prop professionals,I need advice

[crazy charlie]

I need a recomendation Prop Professionals.I have a 1988 280 regal,twin 5.0lx alphas,8800 lbs dry,wot44-4600,.I currently have 141/2x17 cupped props.It takes a bit to get on plane and that does not bother me.Once it gets on plane I cruise at 3100 rpm-23-26 mph and she is really fuel effecient.The problem is when there is a chop I would normally trim the drive up(on my previous boats) until the bow was raised enough to take the chop better and get the bow really up in severe weather.When i trim up just a bit the props start to cavitate almost immediately.I cant get the bow up unless it is dead calm on the water.Even with the trim tabs all the way up.What size props should I try??? Charlie

 

[cobra 3.0]

Re: prop professionals,I need advice

Can you use larger diameter props? I get almost no cavitation when I use my max diameter 14" prop and yet do with a 13" diameter.

 

[walleyehed]

Re: prop professionals,I need advice

Larger diameter props may work, but I have the feeling that as heavy as that boat is, extreme trim is going to do exactly what you say it's doing......You have trimmed beyond the point of "max leverage". on plain, you may not be able to lift the bow as you wish. Off plane, however, you should be able to get close to full trim without ventilation, to keep the nose up, as it will be up more than normal anyway at low speed, off plane....

 

[crazy charlie]

Re: prop professionals,I need advice

I only trim it a little before it starts to cavitate.I need different props but I am not sure what to change.Charlie

 

[kenneths]

Re: prop professionals,I need advice

The props you have now, the 14.5X17's, are they merc or michigan wheel....I assume they are aluminum???<br /> 14.5 diameter should give you a good bite.<br />Are you sure these props are cupped thru the trailing edge....does the cup form a hook shape by following the mid point of the leading edge, and continue on around the trailing edge, or is JUST the T.E. cupped???????

 

[crazy charlie]

Re: prop professionals,I need advice

Yes Kenny they are aluminum and both cupped.One is a michigan and the other came with the boat.I think it is called a Flo torque.It has a removable hub.I think these are speed props for this boat because it takes a while to get on plane and when it does ,it really goes.It does not seem to me like it is getting enough bite to raise the bow.My previous boat had a single i/o with a 16x14 prop.it was defenitely extreme but it lifted the bow as high as you wanted it.I may try doel fins on the drive first to see if that changes anything.Charlie

 

[tylerin]

Re: prop professionals,I need advice

Don't know the slightest thing about twins, but shouldn't the props be matched? The same size prop by differant manufacturers can give you diff effects. No experience w/ twins but food for thought. Good luck

 

[Ralph 123]

Re: prop professionals,I need advice

Orginally I had cleaver SS props and no hydrofoils and I had a problem keeping the bow down on a 79 Formula w/ twin 350s (5.7L). 6,600 unloaded and no fuel. I then moved to cupped props and hydrofoils and now it's no where near like it was. So you might try less cupped props (akin to cleavers) and/or removing any hydrofoils you may have. If you have trim tabs shortening or removing them may also help.

 

[kenneths]

Re: prop professionals,I need advice

Bottom line...If you are cavitating (ventilating) on plane you do NOT want to go to LESS CUP with the trim where you say it is. Un-cupped props ventilate MUCH easier than Cupped props.<br /> Also, I believe you are shooting yourself in the foot by running 2 different props-they should be the same.<br /> Just because the stamped pitch is the same means ZERO as to comparible performance.

 

[Spidybot]

Re: prop professionals,I need advice

On a smaller boat my similar problem completely went away by getting a HighFive prop. It bites (or 'has grip') way, way beyond the original 3-blade alu.<br /><br />I know that other props has better grip than the standard alu too, and you might find a better price (2x HighFive aint exactly inexpensive)!<br /><br />The 5-blade ss has more blade area, is a more sophisticated design and makes a smoother run.<br /><br />And yes - agree on the two different props you have: They are NOT alike and will spoil the harmony of two identical props.<br /><br />Are the both LH rotating or are they counterrotating?

 

[Ralph 123]

Re: prop professionals,I need advice

Maybe with cleavers it has more to do with the blade design than the degree of cup. Sure know that's what they did on my boat.

 

[crazy charlie]

Re: prop professionals,I need advice

Thanks guys.The 2 props are std rotation and they are the same size.There were 2 flo torque (removable hub) 141/2 x 17 props on it when i bought it but 1 needed to be replaced and they did not make that size any more so I bought a standard 141/2 x 17 prop.They both cavitate at almost the exact trim level so they seem to be acting alike so i doubt if the difference in props is my problem.I need a little more bite is what it seems like to me.Charlie

 

[crazy charlie]

Re: prop professionals,I need advice

I saw 15x17 props available,I wonder if that is too little of a difference?????????Charlie