XR 4 Hydrofoil

Lancerdad34

Petty Officer 2nd Class
Joined
May 11, 2010
Messages
193
I am look at this for my Mercruiser 5.0 (25 ft Sportcraft) to help get on plane quicker. Is it worth the money?

Thanks,
Brian in Mi
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,342
Please don’t. Terrible things and known a few occasions for them to actually snap off part of the AV plate.
No excuse for them really. Nothing that can’t be solved with clever selection of a suitable prop. I’d even then you still feel unsatisfied…think about weight distribution and tankage. If even after that…smart tabs or similar would be the last resort. All the best.
 

JimS123

Fleet Admiral
Joined
Jul 27, 2007
Messages
8,162
No experience with xr4. I prefer a DoelFin. I put one on in 1985 and have had one on every boat ever since. Over 50 boat years experience. I even have a brand new spare for when I buy my next boat.

Best invention ever made. All of the problems are because the engine is overpowered for the boat, or due to improper installation.

As already said, YMMV. I would advise against it because unless you do it right you will be disappointed. Optimize with a ss prop first.
 

Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,428
As mentioned you will get conflicting recommendations. Like Jim I successfully used a DoelFin, as it helped my planning performance on an underpowered boat (3.0 merc IO). As others have mentioned it did break my AV plate... in the end I got better performance out of a lower pitch 4 blade prop.

Not sure what you are running now - if it is a black max basic Al prop try something like a Michigan Vortex 4 blade and drop in pitch. 5.0 pushing a 25 ft boat is a big task...
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,840
I think those whale tails are a bad idea. Adjustible Trim Tabs are the way to go. A 25 footer with a 5.0L Mercruiser will likely drag it's butt when trying to plane. The trim tabs can be put down for holeshot, and up for cruising.
 

airshot

Vice Admiral
Joined
Jul 22, 2008
Messages
5,080
You have a heavy boat and a small motor, so lots of force will be on the cav plate so the risk of damage will be high. These fins are designed for lighter weight boats with smaller motors to help get the stern up and the bow down. Folks have saw they work on small boats so they started pushing them onto bigger and bigger boats, and then serious issues can be created.
On a boat your size go for the trim tabs, that is what they are designed for, don't expect some little plastic fin to handle a couple tons of boat very well !!
 

Lancerdad34

Petty Officer 2nd Class
Joined
May 11, 2010
Messages
193
You have a heavy boat and a small motor, so lots of force will be on the cav plate so the risk of damage will be high. These fins are designed for lighter weight boats with smaller motors to help get the stern up and the bow down. Folks have saw they work on small boats so they started pushing them onto bigger and bigger boats, and then serious issues can be created.
On a boat your size go for the trim tabs, that is what they are designed for, don't expect some little plastic fin to handle a couple tons of boat very well !!
Thanks for all the advice! Trim tabs it is!
 
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