Mirrocraft max hp?

[freeisforme]

I picked up a Mirrocraft the other day which has a rope start only 1979 Johnson 35hp on it, the boat moves well with the 35hp, at least it did with just me and the guy who I bought it from in it. The motor is a real bear to pull start though, the compression feels super high and although it starts on the first or second pull, it kills my hands and takes all of my weight to get it going.
I have a good running same year 55hp with electric start and was wondering if this hull can handle the larger motor?
There's no rating plate and the original HIN has been replaced with a state issued number, which many boats here have. The hull is marked
Mirrocraft Lake Fisherman, it measures 16ft 7in long down the middle< (Top if the transom to the tip of the bow), and 84" across the widest point of the gunwales. Its a bench seat type hull with a step through middle seat and side console atop the middle half seat on the right, with the driver's seat mounted on the rear seat bench.
I did consider just changing the flywheel, and adding a starter and bracket but it doesn't have the means to charge a battery either, and I'd like to ad some basic lights too.

 

[flatheadsteve]

http://boatspecs.iboats.com/Mirrocraft_by_Northport__3616-20_16_Lake_Fisherman__1987/bp/66b57484
Sounds like your boat and says it's rated for a 60hp...keep in mind that's for a 2 stroke which is lighter.
Edit to add mirrocraft still makes the lake fisherman 2 but with a 74" Beam and rated for a 30hp.

 

[freeisforme]

The closest I could find in their old brochures is from 1978, but the measurements don't match exactly.
I'm measuring from the tip of the bow across the top to the back of the transom, and I get 16ft 7in. At the widest part of the gunwales, across the top at about the area of the front bench seat is 84".
The '78 brochure shows only a 16ft 2in hull with a 72" beam. The decals match 1978, as does the color.
None of the 70's models list a split middle bench though. The semi closed bow is similar though, as is the console in the '78 brochure.
In 1978 is says 50hp max for the listed boat which they call their 'flagship' model.

https://boatbrochure.com/cdn/shop/products/30384_03.jpg?v=1571273673

 

[Crazyboat]

http://boatspecs.iboats.com/Mirrocraft_by_Northport__3616-20_16_Lake_Fisherman_III__1985/bp/66b57486
IDK what the differences might be between your boat and this, but it calls for a 60 Max.

 

[freeisforme]

It was dark by the time I got home but here's what I'm seeing for the measurements.
The motor is newer than I thought, (J35RLCTS, making it a 1983 but still a 35hp).
The boat is open hull, no floor, and just two folding seats and a side console. Its light but
I'd guess its more than the 550 listed for the newer boats. They did make these in a full
bench model with no side console too.

The side of the boat has a plastic Mirrocraft emblem on each side near the transom, and
"Lake Fisherman 17" on each side.
A buddy has the 16ft version and it measures 16ft 2in long but his a floor, but a solid center bench seat
and a shorter bow plate up front. The open 16ft actually has more room but measures only 72" wide.
His rating plate is 40hp max, but that boat has a 15" transom. His is titled as a 1986 and he bought it new himself.

Either way, even if its only rated for a 40hp, the 40, 50, 55, and 60hp OMC twins all weigh the same. The difference between them is minimal. I had a 40hp on an early 60's Ski King years ago, and upgraded to a then new 50hp in 1989, and all I gained was 3 mph in top speed. The acceleration increase was hard to even detect if there was any at all. I still have that 50hp as well, but its a short shaft and would need some work to use it on this boat. I do have a same year 40hp in a long shaft, and I could swap the power heads and run that but the 55hp I have here is low hours and turn key. The newer 50hp is likely lighter though due to the smaller lower unit and lighter engine bracket.
I also am not a fan of the hydraulic tilt mechanism on the newer motors, they seem to always be an issue on used motors.

 

[beagle]

Sounds almost like asking permission and I'm the probably the wrong guy to ask if it's okay to put more HP on a transom. Legally, and this is strictly informational as I'm not a boat builder, but I found some USCG documentation on maximum HP calculation at
https://www.law.cornell.edu/cfr/text/33/183.53
55hp is about half of what that calculation came up with for a 16' x 7' wide 20" transom remote steer. That's a big boat (in my eyes) with (I think I saw) three knee braces and I'd have zero problems putting it on there. It's what, about 45 pounds or so heavier than the 35? Change a trolling battery to a Lithium and it's a wash. Even going from the 2cylinder 45 cubic inch 55 to the three cylinder 49 cubic inch 55, and the extra 40 ish pounds it has over the two cylinder, I don't think I would get too wound up about it on a tall boat with a 7 foot beam and a bunch of transom bracing. Most of the information I could find on that vintage Mirrocraft listed the 84" wide boats at 18 feet and 90ish HP. How thick is the transom on this boat?

