New to boating and the forum

Phil33

Cadet
Joined
Jul 16, 2017
Messages
17
Just bought a 2010 Larson Fincraft 17sc it has a Mercury 4 stroke 60hp efi motor, propeller is a 10-13
Boat will not plane will only rev to 3300rpm and do 10 mph I talked to a prop shop and ordered a prop with a 9 pitch but I am wondering if there
Isn't another problem,motor and boat are like new only a little over 20 hours on it.
 

Stumpalump

Chief Petty Officer
Joined
Dec 5, 2013
Messages
413
Somthing is not right. Did you trim all the way down to take off? How many people were in the boat? Mine is an 18' with a 48 hp and
I spin a 17P prop at 5500 so I'm thinking being new to boating you either had too much weight in the wrong place or you forgot to trim down.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,583
Howdy

Post a pic of the stern showing how the motor sits in relation to the bottom of the hull
 

wahlejim

Master Chief Petty Officer
Joined
Jul 23, 2015
Messages
884
I would also get the boat weighed do rule out a worst case scenario, a water logged hull. Go to a truck scale, weigh the boat and trailer. launch the boat, weigh the trailer. See what you come up with. Minimal cost and sure beats throwing money at props and mechanics. The likelihood is minimal that a 2010 is water logged, but it wouldn't be the first time and at least you have piece of mind. Always good to know the boats weight for a variety of reasons.
 

Ned L

Commander
Joined
Sep 17, 2008
Messages
2,266
Something doesn't make sense. 'IF' the engine were way over-propped, (which would be keeping it from doing more than 3300 RPM), going to more pitch won't help.
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,657
Boat 1450#
plus motor, battery, gas, gear = 1900

Plus 450# of people = 2350#

Hull is rated for either 90 hp or 115 hp, depending on where you look online.

So motor is likely not big enough for the hull to operate efficiently.

YES, you have too much prop, a 9p will be closer.

And maybe a motor issue, like not firing on 1 cylinder.

Have you check to see if the flotation foam is waterlogged ? It could account for another couple hundred pounds of weight.
 
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Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
10x13 is very typical for that engine and would not be very far off for the given load. There is a significant weight issue, an engine issue or a control issue adjustment issue. I would not be spending money on a prop before all the other possibilities are eliminated.
 

Phil33

Cadet
Joined
Jul 16, 2017
Messages
17
Boated all day Saturday at Deer creek with new prop,it helped a lot was able to get to 5200 rpm and 21 mph gps it was pretty rough on the lake so might have done a little better in calm water. It is still sluggish takes 1 minute 10 seconds to get to full speed but I'm guessing that is because the motor is to small for the boat and weight.
 

Phil33

Cadet
Joined
Jul 16, 2017
Messages
17
Boat 1450#
plus motor, battery, gas, gear = 1900

Plus 450# of people = 2350#

Hull is rated for either 90 hp or 115 hp, depending on where you look online.

So motor is likely not big enough for the hull to operate efficiently.

YES, you have too much prop, a 9p will be closer.

And maybe a motor issue, like not firing on 1 cylinder.

Have you check to see if the flotation foam is waterlogged ? It could account for another couple hundred pounds of weight.
How would I check to see if foam is waterlogged?
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,545
Boated all day Saturday at Deer creek with new prop,it helped a lot was able to get to 5200 rpm and 21 mph gps it was pretty rough on the lake so might have done a little better in calm water. It is still sluggish takes 1 minute 10 seconds to get to full speed but I'm guessing that is because the motor is to small for the boat and weight.

What pitch? If 9 as suggested you got roughly a 2:1 improvement with a 30% change in prop pitch....yes 21 mph means you got up on plane {plane is defined as the boat on top of the water, with trailing water having moved away from the transom (transom is the vertical rear cross section of the boat) and forming a V out past the stern (stern is referring to the rear of the boat)}.

One minute ten seconds isn't all that bad considering your situation for a hole shot (hole shot defined as the time it takes to go from an idle in gear boat sitting essentially still, to the "on plane" condition defined above).

Now that you are on plane, don't expect such a drastic result from a slight change; won't happen....getting on plane is the big one.

Normally 200 rpm per inch of prop pitch change is a good rule of thumb. Don't have your engine specs but going to be 5500 or thereabouts so you have a little more to go and this will help your hole shot. Go on down to an 8 pitch and if you can't get that a 7. Your rpms should come on up but your speed may not; depends on lots of things. What you will get is better control in rough water, being able to stay on plane at a lower speed and not loose it and a faster hole shot. Engine will love you for it. Diameter of the prop will probably increase slightly with a pitch decrease but don't get hung up on that.....dia will remain "about" 10".

Once you get all that squared away and are out running best you can with your current "tucked in" trim position, start pushing it out, monitoring performance and how the boat responds until you find the "sweet spot" (sweet spot meaning that for any given throttle position, best speed/handling conditions) for that load, that day, those weather and wave conditions which will usually vary from outing to outing. Normally the smoother the water the farther you push it (the lower unit away from the transom) out, raising the bow, reducing the hull drag and in doing so, increasing your speed and rpms.

Last add some Sea Foam fuel treatment to your gas. Auto parts stores carry it and directions are on the can. It is well worth the money to keep it in your fuel. Will clean out any carbon that has built up over the life of the engine and engine will run stronger.
 
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roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,657
How would I check to see if foam is waterlogged?

That would require actually getting in under the floor and examining the foam.
Perhaps there is an access hole for the gas tank that would allow you to reach the foam at the bottom.

Congrats on getting it up on plane.
 
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