Alumacraft Fisherman 145 with 25 HP Merc only goes 11 MPH?

[karl7feet]

Everyone,

I just purchased a new Alumacraft Fisherman 145CS with a new 25 HP Mercury 4 stroke F25 ELPT motor, and when I put my family in the boat (two adults and two kids (700 lbs total)), the boat would only go 8-9 mph. I took the boat back to Cabelas and told them what happened, and they took the boat out with a couple of guys weighing about 400 lbs, and they said they got the boat to 23 or 21, it depended on what prop they had on it. From talking with them I found out that I needed to have the motor all the way trimmed in against the boat, and I probably did have it trimmed out a bit. I am new to boating and did not realize the importance of the trim adjustment on the speed, lesson learned.

So I get the boat back and take my family out for another test run, this time with the motor trimmed all the way in against the boat, and the first time we take it out, it slowly creeps up to 21 MPH, and I do mean creeps. Like from 11 mph to 21 mph, took about 10 seconds for every 1 mph. This was on calm water with no wind.

Then we try doing it again and can only get up to 11 mph. My wife had switched seating positions with our two kids, but I was still driving (270 lbs), and my wife and kids were moving to different positions in the boat, but not the front casting platform seat.

The Alumacraft brochure says Capacity: Max persons/weight is 4/925. The motor says it weighs 180 lbs, so adding that and the trolling motor, gas, oil, fishfinder, probably gets us up to the 925 or slightly over.

Being new to boating I really did not expect to have this issue with the boat only going 11 mph. I thought it would get up on plane at about 20 mph or so, and that would be fine. Not looking for any speed records, just a boat to go fishing on with my family and kids. But 11 mph just feels wrong. It was great when I just went out with one of my kids and got going up to the low 20's at a decent rate of acceleration. But with the whole family at 11 mph it is just anemic.

I will go talk with Cabelas again and see what we can do. Does anybody have any suggestions about the situation? Is this typical performance when you are right up to the boats weight limits? Would having a different prop or getting the 30 hp motor make that much difference?

Thanks for any suggestions!

 

[steelespike]

Re: Alumacraft Fisherman 145 with 25 HP Merc only goes 11 MPH?

Is the boat setup as a tiller?What size prop is on it now?Number appears near the base of the blades or under the prop nut.
Yes planing will be difficult.Generally small 4 strokes have a difficult time dealing with a load and need to be setup carefully.You really need a prop that gets your motor near the top of its rpm rating.( 6,000)with your typical load.You need to put more weight forward at least till you get on plane.Wife all the way in the bow,kids on the edge of the forward platform and lean your 270 lbs as far forward as your reach will allow.Once it planes adjust the weight if the bow seems too heavy.The motor needs to be setup using a tach.in order to determine the right prop.Setting up without a tach is like selecting a prop in the dark.

 

[karl7feet]

Re: Alumacraft Fisherman 145 with 25 HP Merc only goes 11 MPH?

The prop numbers are 9.75 x 9.5P, which is one of the recommended prop sizes on the Mercury prop selector site, and it is a console model.

I went to Cabelas today and talked with the gentleman that sold me the boat and he said he needs to talk with the mechanics about the prop selection, and whether that will fix the problem, or whether we need to go up to the 30 HP motor.

So moving the weight around from the middle to the front would help that much?

Does anybody think changing the prop to a 9.5 x 11, the other recommended size on the Mercury website, would do the trick?

Would getting the 30 HP motor be the most likely solution to this?

Thanks for your input. I never thought just getting the boat to plane would be such a big deal, but apparently with this size engine/boat it is.

 

[Silvertip]

Re: Alumacraft Fisherman 145 with 25 HP Merc only goes 11 MPH?

Going from a 9 x 9 prop to a 9 x 11 prop will make the problem worse, not better. Yes -- shifting the load around makes a big difference in boat handling. If this engine is not yet broken in, you might wait until that time period passes before making any prop changes. I assume you also had about 6 gallons of fuel in this boat (about 50 pounds), life jackets for everyone. Perhaps some drinks, fishing tackle, anchors, etc. You would be amazed at how quickly this stuff adds up. Next test, leave the kids at home and just you and your significant other go for a spin. I think you will find the boat needs a bigger engine. What does the maximum HP capacity plate say?