My real concern would be how it handled and whether I could put someone with no seat time behind the wheel. I'm guessing you should be able to. Some folks can break a bowling ball in a sand box, and a 15 would be too much. Some folks can drive a Corvette forever and never get a speeding ticket. Their new stuff shows some 7' wide boats at 16'9" and 90hp... I'd email some pictures to MirroCraft and see if they have an old guy on staff who can identify it. Or, I'd probably justify it to myself as usual.

 

[lightflyer1]

I have a 1974 16' Mirrocraft Deep Fisherman F-3696 I think from the old brochure they sent me. From the specs listed that match mine is Center line length 16' Beam 63".
Hull thickness (Sides) .058 Bottom .064
Center line length 16' Beam 63"
Bow depth 30"
B.I.A. Motor size 35hp
B.I.A. capacity 1150
Approximate weight 242 lbs
These also match the plate in the boat for hp and capacity.
Four bench seats in it.

 

[airshot]

That 80" beam is the key ! Can't compare that to a 72" beam . Yours is a better built model, as a tiller the 55 might be a bit much, but with steering wheel you should be fine! I have a 16' Sylvan with a 78" beam and a side console, mine is rated for 80 hp...your 55 will work fine....run like a scared rabbit yes, but within safety regs....

 

[freeisforme]

This boat has only 3 bench seats with the middle seat being a pass through. The console sits on the right half of the middle seat, and the 6 gallon fuel tank sits behind the last bench. There is no battery, no electronics at all. The boat has no lights, no fish finder, yet. The ideal place for the battery would be inside the left halve of the middle seat but a size 24 battery doesn't quite fit. I may cut the top open and make it a hatch of sorts with a battery box secured to the bottom of the compartment. The battery weight would help balance out the boat a bit.
Another thought was to run a smaller, gel type battery, one to start the boat and one to run a fish finder and any lights I add.
The front storage area is large enough to hold an extra fuel tank, life vests, the anchor, ropes, etc.

It moves really well with just the 35hp, its more than fast enough for my use, but the 55hp is just sitting here and it would give me electric start.
One concern is that the 55hp will just burn more fuel, on top of adding more weight.
The current 35hp, which is a rope start only engine, weighs 111 pounds on the scale.
The 55 hp with no power tilt but electric start weighs 201 on the scale.
The boat will gain 90lbs exactly, plus the battery, (the one I have here, a group 24 deep cycle weighs 58 lbs.
I intend to upgrade the seat a bit, the folding plastic seat is just too flimsy for me, and I'll also add a proper passenger seat as well, likely up front. It'll also be getting a fish finder, chart plotter/gps, and a VHF radio.
The larger motor will require carrying more fuel as well, so a second 6 gallon tank is a must.
So the boat will gain about between 200 and 250 lbs before its set up for my use.

A few things came to mind as to swapping motors first is that if I add electric start to the 35hp, it really wouldn't need a full size battery, and a simple wheel chair size group U1 battery would likely be all I need to start the engine, so long as the motor remains easy to start and had some ability to charge the battery while underway. I'd add a second one just for the electronics. Another thought is that having the larger motor on there will make this boat less usable in smaller ponds, where gas motors are not allowed. I won't be able to just lift off the gas motor and hang a trolling motor instead. While the gas motor can remain on the boat legally, those ponds are shallow with lots of hangups, so losing the 200 lbs on the transom would be almost a necessity. In short, it would prevent this boat from every being used in smaller ponds, it would be a river and bay boat only.

