I have a Baron, the prop is a Yamaha 17 - K 13.5", it will do 37Knots and I hope to get more (40). 2 POB 80 Lts fuel. Motor 130 Hp 2 stroke Yamaha.
Question's, is your outboard mounted on the transom or on a pod. and do you use much bow up trim?

Hi Iana

Outbooard is mounted on transom ttrim gauge is not working at the moment but ussuall run at about 3/4 out. I need to get out on the water with someone eals driving so as I can see where the cave plate is sitting when running at WOT.

I take it that your prop is 13.5" dia and 17" pitch?

Regards

Bob

I have / had problems with ride and speed, the outboard trim making no difference. I took a spirit-level on board and sat it on the floor and found the boat was cruising bow up. Although the attitude of the boat felt alright to me.
I then moved everything I could forward to bring the bow down and experienced an improvement in performance. My motor is only a 130 hp 2 stroke, but it is extended out from the stern about 600mm.
I understood the standard HP of the baron was between 90-110 hp, so the motor weight plus the distance from the C of G made quite a difference to the boat trim.
In your case the motor is closer to the C of G (centre of gravity), how ever doing what I did with your boat may be worth a try, to see if you are still bow high.
Its not just the line of thrust of the prop that's important, but the hull should also be at its best angle so that its not creating additional drag.
Any force needed to raise the stern (trimming the out board out) requirs energy as does over coming drag. This energy is taken from the motor, and so there is less available to drive the boat forward.
I understand also the cav plate should be at the surface at cruising speed.

i Iana

The original brochure I has the hp rating as 70 - 200hp. I have a Power Boat magazine (nov 1981) review which had one firted with a 150 but they said for fishing a 115 would of sufficed.

As said, in hind sight the 175 probably wasnt one of my best ideas but at the time wanted to get the boat back on the water and there was no way that I could drop 16-18k for a new motor.

Regards

Bob

I don't know how you interpreted that, but I'm saying that the weight of the motor (more hp = more weight) will effect the trim. As you said you have your motor 3/4 trimmed up. I.e. lifting the bow up. Having a neutral trim will help not only with all up speed but also reduce fuel consumption.

 In the driveway, tape a bit of timber or poly pipe along your keel so it sticks out 10 cm or so from the transom, or use your eye, then trim your motor so the cav plate is horizontal to your keel. This would be 0 deg trim, put a horizontal stripe of electrical tape on the front of your outboard so you can see it from the helm when you look back at the outboard. Line this bit of tape up with a mark in your outboard well and then add another bit of tape there so you can tell roughly where 0 deg trim is. Get creative with a spirit level and a protractor and you can add marks for trim all the way in, 5 and 10 deg out.

A little bit of trim changes performance a lot. If you have trimmed up to far you'll lose speed and WOT revs will be high, your boat might porpoise also. Worth getting your trim sorted as running 3/4 out seems a bit much.

bobakers you said you trimmed your motor out, so moving the leg away from the transom, that's bow up, I got it arse about, sorry about that.
Obviously if you have to trim the bow up, you haven't got a weight problem in the stern.
So its a prop problem.
As I understand it, a finer pitch prop will give you initial high power, to get "out of the hole" so to speak, good for towing skis or tubes etc. The coarse pitch prop will give top end speed.
There's a bit of info on the net about this and sizing your prop.
I think it would be a good idea to have a prop that loads up your motor, i.e. the top end RPM is correct for that motor at wot.