Two to Four stroke conversion questions

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beerkeg

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I just bought a 16' Mirrocraft Lake Fisherman, its a super wide, extra deep side console aluminum boat. The Coast Guard plate says its rated for up to 50hp. It currently has a 1978 manual start remote control Johnson 35hp on it. The motor on it runs fine but I'm not a fan of mixing gas. The 35hp weighs in at about 122 lbs on the hook.
I got a deal on a 35hp Honda with power tilt/trim and electric start which will work with this boat, but it weighs in at 223 lbs hanging on a hook in my garage.
My question is will the added weight be a big issue? What concerns me is that the 35hp Honda Four stroke weighs more than the heaviest two stroke available when the boat was new in 1978. The transom is solid, no rot issues. The side console is also towards the rear of the boat, so my weight, about 375 lbs, plus the battery, fuel tank, and motor will all be at the back of the boat. Its an open boat with split bench seats so there's not many options when it comes to moving the fuel tank and battery around either. Does the Honda sound like it'll be too heavy?
My goal is to not have to pull start the engine, the thing is hard to pull and hard to reach since I have to step over the only full width bench seat in the boat to get to the motor.
The other option is to just add a starter to the 35hp two stroke and deal with the fuel mixing but I really like the idea of a four stroke.
If the 35 Honda sounds too heavy, what would be the largest four stroke I can hang?
 

Sea Rider

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What's the max weight that transom can hold ? is it possible to shift center console, battery bit further to compensate added transom weight ? Post combo pics to have a look..

Happy Boating
 

Chris1956

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Gee, how does the boat sit when you stand next to the current motor. If the boat is near swamp, I submit that the 100# heavier 4 cycle motor will be too heavy. If she hardly changes trim when you stand there, the new motor will work fine....

Simple test.....
 

Scott Danforth

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move the battery up front, upsize the battery cables accordingly, move the cooler from the back, to forward a bit. mount the motor and go boating. the extra 100# wont affect much.
 

Sea Rider

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Worse scenario : if the boat tends to dramatically rise bow up while trying to plane, trim it down beforehand a bit, go full throttle and once on plane trim it bit upwards to maintain proper plane. A prop maximization if in need to pull wot revs higher to plane combo faster along deck weight well distributed is a must consider.

Happy Boating
 

flyingscott

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Your 35 Honda is only 40# heavier than the 1978 50 hp motor your boat could have come with.
 

beerkeg

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When I walk to the back of the boat know, its fine, its got a 20" transom and when free floating with no one aboard, its got a foot of transom out of the water. I put the battery and 6 gallon gas tank towards the port side to offset my weight.
Putting the battery up front may be a problem, the boat has no floor, its just an open hull. It measures 16" long with an 84" beam width. Its got three bench seats, the rear bench goes all the way across, the middle bench is split, with the console on the right half of that bench, and the front bench is split. There's a short closed bow area, about 20" but it only covers the tip of the bow area. There's no flat area below to set a battery. There's also no place to hide or run cables. As is it the side console has a steering cable that runs down the right rear, along with two shift cables and a kill switch wire. I'm basically sitting at the right rear of the boat on the rear bench seat, with the console ahead of me on the middle bench. The console sort of reaches rearward off that middle bench seat so it can be reached by the driver.

There are two flotation boxes on each side in the rear, they make the rear bench form a U shape with an opening in the middle between the seats and the transom. There's a bilge pump, fuel tank and battery in this area. There are folding seats for the driver and passenger, side by side on that rear bench.

One of the reasons I bought this boat was that my 14' boat was too small and couldn't take the weight of two guys and a 25hp motor. With its 15" transom, it was near swamping at rest with just the motor and two people in the boat. The gunwales would nearly roll beneath the water every time I landed a fish. This hull is very stable. I've been safely able to haul two people and a dozen crab pots and a days catch without any worries. The open center area makes moving around a lot easier.
Power and speed wise, 35hp is fine, the boat planes easily and has plenty of speed for where I run.
I have a seized up 35hp parts motor here with a good starter and bracket, I suppose I could just bolt that onto this motor and run a starter button somewhere, it don't have a charging system, but I only start and stop the boat half dozen times each day when I'm out and the battery gets charged when I get home. The size 27 deep cycle should have plenty of power for this.

