Planing help w/ full load

[im faster]

first I own a 1993 S18fs (fish and ski) with a merc 115

Okay, so when it is just me and a friend taking the boat out no problem at all. however i have taken the boat out 2 other times with some more weight.
5 people this last time and it was difficult to get the boat to plane. (once planing i could reach about 10mph less than 2 person speed which is understandable)
In order to plane it worked best when i eased into it and it took 2-3 times as long when lightly loaded to get to plane.

SO....
When loaded heavy should I.....
1. have more weight in bow? to get it down or in the stern?
2. Are trim tabs a thing on such a small boat?
3. Upgrade to a larger motor(though i dont see this as much of an option money reasons)
4.???? any other advice?

 

[fordmugg]

What size prop? 3 or 4 blade?

 

[oldjeep]

Distribute the weight. If the 5 people are "bubba sized" then you are going to have to move them to the bow in an 18 ft boat.

 

[im faster]

3 blade quicksilver lazer2 prop

 

[im faster]

And everyone was 150 or less roughly

 

[spdracr39]

I had a boat that had trouble planing under load and I had to move everyone to the back till the bow was out of the water the when on plane they could go back up front. If this is going to be a common thing I would go to a 4 blade prop.

 

[im faster]

Okay, so a 4 blade will loose some speed and MPG but will get me out of the hole faster right?

 

[metriccrescentwrench]

My opinions:

Don't worry too much about 3 blade vs. 4 blade prop, you've got a more severe issue than that change could help. If you do anything drop down in pitch.

A 115 on an 18 ft. boat seems pretty marginal. What's the max size engine your boat is rated for? I know you said a bigger engine might be out of the question right now, which brings you back to looking at a lower pitched prop.

Also, do a compression check on your engine just to make sure that it's healthy. While you're doing that have a look at the spark plugs to see if one or two stand out as being much different than the others (and if so post photos in the Merc outboard section).

 

[im faster]

ill check into it.

 

[QC]

When loaded heavy should I.....
1. have more weight in bow? to get it down or in the stern?
2. Are trim tabs a thing on such a small boat?
3. Upgrade to a larger motor(though i dont see this as much of an option money reasons)
4.???? any other advice?

1) Move 1/2 the weight to the bow. Test. Depending on result, add and subtract bodies fore and aft.

2) Absolutely the best thing you could do to your boat if all else is right. You will NEVER be sorry about adding trim tabs to a v-hull boat unless you do it wrong. Helm adjustable tabs will change your boating experience forever. I am that confident, and no, I do not sell trim tabs...

3) You answered this already.

4) Investigate the relationship of pitch and RPM when discussing props. Read the sticky at the top of the prop section. Run one prop for light loads, and another for heavy loads.

I run a similar boat at times. It is not mine, so there are no tabs on her. I understand your dilemma very well, You just need to understand it, and adjust appropriately. I have planed the rig I am talking about with seven people on board. 18 foot Maxum with a 115 Merc 2 stroke, carbed.

 

[greenbush future]

boat is over 20 years old and depending how well this boat was cared for, it could have extra weight under the deck. You can check your foam for water saturation by doing a core sample, but you need to get to the bottom of the foam next to the hull to really tell if you are soggy or not. That can kill any boat's performance. I hate to see anyone spend $ before they fully know what is causing the issue.

 

[Scott Danforth]

+1 for moving people to the bow - I always had to do it in most marginally powered boats full of people
+1 on helm adjustable trim tabs - I added the Bennett 120 sport tabs to my SeaRay 190 and the experience was great

 

[im faster]

I replaced the floor last summer.

 

[airshot]

You should not have any problem planning out with 5 people on board, motor is not up to par or boat is water logged. My 18' alum hull with a 75hp had no problem with 5 adults, your 115 should not unless you have a problem.

 

[QC]

Different animals for sure. The one I drive will run 43 MPH with two people, but it struggles some with 5. Same motor and smaller fiberglass.

 

[roscoe]

What is a 1993 S18 ???
Glass or aluminum?
dry weight?
Wet weight?
Max hp rating?
2 stroke or 4 stroke?
Max rpm you hit when running with just one or 2 people on board?
rpm you hit when loaded with 5?

How long does it take to plane with 2 people, from the time you hit it, till the bow is down? 2 seconds, 8 seconds? 15 seconds?
How about when fully loaded?

Compression test results?

Chances are that a different prop will help, as will smart tabs, but you need to provide details first, so we fully understand what you are dealing with.

 

[Bubbasboat]

Distribute the weight. If the 5 people are "bubba sized" then you are going to have to move them to the bow in an 18 ft boat.

"bubba sized" Now that's funny!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:facepalm: