268 Sea Ray 7.4 prop size?

[darimont]

Anyone with a1989 268 with a 7.4 bravo carberated, can tell me what your running for a prop? Mine has a 17 pitch 151/2 dia. mirage stainless. The problem I'm having is at fully loaded gas, water, and five people it doesn't want to come up and plane for a long long time. I have tried different trim settings, but it will hang at about 4000 rpm until it comes up then go to 4400 at full speed. When it lightly loaded it comes up ok and it will run at 4500 rpm. I'm wondering if I should go to a 15 pitch as I would like to do tubing and some sking. I'm Also wondering what the wot rpm should be, I get different answers, some say 4500 to 4900, and some say 4200 to 4600.

Thanks
Dan

 

[Crownie2]

Re: 268 Sea Ray 7.4 prop size?

Dan - do you have trim tabs? If not you need them.

The WOT range should be 4200-4600. It won't do any good to go over. It's OK to drop in pitch as long as you remember this. You are also a good candidate for a four blade prop, like a Rev 4.

Make sure the bottom and drive are clean and you have removed all the unnecessary weight.

It would also help to know your outdrive ratio - it should be on the port side of the drive.

Bob

 

[darimont]

Re: 268 Sea Ray 7.4 prop size?

Thanks for the reply Bob,

The boat is very clean and was just put in the water 2 weeks ago, its new to me. It does have trim tabs and I have tried putting them all the way down, it seems to help some but not enought. I don't know what the gear ratio is, but I'll see if I can read it this weekend, its slipped for the rest of the year. If I go to a four blade prop would I still look at going to a 15 seeing that I'm in the right rpm range according to your specs, a four blade would decrease rpm right, so I should go down to a 15. Some have also told me that 4 blades are more for bass type boats and performance boats is this true?

Thanks
Dan

Dan - do you have trim tabs? If not you need them.

The WOT range should be 4200-4600. It won't do any good to go over. It's OK to drop in pitch as long as you remember this. You are also a good candidate for a four blade prop, like a Rev 4.

Make sure the bottom and drive are clean and you have removed all the unnecessary weight.

It would also help to know your outdrive ratio - it should be on the port side of the drive.

Bob

 

[Crownie2]

Re: 268 Sea Ray 7.4 prop size?

Dan - four blades are also used on lots of cruisers as well for the extra blade area - unfortunately it looks like the Rev 4 does not come in a 15" size. See if your dealer will let you try a 15" Mirage Plus.

Mercury Marine has lots of good propeller info on their site.

Also - I see there is a Lexor SS 15 1/4" x 15" three blade with a money back quarantee for sale on this site - might be worth a try.

Any one else out there have any ideas?

Also - yes be sure to trim all the way down for take offs and trim up when the boat gets up on top.

Tab position should be down but it is a matter of degree - you will have to play with them.

Bob