Besides the Honda 35hp, I have a 1989 Evinrude 50hp two stroke here in real nice shape but my concern with that was that it would use more fuel, and not only add more motor weight but require me to carry a lot more fuel. With the 35hp, I can run all day on one 6 gallon portable tank and I keep a 3 gallon up front as a back up if needed. I've only needed the 3 gallon once and that was the day I brought the boat home. The old owner and I took the boat out fishing for the day, ran it all over the area where I bought it, plus I gave it a good workout to see how it handled, then I drove the boat from the ramp where he launched the boat with his trailer to another ramp where I had someone waiting with a new trailer about 30 miles away. I didn't run it out of gas but it was close to running the 6 gallon tank dry that day, I switched tanks about 10 miles from the marina where I was heading. Since then, its never burned more than 5 gallons in a day.

The 50hp was a bit hard on gas when it was on my Starcraft Super Sport, but that was a heavier boat by a few hundred pounds or so. I'd burn 8 to 10 gallons in a day on the water in that boat with the 50hp. The 50hp OMC also doesn't have tilt & trim..
The fact that the Honda has tilt and trim, plus the fact its likely to burn a lot less fuel was the main idea, along with not having to mix gas anymore.

The 35hp OMC is a good match for the boat size wise, both in hp and weight, What I'm afraid of is that adding the extra weight of the Honda, or even the 50hp OMC would offset most if not all the hp gains in lost fuel economy and freeboard. I don't want a boat that's barely afloat at rest, I've been there before and its no fun. I had a similar boat with a 135hp on it about 30 years ago, although that boat had no battery or electric start to deal with. It was fast but it was never more than 3" from swamping with that motor. If I pushed it off the beach on the lake too fast it would take water over the transom. Adding my weight at the stern on the tiller made it downright dangerous but it was fast. Once it was up on plane it flew across the top of the water but taking off was a little scary, The prop wash during a full throttle take off would evacuate all the water from beneath the boat and the hull would sink beneath the surrounding swell of water before it moved forward. I suppose if you were to have backed out of the throttle at that point the boat would have swamped.
That boat is what turned me onto these hulls, that boat was a bit longer and a few years older than the one I've got now and without the split bench options but the abuse it stood up to back then really amazed me. It was old enough not to have a HP or weight placard on it but all in all it took that 35hp well. I have no idea what top speed was but it was scary fast.

40 years later I'm a bit more cautious, I have no interest in speed but I hate a boat that won't get on plane or one that isn't balanced right.

I do see a few of these on the water here with older 50hp Mercury motors on them, and they seem to handle that just fine. Who ever sold these must have been outfitting these with Mercury motors back then. Mine supposedly came new with the OMC 35hp though. There are no holes drilled in the transom, so my options are open when it comes to fitting another motor.
 

QBhoy

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I wouldn’t advise it at all. Try and get a late model 50hp 2 stroke yamaha if anything. Save you money too.
 

roscoe

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Just slap tha Honda on there and go for a run.

Worst case scenario is you have to find something else.

It has several things going for it.

Its a Honda
has t n t
is a 4 stroke
electric start
its a Honda

If you need to, you could easily mount a battery box to the front side of port center seat, and run the cables down the port side in an electrical conduit.
 

82rude

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Put your 50 evinrude on the back,the diff in gas usage will be minimal.Theres no rule or law that says you have to use the 50 at full power ,but it sure would come in handy in certain situations.
 

Scott Danforth

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grew up with a 50hp merc on the back of a 14' Mirro ski-n-troll. not sure there was anything except WOT. a 50hp on the 16' would be my recommendation if you have one.
 

QBhoy

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grew up with a 50hp merc on the back of a 14' Mirro ski-n-troll. not sure there was anything except WOT. a 50hp on the 16' would be my recommendation if you have one.

Totally agree. I introduced my friend to boating years ago with a wee 13ft fletcher speedboat with a classic 50 Merc 4 cylinder on the back (actually 45hp for some reason). He has no mechanical sympathy at all. The throttle was like a switch to him. Either off or on.
He didn’t even pay much attention to the exact oil mix. It was the most reliable wee thing I’ve ever seen. Was punished most weekends for years and never missed a beat.
He has since managed to break every other engine he has had.
Who needs timing belts and valves to worry about on an outboard ? Get a good 2 stroke and enjoy boating.
 

beerkeg

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Considering the weight, I guess a 2 stroke is the only option but I've steered away from old Mercs lately after having a half dozen or so of those 50's with the shaft rusted into the crank splines. I've got a 35hp sitting here now like that.

