sponsons?

i have a boat that is rated for a forty horse engine and i have a fifty on it rear of boat sits very low in the water and i cant get it to plane out im new to boating and have had some people tell me that sponsons will help is there any truth to this

Re: sponsons?

Howdy, birddog.

Welcome to iboats.

If you have a boat that is 25% overpowered that won't plane you have a real problem. Sponsons would do you no good.

First of all, overpowering is a very bad idea. Consider going to a 40HP that is not sick.

Your boat is probably badly waterlogged and your 50HP engine might be better used as an anchor.

Tell us exactly what boat you have and exactly what engine. One or both need some extensive work.

Re: sponsons?

I would think even if the boat is waterlogged a 50 should get it on plane no? Considering it is overpowered and everything. Hopefully you're motor is just not running to it's full potential and you can fix it easily. If you're boat is indeed waterlogged, you're in for some good ol fun

Re: sponsons?

Don't assume it is necessarily overpowered just by the HP numbers... lets say its 1985 boat with a rating that is meant for prop HP. Now lets assume he stuck an old (1970's) merc classic 50 on it. That 50 hp engine doesn't put anywhere close to 50 at the prop when new, as the classic 50's were actually 45 at the flywheel., and it certainly doesn't put out 45 hp after 30 years.

In other words, if you use the non-common sense answer, a modern 40 hp 4 stroke would be fine, but an old 50 hp, (lighter and less power), is dangerous?

Re: sponsons?

This fantasy that pre-'85 outboard HP is somehow bogus has been around a long time. So has the notion that outboards automatically lose power as they age.

Both are wrong and are just yabuts for doing something you shouldn't do.

I agree that that 50 would probably dyno less than 50hp, but there is no reliable method for predicting exactly what it would dyno. Very unlikely to lose 20% in the drive train. If well maintained it might well dyno 50HP or more.

The point is that the boat is rated for 40HP, MAX. That means an outboard rated at 40HP or less.

Back to the OP's topic. Either the boat is not seaworthy or the outboard is very weak, or both. Either condition, or both, needs correction. Adding sponsons would be a bad idea.

Re: sponsons?

Just to add - sponsoons are generally part of the hull - either part of fiberglass or welded on aluminum. I can't picture adding them on after the fact and having them do any good for handling.

Also, even if you were to add them, it doesn't change the USCG max HP rating of the boat. I don't think an insurance company is going to care one bit about the additional sponsoons. I'd find a good trade for a tip-top shape 40 hp and enjoy it.

Re: sponsons?

The boat is a nineteen eighty five bass tracker 1 is fifteen foot long the engine has plenty of power in my opinion truthfully my problem could be as simple as me not knowing how to trim the motor properly

engine manufacturer is mercury and i beleive it is also an 85 model

Re: sponsons?

JB said:

This fantasy that pre-'85 outboard HP is somehow bogus has been around a long time.

Click to expand...

What is a fantasy about it?

Outboards were rated differently that's not fantasy it's truth.

Powerhead verse prop shaft are two different numbers.

Combine this with 4 strokes weighing so much more...

Sorry but these are truths not fantasy and not wrong JB, I fully understand your and iboats stance on overpowering but to say they are fantasy and wrong when the are completely true is just BS.

Re: sponsons?

Hulls are designed to run at certain speed ranges, and simply overpowering them typically offers little in terms of performance - unless you get into hull modifications. At that point, you become a boat designer/builder and begin working somewhere between theoretical hydrodynamics and good ol' fashioned grease monkey trial and error.

A 15' Bass Tracker is an aluminum hull. Not real beamy, but should be pretty light - if I've got it figured right. The difference between 40HP and 50HP on that boat should be noticeable, but not crazy. The 40 it's rated for should push it fine, and by extension the overpower should too. You've definitely got another problem going on. One of the boats I run is a 14' open fishing boat (3 bench with oars type) with a 9.9 HP and it planes no problem. You 15 has a bunch more weight, but not so much more than when I load three adults on my boat.