Planing Issues

Trad · Mar 25, 2010

HELP!

I just bought a new 2008 14' Ultracraft CT with a 25 hp Mercury 4 stroke tiller (power trim and tilt). It takes me about a quarter mile to get the thing on plane (alone or with 2 people)! It's terrible! My old 1986 25 hp Johnson on a 14' boat is up in 50 feet! I was told by the dealer that a "Doel Fin" would fix the problem?? Prop problem?? Any help would be greatly appreciated!

Bondo · Mar 25, 2010

Re: Planing Issues

Ayuh,... Are you trimming in to launch,..?? Are you getting the right rpms at WOT,..??
What kinda prop is on it,..??

Trad · Mar 25, 2010

Re: Planing Issues

Thanks for the reply!

I believe the prop is a 9.5/11. There is no way for me to tell what the rpm is, it does not have a tach. I did try to look under the hood to see if the throttle was opening up all the way, it seemed to. I thought it might have a governor on it!

180shabah · Mar 25, 2010

Re: Planing Issues

The prop is the governor - when you run out of power, it stops spinning faster.

Whale tale is just a band aid for a bad setup.
In addition to the questions Bondo asked, what is the height of your AV plate in relation to the bottom of the hull? And we need specifics for the prop data, guessing won't help.

Trad · Mar 25, 2010

Re: Planing Issues

Thanks 180Shabah, that helps a lot!

steelespike · Mar 25, 2010

Re: Planing Issues

You could get a tinytach about $40 and an easy install.Be sure to get all info before purchase.In your setup hand held is probably best.
I think the small 4 strokes need very careful setup and prop selection.
The fin should be a last resort after extensive work on your setup.And in that case
smart tabs may be a better investment.
If your battery(s) and gas are at the transom you should move them forward.
If the transom has a flat angle the motor may not be able to tuck under enough.
How does the max speed seem to be?What is the dry weight of the boat?
Checked a similar boat with a 30hp etec 570lbs dry.200+ lb driver and gear 12" prop
27.6 @ 5,800 planes in 5.23 sec.You dry weight is 475 so your 25 is at a little disadvantage but should surely get up in 8 or 10 sec. wth the correct setup.

Trad · Mar 25, 2010

Re: Planing Issues

Thanks Steelespike
I will get a tach. I can't help thinking something is wrong with the motor setup. Where should the cavitation plate be in relation to the bottom of the boat? I noticed that the motor doesn't actually rest on top of the transom, it's about an inch higher. (the motor is actually bolted to the transom). I've had boats almost all my life (2 stroke motors) and I never had this kind of problem!

steelespike · Mar 25, 2010

Re: Planing Issues

Typically they usually end up about 1" above the bottom.
It appears they attempted to get it up some.I usually recommend raising it to a point just before venting(cavitation)becomes a problem.
Your 11" pitch is right in the middle of the size chart in the prop section and has the most choices.My guess is that at 475 your boat is a little heavier than the typical 25 hp application.Etec 25 was tested on a 280lb boat and ran a 12" prop at 6,000 and 31.6 mph. The etec would run a higher pitch than your Merc.
Once you get a tach and with a gps you can really tell where you are at.

Trad · Mar 25, 2010

Re: Planing Issues

I went home at noon and measered the cavitation plate. It is 2 to 3 inches below the center (v) of the boat. Could this have a lot to do with the planing issue?

hwsiii · Mar 25, 2010

Re: Planing Issues

Absolutely 100%.

H

steelespike · Mar 25, 2010

Re: Planing Issues

If it turns out to actually be 3" below I would wonder if they put a long shaft 20"on a short transom 15"You mentioned it was allready raised up some.

Trad · Mar 25, 2010

Re: Planing Issues

I just raised the outboard up as far as I can. The cavitation plate is still about 1/2" below the boat. I took the boat out and what a difference. I wish I could have raised it another inch. The motor looks funny with the clamps above the transom though. I measured the transom and it is indeed a little over 20". The outboard seems to be more than a 20", is that possible? I don't really know what else I can do. The motor sure doesn't have the get-up-and-go that my old 2 stroke had but the top end seems to be close. The dealer told me to expect this with a 4 stroke. Do you think the addition of a "Doel-Fin" would still help performance like my dealer told me?

Thanks in advance for all your help on this!

hwsiii · Mar 25, 2010

Re: Planing Issues

No, we need some pictures of the anti ventilation plate showing the bottom of the boat and a straight edge sticking out to the anti ventilation plate flat with the bottom of the boat. And also some pictures of where the engine bolts to the transom, from outside and inside the boat.

You might try reading this for a better understanding of changing props for better performance, and for the major differences between aluminum props and stainless steel.

http://forums.iboats.com/showthread.php?t=369057

They sold you the wrong shaft length motor for your boat, you should be able to make them fix this, free of charge as they knew it was the wrong motor when they sold it to you.

H

steelespike · Mar 26, 2010

Re: Planing Issues

Trad said:
I just raised the outboard up as far as I can. The cavitation plate is still about 1/2" below the boat. I took the boat out and what a difference. I wish I could have raised it another inch. The motor looks funny with the clamps above the transom though. I measured the transom and it is indeed a little over 20". The outboard seems to be more than a 20", is that possible? I don't really know what else I can do. The motor sure doesn't have the get-up-and-go that my old 2 stroke had but the top end seems to be close. The dealer told me to expect this with a 4 stroke. Do you think the addition of a "Doel-Fin" would still help performance like my dealer told me?

Thanks in advance for all your help on this!

Unfortunately the 4 stroke will tend to struggle more with the hole shot.
While the fin will help I prefer something like smart tabs.They will get you up and dampen any bounding around.The fin will put additional strain on the gearcase/antivent plate and a mount that may allready be taxed.Usually it is a fairly easy to raise a transom or you may be able to use a jack plate to gain more height and a finer adjustment,and some setback.
(gets the motor in cleaner water)

Planing Issues

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