2stroke to 4 stroke weight?

[Cdm88]

I have a sears/sea nymph 14ft jon that came with a 15hp “gamefisher” 2 stroke. Ive been able to get it running fairly well but it still has trouble idling at times and died on the water once. Parts for this motor seem to be hard to come by. Im considering replacing with a 4 stroke but im concerned about the extra weight and how it will affect the boat. Will the transom support. 95lb motor etc. there is no info plate that i can find. any thoughts or guidance?

 

[MrGiggles]

It should handle it, however you may need to move the gas tank, battery, and any other heavy items forward to spread the weight out better. An extra 50lbs is not the end of the world, but in the wrong place, can make a huge difference in how the boat handles.

 

[FuzzyGrub]

I agree with Mr G. Some of us can remember when 2-strokes wern't all that light. A 1950's 25HP Johnson/Evinrude were pretty heavy. My 1963 10HP Sportwin weighed the same as my 1997 Nissan 18HP. I doesn't matter on the HP rating, just a slight hit to the overall capacity, the people, motor, and gear rating.

 

[jethro]

I'd be surprised if your 15hp 2 stroke wasn't already about 80 lbs but I may be wrong!

 

[airshot]

According to the owners manual, my 1994 evinrude 15 hp weighed 68 lbs dry, probably 75 lbs tops and it was a pull start.

 

[MrGiggles]

I agree with Mr G. Some of us can remember when 2-strokes wern't all that light. A 1950's 25HP Johnson/Evinrude were pretty heavy. My 1963 10HP Sportwin weighed the same as my 1997 Nissan 18HP. I doesn't matter on the HP rating, just a slight hit to the overall capacity, the people, motor, and gear rating.

I had an 83 25hp Johnson on a 14' Alumacraft. That motor was really chunky and big for a 25, shared the powerhead and stuff with a 35 if I remember correctly. The boat handled it fine, but porpoised badly without a hydrofoil.

 

[lckstckn2smknbrls]

I have a 105 pound 1983 25 hp Mariner (Yamaha) on a 1436 Wards SeaKing with no issues.

 

[MstrDan]

I had a 15 hp gamfisher myself. Got a 9.9 mercury to replace it. it weighs 98 lbs Difference in weight was about 20 lb. No problem for my 1967 14 foot FD Alumacraft. My back a different story! Love the 4 cycle

 

[airshot]

I agree with Mr G. Some of us can remember when 2-strokes wern't all that light. A 1950's 25HP Johnson/Evinrude were pretty heavy. My 1963 10HP Sportwin weighed the same as my 1997 Nissan 18HP. I doesn't matter on the HP rating, just a slight hit to the overall capacity, the people, motor, and gear rating.

That was back in the day when they were built like tanks, everything was metal and beefy. No plastics hardly and hoods were thick and heavy, they took a beating. I had a 1952 Sea King 5 hp with the heavy aluminum screw on cover, it rolled off the back of a trailer and dropped onto concrete, mabey 4' up....just a scratch in the paint, no dents!!! Woyld like to see what would happen to a new one if it was dropped 4' onto concrete ??

 

[FuzzyGrub]

Somehow I knew, I wasn't the only one that remembered those days.

 

[thill]

I had a 15 Gamefisher, and that thing was LIGHT, on the order of 55 lbs. I dont' think it weighed as much as a bucket of drywall mud. The newer 9.9 merc I installed for a friend recently was a BEAST, well over 100 lbs. Enough to make you grunt when you lift it.

I just sold a 12' Lowe with a 9.9 Mercury from the 70's, and that was a light little motor, too, but not as light as that Gamefisher. Very nice balance on that boat, and it pushed it well.

 

[beagle]

Out of the current crop of manufacturers, Suzuki seems to be the lightweights of the group. A new Suzuki 15hp short shaft is listed at 97 pounds. and "generally speaking" the Gamefisher 15hp is listed at 65 pounds. It's less than (1) full 6 gallon tank of fuel difference. I don't have personal experience with fuel economy but I suspect the four stroke will be noticeably easier on fuel than the two stroke and most likely quiter by another noticeable margin and come with a decent warranty. On the downside, I've never had a four stroke of comparable power put out the midrange beans that my two strokes did.

I love old two strokes but I hate paddling. They smell like money to me.

I was flipping through various King Fisher boats on iboats .com (Ed: can I post a link here? Sorry if that's a no no, please remove with my apologies) and they're quoting a 20hp hp max. The 20-35 hp Johnson/Evinrudes come in around 125 pounds so you would be within the weight area they rated it for with just about any modern 15hp. I think the HP ratings were as much about engine weight as they were transom HP capabilities.

 

[thill]

By the way... I recently tested a 15 HP 4-stroke Mercury on the same 1996 Lowe 1248 mentioned above.

The owner ran a rowing school, and having the motor run well could mean life or death. They sometimes had kids flip boats, or get too close to the rapids, and they needed a reliable engine to do rescues. This meant that I had to thoroughly water test the engine after repair.

Since the 15 uses the same block as the 9.9, I figured it would be fine on the 1248. The Lowe was rated for 9.9 HP and 3 people.

The motor was considerably bigger, but it looked good on the boat:


I dropped the boat in, and noticed that the nose sat pretty high, but didn't pay attention to how low the back was. (Lesson learned) It looked fine, looking down at it:


Notice that I had put the battery and fuel tank as far forward and the cable and hose would allow. I thought that would give it deent balance to offset the heavier motor.

