Boat does not Get up on the Plane

[majed1965]

I just purchased a 6.2 metre Swift Craft cruiser boat with a 200hp johnson. Hull & motor are around the early 80's model. Its a huge hull with a huge cabin.

We took the boat out for a run but it would not go onto the plane. There is no RPM gauge to determine how its going. The mechanic jumped in and said the engine is running A1 and the carbies were good. He said the issue is with th propellor. It has a 21 pitch propeller which is too big. He recommended before we buy one to test out some smaller pitches starting with 17 and then 15 and see how it goes. It would not get up on the plane at all with the 21 pitch which is very odd for a motor the size of this.

The outboard is apparently revving perfectly but boat is not moving quick enough to get onto the plane.

The marine mechanic will try a couple of different size propellers and is installing a RPM clock.

The boat hull is in excellent condition with no water leaks. This has been a trailered boat only.

I am surprised though (probably my inexperience) that a 200hp outboar will still struggle without the proper propeller.

Does the propellor pitch make that much difference in power?

The outboard is a V6 vintage. I had a new water pump, impeller, new head gaskets and full survice done. The marine mechanic assures me the motor is running fine. I asked him to check the compression of each cylinder...still hasn't done it.

The motor it seems did come off a lighter boat. This is not the original engine for this boat. So i am hoping the propeller fixes the issue, but i am still worried it may not...

[dreemon]

Awsome looking boat !!! the right prop will make a huge differance , rpm gauge , your going the right direction, good luck

[Steeler]

Hi Majed1965.If all is good with engine then yes more than likely prop pitch.Going from a 21P to a 17P or 15P will be heading in the right direction even possibly a 4 blade which may slightly reduce top speed but will help with your hole shot ( take off ) and assist with holding it on the plane.Cheers Steve.

[FNQCairns]

Think of it like this, any outboard will (should) reach it's sticker horse power only when it reaches it's top rpm range. If the engine is only spinning at say 4200rpm it may only be outputting 50% of it's sticker HP as thrust and doing it in the most inefficient way it possibly could.

Take particular note of the diameter, often many reach their chosen rpm but the large diameter passivates 20% of that HP as resistance, it's the pitch that propels the boat.

Whatever pitch put's you close, any larger than 14.5 diameter will end up as wasted HP unless you tow a barge every now and then.

cheers fnq

[majed1965]

Most people i have spoken to have also stated that a 21 pitch propeller will make the boat sluggish, but i thought to myself that it doesn't matter how sluggish it is a 200HP should still be able to get the boat onto the plane....but it seems i am wrong...

This is an extract i got from a OMC outboard manual.

"The propeller is the final link between the boat's drive system and the water. A perfectly maintained engine and hull are useless if the propeller is thw wrong type or has been allowed to deterioate"

Lets hope they are right....will test out again tomorrow...

[FNQCairns]

And worse than that lugging is the fastest way to send a well looked after and mechanicly good engine to an early grave, from what you have stated already I would only run that engine/prop combination on muffs.

cheers fnq

[foxx510]

Interested to hear how it goes. It is a great looking boat, would love to see some more pics.

[INTIMIDATOR]

Hey Mate
You can try giving Steve at Solas props a ring.
He will give you some free advice on what pitch ect will suit you needs
But what has been posted so far is on the money!
Payney!

[Angla]

It looks like a beautifull boat. I would like to see some more of the inside if it were possible.

Does it have a leg and how is the propeller and cavitation plate height in relation to the bottom of the hull?

I am sure you will find the problem quickly.

Chris

[Steeler]

Real good point made by Angla regarding the cav plate height

[ozbee]

start with a 17 pitch will make all the difference

[majed1965]

Here are some more pics as requested.

[kokomo]

have you ever tried starting your car from a traffic light in 5th year?

it does not matter if your drive a 6lV8 or a 4c 2l.. still going to be a piece of shit from the lights!

just because its a 200hp does not mean it will plane... why on earth would it mean that?

TBH if the motor is 'ok' then the prop is 100% wrong..

invest in a tacho.. change props.. make sure you can get full RPM..

remember you only get full power at full revs...

[gofishin]

...We took the boat out for a run but it would not go onto the plane. There is no RPM gauge to determine how its going. The mechanic jumped in and said the engine is running A1...

...The outboard is apparently revving perfectly...

These statements are contradictory. Not sure how he knows it is revving perfectly without a tacho, and when it can't plane. If it's revving to max rec revs and not planing you have spun a bush, or is ventilating very badly. As angla suggested, check the engine height. Regardless, you will need a smaller prop. That vintage O/B will be flywheel rated, and it is a big boat, hence you can't compare hp's to newer O/B's. My guess is trial a 17 and work from there.
cheers
PS the tacho will be money well spent

[MyWay]

tray dis one should fit it perfect to it
and you may get for rely good price
http://www.ausfish.com.au/vforum/vbc...hp?do=ad&id=16

myway