over prop exhaust v thru prop exhaust on 60hp evinrude

[phillnjack]

I shall ask this question on this forum as i know there many people here who know more
about props than i would ever hope to know.
to some it might be a silly question, but i realy dont know much about race props or cleavers.


I have a chance of getting a prop with the solid type hub. (never had one of these before)

Is ther anything stopping me using this type of prop rather than a thru prop exhaust ?

Will a stainless cleaver type prop omc No.387058 be ok to use with a 60hp evinrude 1995 ?
The size of prop is 12.5 x 23 inch cleaver, made of stainless steel.

what is the down side of using a prop like this if not raising the engine very high ?

Do i need to make the exhaust exit before the prop ??????

i dont realy want to cut into the exhaust if at all possible.
or is this a must for this type of prop.


at the moment i run a stainless 13x 19 and the motor revs to the limit instantly,so i know i
can go up a couple of inches, and this prop could be what i need (i hope ) to go quick.

i am going to be getting bigger carbs to make it a 70hp as well.



sorry to sound ignorant on a race forum ,but ive never delved into race type props before.



phill.

[Ron Hill]

Can you post a picture of your boat and engine? Can you post a picture of the prop you are thinking of buying.

You have asked several good questions, but they tend to sound like you are trying to shot at a flock of doves....You need to narrow your questions to one at a time.

[Fastjeff57]

I know of two cases where a thru hub exhaust motor is run with a solid hub prop (where the exhaust flowed around the hub instead of through it). The props exhibit what I call a "controlled cavitation" (meaning the boat still moves forward. In break away cavitation, the boat stops moving.) After plane off the prop 'catches' in the usual manner, as do motors raised high on the transom, and the prop works normally.

An advantage of this set up is that you can run a much higher pitched prop than you'd like and get right up on plane, with this same prop giving you the correct rpms at full speed--have your cake and eat it too!

Jeff

[phillnjack]

Thanks Jeff that is the type of answer i was looking for.


if only raising an engine plate just 2 inches above the hull bottom,would a thru-prop or solid type be best.

is the cleaver purely a go fast prop ? and not any good for mid range and holeshot ?

my boat is very shallow v at the back, 10 degree maximum with a semi pad of a foot wide in the middle.
front of boat is deep v going into cathedral then shallow v at the transom.

I know its not a race boat hull, and i know its not just a deep v.
But no reason i cannot get it to go pretty quick, im already above 40mph and engine is not taking any notice of the 19 inch prop so i would like to try something bigger and see just what it can do at full revs.

My boat and engine at the moment. 60hp 13x19 omc sst prop..
boat is 13ft 3 inch long x 5ft 10 at widest point .weight of boat on its own is 250 kilo.
The engine is 20 inch shaft, 1995 .



this one is not mine but shows the transom without engine fitted



phill........

[Smokin' Joe]

12 1/2x23 cleaver is for a raceboat, and if it's a v-bottom instead of a tunnel then you'd have to trim it to 12" dia.
Your boat is not even a fast v-bottom, 23" pitch is way too high. To run a surface-piercing prop
(like a cleaver or chopper, or any good modern stainless prop) the motor must be jacked up. Your motor's way too low. Whatever
(cupped) prop you run (probably 19" pitch) you need to raise the transom, get the
cavitation plate up above the bottom of the boat. You need to build the transom up to at least 23"
using al plates and wood.

Over-hub is just fine, accelerates better. However, if the prop is solid steel, has no rubber cushion, then you should never
shift gears with the motor running.

[phillnjack]

well atleast i now know the cleaver is not for me..
with the 13x 19 omc sst double cupped the engine blasts to wot instantly, it can definitely take a lot more prop.

my next prop on the list is a Michigan stainless ..Part no. SS0523 been told its a 12x23.
Maybe this would be a better option for me.?



phill

[Smokin' Joe]

The motor should turn at least 6000 RPM. But above 6000 you need to
run oil at 25:1. You need the best oil at any RPM.

[Smokin' Joe]

True that I temporarily forgot how low that motor's geared, 23" pitch with gr=.41
would be like 19" at gr=.5. But unless you jack up the motor the cup doesn't
give you any boost.

[phillnjack]

I shall definitely jack it up a bit for sure.
Need to find a nice lightweight jack up coz i need to keep weight on rear end light due to
not having a splashwell in this type of boat.
Might have to get one fabricated myself from stainless

phill

[Per]

Hey Phill

Look for a 22" (or even a 24"?) Raker, that might wake that boat up.

Just make sure it's for an inline 3 and V4 gearcase! The big version is far more common than the small diameter one.

And don't forget "try before you buy" if possible