But I was wrong.

Right after that picture was taken, I stepped in the boat, onto the back bunk. The back corner of the boat dipped below the surface and about five gallons of water jumped in instantly. Shocked, I jumped to the front of the boat, and then back up onto the dock. That was a close one! A few more seconds and that boat would have gone down.

I used a minnow bucket and dipped the water while laying down on the dock. I pulled the fuel tank forward and then tried to see if sitting in the middle bunk and reaching back to control the motor would work.

It seemed better, so I putted around in a circle, but anytime I gave it any throttle, the back would squat almost to the surface, and I would back off quickly. Could not get it up on plane safely. No tiller extension made it too dicey.

If I could have moved the battery and fuel well forward, plus an extension handle on the tiller, I think it would have been okay, but I didn't have any extensions with me. I loaded the boat up and got out of there, REALLY glad I didn't sink the boat.

I ended up testing the motor on a 16' boat, and it ran great, no issues. The problem had been a perforated diaphragm @ the accelerator pump of the carb flooding the motor. So a kid would flip a boat, and the instructor cou

If you go with a 4 stroke, be careful until you find the balance of the boat. If your boat has a 20" transom, you will probably be fine, but test carefully first.

 

[FuzzyGrub]

By the way... I recently tested a 15 HP 4-stroke Mercury on the same 1996 Lowe 1248 mentioned above.

The owner ran a rowing school, and having the motor run well could mean life or death. They sometimes had kids flip boats, or get too close to the rapids, and they needed a reliable engine to do rescues. This meant that I had to thoroughly water test the engine after repair.

Since the 15 uses the same block as the 9.9, I figured it would be fine on the 1248. The Lowe was rated for 9.9 HP and 3 people.

The motor was considerably bigger, but it looked good on the boat:
View attachment 114054

I dropped the boat in, and noticed that the nose sat pretty high, but didn't pay attention to how low the back was. (Lesson learned) It looked fine, looking down at it:
View attachment 114055

Notice that I had put the battery and fuel tank as far forward and the cable and hose would allow. I thought that would give it deent balance to offset the heavier motor.

But I was wrong.

Right after that picture was taken, I stepped in the boat, onto the back bunk. The back corner of the boat dipped below the surface and about five gallons of water jumped in instantly. Shocked, I jumped to the front of the boat, and then back up onto the dock. That was a close one! A few more seconds and that boat would have gone down.

I used a minnow bucket and dipped the water while laying down on the dock. I pulled the fuel tank forward and then tried to see if sitting in the middle bunk and reaching back to control the motor would work.

It seemed better, so I putted around in a circle, but anytime I gave it any throttle, the back would squat almost to the surface, and I would back off quickly. Could not get it up on plane safely. No tiller extension made it too dicey.

If I could have moved the battery and fuel well forward, plus an extension handle on the tiller, I think it would have been okay, but I didn't have any extensions with me. I loaded the boat up and got out of there, REALLY glad I didn't sink the boat.

I ended up testing the motor on a 16' boat, and it ran great, no issues. The problem had been a perforated diaphragm @ the accelerator pump of the carb flooding the motor. So a kid would flip a boat, and the instructor cou

If you go with a 4 stroke, be careful until you find the balance of the boat. If your boat has a 20" transom, you will probably be fine, but test carefully first.

FWIW: I have a very similar boat. A 14' fishmaster. Max motor was 15hp, but forgot the capacity numbers. I wouldn't recommend stepping into the boat on to the rear bench with any motor on the transom. It is easy to put the corner under. This is the boat I ran the '63 10HP and '97 18HP on. I had a 6gal tank that was just infront of middle bench and group 29 battery just behind the front bench. That worked well.

I tried the extended trottle handle operating from middle bench but couldn't get comfortable with it. Too far away from shift lever and to quickly raise onto motor into shallow mode. A camp neighbor has a similar boat and he always runs from middle bench. A little 5hp 4-stroke Merc, and planes it out easily.

 

[sonny1]

Good info.

 

[sonny1]

Just measured the transom on a lonestar 14 foot it is 16 inches.

 

[Ron68]

Once you decide what you're going to mount I'll still need to find a neutral balance if possible like has been stated.
With you and all your gear and fuel and new motor, setup the weight so the boat is as neutral as possible at rest not running.

 

[sonny1]

That means I am definitely going on a strict diet and workout routine after surgery.

 

[airshot]

With that short transom, you might consider fabricating a splash well to keep water from comming in. Not that hard to do with some sheet aluminum.

 

[Crazyboat]

I have a sears/sea nymph 14ft jon that came with a 15hp “gamefisher” 2 stroke. Ive been able to get it running fairly well but it still has trouble idling at times and died on the water once. Parts for this motor seem to be hard to come by. Im considering replacing with a 4 stroke but im concerned about the extra weight and how it will affect the boat. Will the transom support. 95lb motor etc. there is no info plate that i can find. any thoughts or guidance?

I had a 15 long shaft Johnson weight was 87 lbs plus 10 pounds of wood used to beef up the transom, now I was a kid and light myself, but the boat was only 12' long and weight was only 80 pounds for the hull, I think you'll be fine. If you're not sure, drop her in the water with the current set up and drop in the fuel take in the rear to approximate the weight.