Prop change

[degree]

I need a little help...

I have a 1987 Mach 1 (27') with twin 330 Mercruisers. When I start out, the boat wants to dig a hole in the water and it takes me anywhere from 10-20 seconds to get on plane. On top of this, my top speed is < 60 mph.

I really don't need this top end and want to get on plane sooner as well as be able to maintain 'on plane' at a lower speed/rpm.

Any sugestions?

 

[walleyehed]

Re: Prop change

Can you give us a little info on the prop make and what models they are???
How is the RPM at WOT with a normal load?
Please include the pitch and number of blades.

 

[degree]

Re: Prop change

Can you give us a little info on the prop make and what models they are???
How is the RPM at WOT with a normal load?
Please include the pitch and number of blades.

I seem to have forgotten that I had posted on this subject before, and you replied that your personal preference (and concern) was for somethng different because Lazer II's are for high engine mounting and 50+ mph...

So, to answer your question here, RPM's a@WOT are 4500 (well within the range of 4200-4600)the pitch is 21 and three blades. Again, the boat digs a hole when starting out and the top end is in the neighborhood of 60+.

All I want is to get on plane somewhat quicker and do not mind a penalty in top end. Any help will be greatly appreciated.

 

[steelespike]

Re: Prop change

I'm no expert but::
this is the second boat your size with big twin I/Os with hole shot probs.
I mentioned the 11,400 lb wet 32 ft proline that gets up in 8 sec. with twin 250 outboards.Must be those twin I/Os are just too much in the stern.
If you don't have tabs they are a must.Of course trim in as well.If you have 3 or 4 people sitting across the stern that would slow things up.
You could go to a 19 but watch the wot rpm.Maybe the experts have a trick prop to help.

 

[degree]

Re: Prop change

You mention 'experts'. Are you referring to a site with a prop calculator, or are you thinking I should contact Mercruiser or Sterndrive Engineering and see what they might have up their sleeves?

 

[tommays]

Re: Prop change

1. did it every work ?

2. do you have trim tabs ?

3. do you trim the drive all the way down when starting ?




Tommays

 

[stevens]

Re: Prop change

You mention 'experts'.

Prop 'experts' around here usually means Dhadley or Walleyehed....

 

[walleyehed]

Re: Prop change

Thanks for the comment there, stevens...

Yes, the lasers work best on light, fast hulls....yes again, 60 is fast, but you have no blade area or stern-lifting ability built into the laser.
My opinion here is that a well designed 4-bld with features to include great hole-shot and stern-lifting ability would be a good choice.
There are some large blade area 3-blds that may be ok too....are you stuck on any certain brand?

 

[degree]

Re: Prop change

No, I'm not finicky. The brand doesn't really matter as long as it is of good quality and gives me what I want. It has been suggested that I might want to go to aluminum as they are more forgiving and less likely to transmit damage to the outdrives.

I might mention here that I had the drives trimmed all the way in. I wasn't using the tabs as the solenoids weren't working (they are now...) but have since learned that they will help; so that is one of the first things I will try when I get back on the water--once it returns to its natural, liquid, state....

 

[steelespike]

Re: Prop change

You mention 'experts'. Are you referring to a site with a prop calculator, or are you thinking I should contact Mercruiser or Sterndrive Engineering and see what they might have up their sleeves?

I was refering to the guys here. Of course if you could get the builders thoughts it would probably be helpful as well.