That's not the end of the world, as I do still have my 15ft Starcraft, but that has a 35hp on the back too. That boat has a plate saying its good for 35hp, something I almost couldn't imagine though.
(Its also a step through mid bench style hull but tiller steer, no console). It absolutely flies with its 1978 35hp Johnson on it. Its what I was told was called the Alaskan hull. I'm not sure what's Alaskan about it but its got a long swept back bow shape and is super wide compared to other similar boats. The Starcraft is wide too but not as wide as this Mirrocraft. Its a short transom tiller steer model so I generally restrict it to calmer, fresh water. It has a 1054 lbs max cap. rating on the plate. Its motor is also manual start only, but the boat has a factory dual size 27 battery box in the port side rear corner and an area to secure a single 6 gallon fuel tank right in front of the motor. The fuel, battery, trolling motor, and my weight on the rear bench make that boat pretty heavy in the rear and I often carry two extra fuel tanks up front, if only for ballast weight.

 

[mirrocraft16]

This is the post that really got me to sign up here after a dozen or so years of reading.
These are by far some of my favorite aluminum boat hulls and by far the most trouble free over time.

I've got the more common 16ft version of your boat, mine measures 16ft and 2in long and 6ft wide on the button.
Mine has three bench seats and the same side console as yours. My plate says 50hp max 1,440 lbs max capacity.
I've seen a few like yours, but never figured out where they came from since they were never in the regular brochures, which seems to be a common thing with 70's Mirrocraft boats. I've seen variables in both length, beam, and transom width vs. the brochures. My guess was that they experimented a lot or made a ton of special order models back in those days. Rarely do you find any two that are identical in every way for some reason.
They did make a 17ft Sunsport in the 80's, I suspect your hull is an earlier rendition of what became the basis for the Sunsport model in the early to mid 80's. They were 16'-8" hulls with an 86" beam. Boats made after 1982 were built under the Northport name as well. It woudln't be much of a stretch to find that they built an open boat from what was normally a closed bow full interior model's hull either.

I run a 1985 30hp on mine, its got electric start and I carry a group 24 deep cycle battery that runs my fish finder and lights too.
I move my tank to in front of the rear seat when its just me. I had a 15hp on for a while, but got the 30hp when a neighbor decided to go four stroke on his boat. Its more than fast enough, but surprisingly not all that much faster than my old 15hp, which I kept just in case. It does burn more fuel, nearly double what the 15 used to burn, but it does stay on plane better with three guys in the boat. With two guys, there's not a ton of difference. I think alot of that has to do with the fact that both motors run at the same max RPM, so propped right, they both achieve the same speed, one just gets there a bit faster and has less trouble carrying additional weight. With the 30hp I don't have to worry about taking an extra tank of fuel because it won't prevent me from getting up on plane. The 30hp is faster though heading upstream, but only by a few minutes total over a 10 mile ride.
For my use, I really see no reason to go with a bigger motor, it would just mean more fuel. I use mine to fish, nothing more, and i don't get out nearly as much these days as I used to, so I'm quite happy with how it sits now. The only change I do plan to make is to ad some new rod holders all around the boat and some tie down straps for a cooler on the bow.

Of the two models in the brochures, looking from 1973 to 1986 or so, are the Lake Fisherman and Deep Fisherman, the Lake model is wider and longer, with lower gunwales, the Deep model is shorter by a couple inches and has roughly 8" deeper sides and a narrower beam width. From what I've gathered over the years they marketed the Deep model more in coastal areas and the Lake model in freshwater. However, I run mine in the back bays and even out in the ocean a bit a few times and its by far a better boat due to its wider beam width than having a narrower, but deeper hull. The Lake model draws less water overall and tends to stay on top of rough seas better if the occasion arises. both have about the same amount of total space inside since the Deep Fisherman model has not bow plate.

30 years ago, when I lived in PA, a local rental outfit on a nearby lake had a fleet of Mirrocraft boats they rented out.
They all had 1980 Evinrude 135hp V4 motors with tiller steer and manual only starting. When I saw that I had to try one, but soon realized that they were likely detuned severely, they were pretty fast but no where near as fast as one would have thought.
Maybe they were just worn out, but they were all late 70's model hulls with four bench seats, yellow in color as most were, and had 'Lake Fisherman 16' spelled out on each side. They were new enough to have decals not plastic Mirro Craft emblems, and they had brackets added that spanned from the motor to the rear seat bench, either to make tank removal impossible, or to reinforce the transom. I tried to buy one when they closed up in the late 90's but couldn't find out who owned the boats, then one day they all got hauled away. I've always hoped that one of them would turn up for sale sooner or later but so far, after 25 or so years I've not seen any of them.