Edit: As I suspected -- that boat is rated for a 40 HP max. Your 25 HP engine is 60% of the max rated HP. General rule of thumb is to power a boat with a minimum of 70 - 75% of rated HP for average performance. Power it at the maximum for optimum performance. While you may have thought the 25 would be sufficient, you might be surprised to learn that the 40 might be more economical to run than the 25. Why? Because the 25 has to run wide open to get anywhere whereas the 40 would be loafing at probably about 1/2 throttle on that boat. This is the problem with most package boat deals. The power them for the price point -- not reasonable performance.

 

[steelespike]

Re: Alumacraft Fisherman 145 with 25 HP Merc only goes 11 MPH?

My info says the boat is rated at 30hp. The boat is overpowered by the weight. compounded by the small motor.We have a 18ft Crestliner bare bones utility 375lbs originally a 25hp Gale it would plane with 4 to 6 adults with no special prop selection.The larger footprint of the 18 gets up on the water easier. I think you can see a bare 18 is about 1/2 the weight of your boat with a much bigger planing surface.
With you at the console try it with the wife at the bow and the kids near you or slightly ahead.
The idea is to get it planed and then try to lighten the bow slightly so it stays planed but doesn't plow. It will be a struggle.A 30 might plane a little easier but the weight still over powers the boat. In my opinion the 25 would do a lot better on the VS or TS 16 tiller
again about 1/2 the weight of your fisherman with a bigger planing surface.And it might even cost less .Not as fancy but more room and more speed.

 

[karl7feet]

Re: Alumacraft Fisherman 145 with 25 HP Merc only goes 11 MPH?

The maximum HP for the Alumacraft Fisherman 145 CS is 30 HP, so getting the 40 HP is not feasible.

If Silvertip is correct when he says that changing the prop to a 9 x 11 would make the problem worse, then it looks like the only solutions are to put the 30 HP motor on it and to get the family used to shifting initially forward, and then back once on plane, when we have the whole family on the boat. The performance was fine when it was just myself and my 100 pound son.

Can someone confirm that changing the prop to the 9.5 x 11 would make the problem worse?

When we did these two "maiden voyages" it was just the four of us (700 lbs), our lifejackets, 5 gallons of gas (5 gal x 6 lbs/gal = 30 lbs), two batteries, trolling motor, two bumpers and fishfinder. No rods, food, anchors or anything else.

Thank you everyone for your input. It helps someone that is unfamiliar with boating to understand how this all works! Additional comments are always welcome.

 

[steelespike]

Re: Alumacraft Fisherman 145 with 25 HP Merc only goes 11 MPH?

There is no question an 11" pitch would make the problem worse. There are 3 other load props available here at I boats a 9",8 3/10 and an 8. They must be available to your dealer as well.
Because the calculator says 9 1/2" doesn't mean its the only size that will work.
It appears the 9 1/2 is not quite there a 9 likely would work.
The easier for the motor to plane the easier to adjust the balance once you get on plane.
It would be interesting to see what the boat does with just you aboard.
I found a 25 Evindude Etec test on an 18ft Sea Ark 1100lbs dry 2 people(420lb) 25 gal fuel and gear made 19 mph Probably one more would make planing hard.Found a Etec25 on a bare bones Alumacraft V16 280lbs,(The boat you should have).2 men,6 gal fuel and gear 31 mph.Alsofound a 30Etec on a 570 lb 16ft Starcraft 220 lb driver,6 gal fuel and gear.over 27 mph. Unfortunately not Merc tests but should give an idea what a 25/30 can do set up right.
Its not unusual to have to move people to plane easier its not unusual for certain 300 hp boats to require a weight shift to make it easier to plane.

 

[karl7feet]

Re: Alumacraft Fisherman 145 with 25 HP Merc only goes 11 MPH?

Well everyone, we ended up swapping out the 25 HP motor for the 30 HP motor and all is well now. Cabela's in Lacey, WA allowed us to swap the 25 hP for the 30 HP motor for the difference in price ($630) and now the boat planes with all four members of our family easily and we are happy with its performance. All is well. I would recommend to anyone buying this boat to get the 30 HP motor. When my 8 year old son and I (370 lbs) are in the boat we top out at 25 MPH. I think we got to about 23 MPH when the whole family was in the boat. Thanks to everyone for helping me out on this issue. Hope this thread will help someone that is considering this boat/motor combination.