The OMC 35 on it moves it along just fine, a buddy has the same boat with a 15 Merc 4 stroke on it and his does fine with that with two big guys but its not fast by any means. I never checked the speed but on a crowded narrow river with a no wake zone every 100ft there's not much use for a bigger motor. For now I'll just add a starter and button off the parts motor. If I knew the stator and charging system was a dead swap between the rope start model and the remote control model I'd swap that over too. The motor on it runs great, it starts first pull but that first pull almost yanks my knuckles out of their sockets.

I've blown up a few 50hp OMC motors over the years, not sure what happened but they broke lower rods at the wrist pin. On the last one I was running along at about 5300 RPM, just about max throttle on a 15' boat with an '85 60hp twin, I had owned that motor for three or four years without incident and the fuel pump, and water pump were fresh that spring. While running along on open water I heard the motor change pitch a bit, it didn't rev up, it got throatier sounding. I backed off the throttle turned for home not wanting to get too far out and have an issue. I hadn't heard it make any unusual noises before so I figured I'd best go home and take a look. At the time I was thinking maybe the lower exhaust tube had cracked or worked loose somehow. It ran fine back to the dock, I tied it off and went to get the truck. When I went to restart the engine, it wouldn't crank, it never budged. After having to get in the water and hand load the boat I brought it home and pulled the head. The lower cylinder had a rod bolt laying in front of the pistion, the head was beaten to pieces, and the piston was floating free. I was able to grab hold of one of the bits stuck in the piston and pull it out, as it came out, it fell in three pieces. The odd part is that it never made any noise that I would have thought was a rod knock or piston hitting something, it just got louder, like a lawn mower without a muffler.
The engine was a total loss. I swapped it out for a good used 50hp I had and ran it for another few seasons. I took that 50hp and put it on an aluminum flat bottom boat, re-propped it and replaced the water pump and ran it for a year, it too lost the bottom cylinder while running at speed, only that time it just flew apart. The lower rod broke, the piston smashed into the head so hard it cracked the head and popped off two bolt heads. The sudden stop snapped off the flywheel and twisted the driveshaft splines. I was running at about 4,000 rpm in deep water on a lake when it blew. I swapped that motor for a 70hp. Two years later, this time with a much newer 1991 40hp on a 14' MFG, I was running along at full throttle, the motor had fairly low hours and it was converted to 50:1 premix. The motor bucked a few times, it acted like it lost spark for a second or two then cleared up. I backed off the throttle, it idled fine, revved up fine, so I continued back to the dock. About 400 yds from the dock, it bogged down and died. When I tried to restart it, it sounded like a coffee grinder chewing up bolts. I drifted back to the dock, loaded the boat and attempted to tear that one apart. When I found the block ripped open behind the starter and the flywheel spinning freely without the pistons moving, I just pulled the power head and stripped it for parts. What ever failed broke the crank and smashed the block.
I had the same thing happen to a later 40hp Merc Twin.

Now, with all that said, I've been running a 1966 33hp on my 14' boat now for 30 years, it never misses a beat.
I've also got a Gale 40hp, about a 1962 or so that's run perfect since the day I bought it at a yard sale for $50 back in 1979. It ain't pretty but it runs great. Its a lot easier to pull start than this 35hp I've got on this boat though. It spins over like there's no compression but it runs fantastic.

I've got several very clean lower hours 50hp motors here now, all OMC, that I can try if needed, but for now the 35hp will get a starter I guess.
 

racerone

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I guess there is a reason why those $ 50 yard sale motors are available.----Usually junk when you get them.-----The occasional one might be a " lasting success " I suppose.
 
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That old Gale 40, has a compression release when you pull the starter cord, that was a feature that came out on the 1957 Johnson 35's
 

GA_Boater

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That old Gale 40, has a compression release when you pull the starter cord, that was a feature that came out on the 1957 Johnson 35's

For the second time - Stop posting in old threads!

And read the thread before posting.
 
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