270 Sundancer Performance

[Miller's]

we have a 97 with the 7.4 and it has tons of power, it moves the boat like it was a toy. we had a 21 ft liberator with a omc 460 and the sea ray seems to get on a plane quicker. something is not quite right with your boat and prop

 

[No Name Sea Ray]

-Update-

I put 22 pitch props on and a new tach, it goes well now. I max out at 41mph at 4000rpm with the drive trimmed up and trimtabs up. So I could probably even go lower pitch but I think I am good at 22p.

I had five people on the boat and it got right up on plane at about 2800-3300rpm. Might hit 4400+ rpm on that rare perfect flat windless day, lightly loaded.

Stock props were 26p, engine 4400-4800 max rpm range.

The lesson is- Props make a big difference and the stock ones might not be the best choice.

 

[Lazy Daze]

Thanks for the update!

Problem though: That's not good for your engine if you can't get it into the spec'd WOT range. Ideally, you want to be able to get into the upper limit of that range. Not that you would go there much, but it is much better for the overall health of your engine if it is capable. In your case, what it means is that you are lugging the engine and making it work harder.

 

[magster65]

Thanks for the update!

Problem though: That's not good for your engine if you can't get it into the spec'd WOT range. Ideally, you want to be able to get into the upper limit of that range. Not that you would go there much, but it is much better for the overall health of your engine if it is capable. In your case, what it means is that you are lugging the engine and making it work harder.

I only 1/2 agree with that. Higher wot rpms means there's less load on the engine, true. If you prop to run at the lower rpm of that scale you'll load the engine more but you'll also enjoy a lower rpm @ cruise speed. One thing you have to watch is that boat has to be able to make the transition to plane without lugging / dragging the stern 'forever'.
Manufacturers mass produce engines for the public (lotsa' dummies) so they err on the side of caution. Prop for the lower rpm and don't 'push it' when you've got a heavier load in the boat. You'll find a slightly higher top speed and better economy too.
Try it.

 

[Woody]

Go back and read his last post. Something doesn't make sense. Why isn't he picking up rpm as he is dropping down in prop. These are two of his comments:
I max out at 41mph at 4000rpm with the drive trimmed up and trimtabs up. So I could probably even go lower pitch but I think I am good at 22p.

Stock props were 26p, engine 4400-4800 max rpm range

 

[No Name Sea Ray]

Woody- In reference to your comment on-

"Stock props were 26p, engine 4400-4800 max rpm range"

The engine is supposed to have a max range of 4400-4800.

With the 26p props I am not really sure were I was because my tach was broken. I do know when I could get it on a plane I could get to about 35mph and I believe 3800 rpm.
But with a 4+ people on the boat I could not get on a plane.

I hear what the others are saying that I should be in the max rpm range and I will keep an eye on that and consider going to 20 pitch props. The engine sounds a whole lot louder now as it is reving way more, not being lugged down. I thought going from 26 to the 22s was a big step and I am happy with the new performance. I'll see how it runs in different conditions and consider another prop change probably in the spring.

Thanks for all the suggestions.