Repower Considerations - Added HP vs Added Weight

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RedHatRedNeck

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Location
Centerview, Missouri
Current Rig - 2004 1860 SC Triton with a 2002 Mercury 40 EFI Big Foot 4S

A repower may be in the plans for some future mods I want to do and looking into people's experiences. Weight to go from 40 to 60 hp is only about 10-20lbs additional weight. A 75 or 90 is over 100lbs.

Aside from adding more weight, the main drawback I'm considering with the repower idea is just how little fuel this motor guzzles while at cruising speeds. I can normally run 4+ hours at half to 2/3 throttle and maybe burn 4 gallons if I punch it up a bit.

Has anyone repowered an 1860 from 40 to 60, 75, or 90 hp? What were the increases in top speed, performances, and how much fuel economy did you lose?

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On my 16 foot StarCraft V-hull tin boat I went from a 40 to a 60 and never looked back. One day I had a little over 1 gallon in one of the tanks and ran at cruise for a good 8 miles before she ran out of gas, that’s pretty good! And the power was there when you really wanted it or when carrying more people.m

I had the prop pitched for a standard load of 3 to 5 people in it and if alone I’ll be right at the rev limiter, but I don’t cruise at WOT anyway. But will run there for at least 15-minutes every trip on the way back in, just help clean out the carbon.

Bob Stearns, a noted marine author, once rigged and tested the SAME boat with a 75, 90 and then a 115hp outboard motor; each pitched properly and set up for best performance for motor mounting height. The 90 was the best overall choice, only 1 MPH slower at cruising speed (than the 115) but much improved efficiency in MPG. At WOT, it was 3-4 MPH slower, but like I said ... who runs there? The 90 was more efficient than the 75, which while not lugging, was ‘struggling’, so one had to run it st higher RPMs.

I think I’d get the 60 myself ...
 
My buddy's dad has a welded 1860 with a 60hp 4stroke Merc Bigfoot. I don't have an idea what its efficiency is but it ran well with 3 of us in it plus gear on the river....fast enough that WOT was beating us up, so we backed off and cruised comfortably at probably low 30's.
 
I know you are looking for a 60 HP, but thought I would share this in case it helps. I have a 50 HP four stroke on my 18' windshield boat (dry weight, no motor, is 750#). I can cruise along close to 30 MPH at a little over 3/4 throttle (power trim is a wonderful thing). I usually run a short distance and then troll for hours. I haven't accurately measured gaso consumption but typically get two top-offs out of my 5 gallon can. My boat is rated for up to a 60 HP. The original package included a 40, which I felt was kind of low for the boat. I opted to spend the extra $$ for an upgrade to the 50 HP. I'm pretty happy with the performance but wouldn't have walked away from a 60 HP, for sure. Anyway, I agree with the previous posts recommending going with the 60.
 
If the boat is rated for 90hp max, run a 90. The manufacturer gave it a rating for a reason. Weight? 100lbs on the back of an 1860 is peanuts. It'll take it just fine. Some 90's are heavier than others, so shop around. A 40 on that hull must be an absolute slug, I'm assuming that's why the consideration of repowering? A lugged 40hp will use close to the same amount of fuel as a properly set up 90 at cruise RPM because the load is completely different.

Don't like 90? Look at the Yamaha F70. It is an awesome motor, BUT, you'll have to change controls, cables, and some of the wiring. One of many things that the F70 has going for it is that it was originally thought of as a pontoon motor, using a slightly different gearcase ratio than most others in the same class, which helps get the engine RPM up a little when coming out of the hole. They perform BETTER than a comparable 70hp 2 stroke-and this is from personal experience since I just repowered a Tracker 1754, from a Yamaha 70 2 stroke to a F70 4 stroke. I have personal experience with that boat; have fished out of it a few times on the river, and it always performed well. After the repower-and yes there was a slight increase in weight-it's faster, uses a boat load less fuel, MUCH quieter (it's quieter at full throttle than the 2 stroke was at idle), and picked up about 4 mph (from 32 to close to 37). At idle speed the only thing audible is the pee water hitting the lake. Pull the cowling and you hear the injectors "ticking" at idle. Highly impressed with it! And....it's not all that much heavier than your current 40hp (maybe 30 lbs?)
 
Main thought is concerning the weight overall. Does the 1400# max rating of persons motor and gear count the hull weight too? The main mod I want to do is to.the cockpit to where it's 2 up front 3 in back seating. Right now if there's 3 people in the boat it's not the greatest seating arrangements to be able to see the way I would like. I'd be getting new steering cables anyway as I'd be moving the helm forward.

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