Need some advise on 4 stroke motors.

Ed L.

Ed L.

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I'm looking at a new rig and I do not have any experience with 4 stroke motors. It's not a big boat. 2015 Alumacraft Escape 165T with a 2015 25hp Mercury electric start with power T&T. Basically how do these new motors stack up today. Looking for the pros and cons. The boat is 2 hours away and I'm not sure I want to drive that far if said motor is not an adequate performer. I'm not looking for a speed demon but my expectations would be something that will put the boat on plane without having to add a fin of some kind. 25mph with me, 55lb dog a bag of decoys, shell box and a gun. Does that sound fair?
 
Ed,

Not familiar with that particular motor but according to the Alumacraft web site that boat weighs 646 lbs and has a max hp rating of a 50 hp tiller. Personally I don't think boats 'normally' need a motor as big as the max hp rating but I would wonder if a 25 is enough also. Guess I haven't added to your knowledge base but do share your concern.
 
I have a 2003 Merc 25 hp on my smokercraft that has a hull weight of around 225lb. With two guys and gear I run 25-26mph. I think the hull you are looking at will be underpowered if the hull weight is as much as indicated.
 
Ed,

Not familiar with that particular motor but according to the Alumacraft web site that boat weighs 646 lbs and has a max hp rating of a 50 hp tiller. Personally I don't think boats 'normally' need a motor as big as the max hp rating but I would wonder if a 25 is enough also. Guess I haven't added to your knowledge base but do share your concern.
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Thanks Pete. My thoughts as well With that weight in mind I've asked for a quote with a 40hp
 
I have a 2003 Merc 25 hp on my smokercraft that has a hull weight of around 225lb. With two guys and gear I run 25-26mph. I think the hull you are looking at will be underpowered if the hull weight is as much as indicated.
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Thanks Carl. With my old Cherokee 16' fishing boat with a 25hp OMC I imagine that was what I was getting as well. With the hull weight I'd be pushing it thinking I'd get 20mph.
 
I'm looking at a new rig and I do not have any experience with 4 stroke motors. It's not a big boat. 2015 Alumacraft Escape 165T with a 2015 25hp Mercury electric start with power T&T. Basically how do these new motors stack up today. Looking for the pros and cons. The boat is 2 hours away and I'm not sure I want to drive that far if said motor is not an adequate performer. I'm not looking for a speed demon but my expectations would be something that will put the boat on plane without having to add a fin of some kind. 25mph with me, 55lb dog a bag of decoys, shell box and a gun. Does that sound fair?
Ed I had a similar boat same size different manaufacturer with a 25hp Yamha 4 stoke without the power tilt and trim it was plenty fast I had originally had a 2 stroke motor on there I lost some top end but the 4 stroke gave more torque on the low end. It will get on plane with no issue there.
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Ed I had a similar boat same size different manaufacturer with a 25hp Yamha 4 stoke without the power tilt and trim it was plenty fast I had originally had a 2 stroke motor on there I lost some top end but the 4 stroke gave more torque on the low end. It will get on plane with no issue there.
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Thanks Larry. If I can get away with the 25hp it would sure save me a few grand in an up grade. I guess the thing to do is make the drive and take it for a test run.
 
Well it was bound to happen. Pete, I respectfully disagree with your take on max Hp., After having a couple boats that were not powered up to max I would never again do it again. Lots of reasons but you don't need to use all the power unless you need it. Motors are "happier" running at less than WFO. I plead ignorance on the 4 stroke though, maybe that changes things.
 
Here's something interesting a guy sent me. I was told marine architects use this calculation.


WOT (mph) = the sqare root of: (HP divided by weight (pounds)) times 175.

Example: 1800lb (Gross), 70hp, 5 degree deadrise.

70hp/1800lb = .038888, Square root = .1972, times 175 =34.5mph theoretical WOT.

With a flat bottom, use 200 rather than 175.
With a deeper deadrise, use 150 to 160.


I added 646=hull weight, 172=motor weight, 230=my weight, 50=fuel, 55=dog and another 50lbs for misc. for a total of 1203lbs.
Based on the calculations above the sq root of 25/1203 = 0.144157483.
0.144157483*175 = approx. 25.23mph
If this is true I'd be fine with that speed. Same load in my 14' flatbottom with a 25hp Yamaha GPS'd is 30mph. In that boat with a little chop and a crosswind can be a bit scary on the open Mississippi River.
 
Ed,

That boat sounds like it will weight somewhere close to mine and as you know I am running a 25HP. My boat is 17' x 64" and in its orignal confiiguration (meaning with console) was rated for 70HP.
 
Ed,

That boat sounds like it will weight somewhere close to mine and as you know I am running a 25HP. My boat is 17' x 64" and in its orignal confiiguration (meaning with console) was rated for 70HP.
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Mark,

I wondered if you were okay with the speed you get from your setup. I've only been in the boat once of twice.
 
Ed - I have an Alumacraft 1648 NCS and have a 15hp Nissan 4 stroke on mine. We are only running 2-3 foot of water so, I didn't need a 20 or 25hp. I love mine. It is fuel injected and has an electric start. It is very quiet and over the years has been extremely dependable. While not a speed demon, it always starts. It has made me a big fan of Nissan because of it's stellar performance. You are sure welcome to come over and try it out.


Just my 2 cents... Pat
 
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Its as fast as i want to go while holding a tiller....except when it doesn't start on the opening day of duck season....
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Yep....I guess I've been in you boat once when it was running! LOL..Kevin, If your referring to Marks motor it's an older 2 stroke Johnson. That particular day the fuel line split and the connector stayed on the motor but the hose did not! We were lucky and called for a ride from one of our party that was already at the blind

Thanks Pat. I had a Nissan 25hp electric start 2 stroke on a flat bottom when I lived in Florida. I agree they are a dependable motor. You don't see them up here very much.
 
First off I would try to do a test drive if you can. That will tell you more than anything. Secondly I agree with Tom I would put as much motor on the boat as you can afford and it will legally take.
 
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