont panic about speed mate;)

hey dean:)

yeah i remeber you saying that in one of your PM's so i am just hoping they free up after a few hours;)

i am only getting about 5100 rpm wot

johnny

[goldcoastau]

Hi There
Great reading this thread. Compelled to ad my 5 cent's. To me it seems if you have enough horses you don't really need the foils. However take my little boat and ask of it a heavy duty job - then it certainly requires foils. I have tested heaps and there's no doubt without foils its a pig & with foils she is sweet. The boat is a 16 ft Markham Hookem fitted with 2 60 hp four strokes high thrust Yamahas. Mostly we run with 5 guys ,big esky ,dive gear and fishing gear. Amazing what a little boat like this can do running big distance. We do things like starting at the Seaway to Jumpinpin - have a dive and fish - heading north to boat rock & sevens (pt Lookout)- fish and dive- run to Rufus King wreck in the south passage-then back to the Seaway. The foils i run are the heavy duty stainless Lazers by Solas.

[STUIE63]

Johnny check which props the other guys are using 5100 rpm is probably not enough you will be causeing damage to your engines
Stuie

[FNQCairns]

If your motors are fitted too low they will throw lots of spray, 'batwings' is a good description, is one throwing onto the other? or is it the hull due to the extra weight? Possibly you need to go up 2 holes, if it all works well you may see a knot or two extra as a big guess, I don't know cats but the batwings are universal.

cheers fnq

[jimbo59]

When i looked at the motor height i was a bit worried,they look like they could go up a few holes.When your only just planeing the water is coming up and smashing onto the trunk of the motor,part of the problem is the pods.The pods should follow the flow of water and not interupt water flow....

[johntsang]

gonna talk to the guy who fitted the engines about lifting them up a notch or 2.problem is they have mounted it on the top hole so they will have to drill new holes:-[

johnny

[fly_1]

I have just fitted the spray deflectors on my 4 strokes, and all the cross spray I used to get thru the mid range speeds has gone. The original 2 strokes had them on, but after putting the 4 strokes on I never got around to it. Anyway, after speaking to a mate from Kcat ( one of the owners), he gave me the template for the deflectors. ( They were originally for the F100, although the F60 and 80 's also use the same deflectors). Got a couple made up, and put them on, and now the problems fixed!!!
The photos attached show them. Note they are much larger than the original ones for the 2 strokes. No performance cosiderations at all, just stop the spray.
On monday we also spent most of the day with Steve from SOLAS props playing with the engines / props etc. To start with we raised the motors one hole ( 3/4 inch), then went and water tested the boat with 5 different props. To everyones surprise, (including Steve ), we have decided to keep the 15k yamaha alloy props. It gave us the best overall performance. We played with 13inch props, 15 inch props, and Steve even tried the 4 blade props.
To cut along story short, the 15inch alloys gave me the best cruise with good out of the hole performance, and WOT speed as well. We ended up with WOT of about 5500 - 5600 revs, and 30 kts. Cruise of 4700rpm for 23-24kts, and hole perf pretty good. ( as good as the old 2 stroke 70hps).
The main factor most people are having with the repowered 5.2m kcats, is they are running the motors to deep. By raising the engines, you will make the required revs, ( yamaha specs of between 5500 -5900). I have been surprised how much difference raising the motors actually does. I am now unable to raise them any higher ( without drilling more holes, and welding a higher pod on to it), but if I could, we would raise them one more hole!!!!.
Overall, both Steve (solas), the mechanic and myself all agreed the 15k alloys were the best for 90% of the type of boating I do.
(just for interest sake, if you were carrying really big loads, you would run one of the 13inch stainless models we tried, as the hole performance was unbelievable, they got the 5800rpm, but top speed dropped to around 25kts!!)The local pro crabbers run these.
Hope this helps those who like me, were having a few dramas with the prop setups.
Regards

Trent

ps, you can also see the transducer bracket we have made. Rod from furuno was impressed with the readings we are getting with the new electronics. We get a clear picture ( both 50 and 200khtz) at speeds to 26kts, in most seas.

[finding_time]

Johnny

Sorry i took so long with these shots! Agree totally with Trent! My motors have spray deflectors as you will see in the shots. They work perfectly!! The motors stay very dry. I have trimmed the motors down and run a straight edge so you should get a great indication of height. Hope they help.

Ian

Ps my spray deflectors are made of the vinyl cutting board material

[Outer Edge]

John,

100% you need spray plates ....................and possibly UP a hole or two .

Outer edge.

[finding_time]

Trent

Just looking at the last shot of mine and trying to imagine your motor trimmed right in i reckon my motor is a little higher than yours. I seems to work well at this height! See pic;D

Ian

[johntsang]

guys you have been a fantastic help!


fly and findingtime i really appreciate your help.
i just picked up the bot from the shop.they have taken the motors off and im going to add another 90mm to the top of the pod,with the hook of the outboard sitting on top of the pod i will get 20mm lift on what i have now.and where gonna work up from there.

im gonna stick with the 15inch prop,at the moment with the motors low im only getting around 26knots so hopefully i get more once we lift them up.

