Planing problems - help needed!

[SeaRayViking]

Sorry, if these issues seem obvious or ridiculous, but i'm relatively new at this.

I've bought a 1989 20ft Sea Ray 200cc. A lovely small (but quite heavy)cruiser with a Mercruiser 4.3lx with 205 hp. The boat was originally equipped with an Aplha One gen. 1-drive (gear 1:84) and i 've just mounted a used, but well-working 1:84-drive.
According to Sea Ray's operator's manual the boat with equipped with a 3-blade prop with a 13, 75" dia and 21" pitch.
However when i bought her it was fittet with a 5-blade High-Five with a 23" pitch.
Everything seems to work just fine. Gears, RPMs, oil pressure - everything - but she really struggles to get up on plane!!?? And with three persons in the boat it takes forever!!?? (The sound of the eninge gets really dark just before it gets out of the water - and after that it just sails like a dream)
Can anyone give me a hint about what might be wrong?
Thanks

 

[Bondo]

Re: Planing problems - help needed!

Try a 21" pitched prop,....... Or even a 19".........

A 23" is Obviously Too Big........

 

[SeaRayViking]

Re: Planing problems - help needed!

Hi and thanks for the reply,

I thought it was that I had to do-
how ever , I was just quite confused, because i talked to two prop-dealers.. One of them told me that if the boat "born" with a 21" three-blade, then i should definitely use the same pitch or bigger - if i was to use a 5-blade High-Five prop... And of course the next dealer i talked to, told me exact opposite -like you say; downsize to about 19"...

Would downsizing not increase RPM? (It actually can take another 300-400 @ wot)

 

[Jdeagro]

Re: Planing problems - help needed!

First of all we need to assume your engine is running OK.
Second, we should know what RPMs you are able to get at full throttle, and what is the recommended RPM range.

Third, you are looking to climb out of the hole easier, and here you have two choices; Climb out of the hole or eliminate the hole.

Since the most popular solution is to make it easier to climb out of the hole and this is a prop forum, the answer is easy.

Changing prop pitch and diameter is the same at changing gears in your car.
If your driving up a big hill you down shift into a lower gear. Similarly in a boat you move down in pitch. However, since you do not have other gears to choose from, going down in pitch is like driving arround in second gear all of the time. This means more engine revolutions at every MPH. It means more fuel used, and less top speed.

Four and five bladed props, such as your High Five, are expensive option, and give you more torque at lower RPMs. In some cases they will tend to limmit the top speed.

The second option is to eliminate the hill so that the existing prop thrust is used to move forward not drive up hill. The advantages are being able to use the prop that keeps you in the correct opporating range at full throttle (not over Reving the engine), save fuel because the engine turns less per MPH, and have better acceleration, lower bow rise at any speed, and cruise at lower speeds on plane.

You choose!

 

[tmh]

Re: Planing problems - help needed!

Bondo is right, of curse, sounds like too much pitch. Depending on what's important to you, maybe a 3-blade 21" or 4-blade 20" sounds right. Should help in many aspects. However, Hi-5 is considered great for hole shot, if properly sized.

Interesting you are getting even within 300rpm of WOT recommended range? What are the numbers - rpm and speed at WOT?

Also, a broken record here, but Smart Tabs will make a huge difference in how quickly and easily your boat planes. Search for info about them.