Ian that pic is bloody unreal!

one thing i did notice with the new donks is the amount i can lift the nose up. the KC rides so much better without the hydrofoils.

guys thankyou again for the pics and all the help.

next on the list is
outriggers
targa bar
baittank
mmmmmm more money

johnny

[Dean1]

Hey johnny hope you sort it out sweet mate. Get yourself those sprayplates as well. 90mm seems alot to raise on top of what you have? Have they already raised the top of the pods to suit the new motors?? Looking at trents transducer the way its mounted, i think i have mine way too high. Hi trent, mate where did you purchase that bracket mate i had to make my own?? Is that for a 620 furuno?? An answer would be much appreciated ;D Ill take a pic of my hieght of transducer and put it on here. Here is a pic of gavs boat, motor/pod setup(gotta love the green) ;D

[johntsang]

Gday Guys

quick report on how i went second time around hehe

took the boat back to the shop and we came to the conclusion the motors were too low.
bugga no more meat left in the pods to drill higher,so off they came again to be lifted up another 90mm.

motors are fitted and went for a run today.we managed to get to 29knots(gps reading) and WOT was around 5500-5600 which is alot better.
seemed to get what i would have thought to be cavitation at wot.but im not 100% sure if thats what it is.
still have a lot of wash around the motors so im going to try the spray plates for sure.
out of the hole performance is better than the old 2 strokes still.
heres some new pics.
http://img521.imageshack.us/img521/4613/dsc08298gd2.jpg (http://imageshack.us)
http://img521.imageshack.us/img521/4613/dsc08298gd2.68d08c125d.jpg (http://g.imageshack.us/g.php?h=521&i=dsc08298gd2.jpg)
http://img166.imageshack.us/img166/7324/dsc08301ad5.jpg (http://imageshack.us)

johnny

[bbss]

You can make the spray plates very easily. All you need is some sheet alluminium and a jigsaw. Mine were a fair bit larger than trents and worked a treat and cost next to nothing. 15k are the right prop.

[finding_time]

John

They look to be identical in height to mine now mate and i'm sure the motors will free up abit

[evo001]

Johnstang,

What sort of economy are you getting out of the 60's?

I'm looking at repowering from 90 Yam 2st and considering options, economy is a big factor these days.

[Dean1]

Johnstang,

What sort of economy are you getting out of the 60's?

I'm looking at repowering from 90 Yam 2st and considering options, economy is a big factor these days. Mate Ian 'finding time' tells me its roughly 20-22 ltrs/hr for both motors or 1.6klm/1 litre for both. Im in the process myself. Cheers.

[Maccas]

Hey Dean,

What sort of economy do you get out of your 70HP 2 stroke Yammies in litres/hour. Have you done the numbers on changing to 4 strokes versus buying the extra fuel used by your 2 strokes.


Cheers,

Maccas

[Dean1]

Hey Dean,

What sort of economy do you get out of your 70HP 2 stroke Yammies in litres/hour. Have you done the numbers on changing to 4 strokes versus buying the extra fuel used by your 2 strokes.


Cheers,

Maccas Hi Maccas, i get 1klm/litre with the 70's or about 30 litres/hr roughly. Theres 4 other reasons why im buying the 4 strokes which is hopefully 10 years trouble free motoring (new motors) heaps quieter, heaps smoother and no more 2 stroke fumes (gettin to me lately). 5 reasons 5th been more economical as Im going to using this boat alot wide off agnes soon so they will really be worth it I think mate. Cheers.

[finding_time]

Dont forget range Dean!! Your going to gain 30% more range!

Ian

[Maccas]

Hi Dean,

How many hours have your motors done, cos mine have only done 37hrs. So I think I should keep them for a year or two cos I would buy a lot of fuel for the changeover to four strokes especially as I do more bottom fishing than trolling. What would my motors be worth (2004 models) ? of course range increase would be handy.:-/

cheers,

Maccas

[Dean1]

Hi Dean,

How many hours have your motors done, cos mine have only done 37hrs. So I think I should keep them for a year or two cos I would buy a lot of fuel for the changeover to four strokes especially as I do more bottom fishing than trolling. What would my motors be worth (2004 models) ? of course range increase would be handy.:-/

cheers,

Maccas I just saw a late model for sale for $5750 and a 91 model for $3750. Youd get around $10 000 for the pair id say im hearing ill get 7-8k for mine. I dont troll either, i guess a way to look at it whatever motors you have are going to depreciate so they might as well be four strokesand enjoy all the benefits of a four stroke. Hope this helps, Deano.

[Dean1]

Hey Ian what do you think about the current height of my 70's?? Way too low hey! This may explain why my WOT is 30kts when these should be topping out at 34kts. I'll get my new f60's up out of the drink.

[Dean1]

Pics wont load up :-/