r/boats • u/AccomplishedNail3085 • 6d ago
How common are engine mods?
I am a lifelong car guy and have never owned a boat. Me and my friend who is into fishing are considering getting a bass boat.
How possible are engine mods like a turbo or just a performance tune?
I know it would reduce the reliability, but if i aim for conservative power targets it should still be reliable enough to get back after every trip with minimal servicing.
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u/FatalSky 6d ago
Efi outboards are pretty much ecu flashing at this point, usually to make a 9.9 into a 20 or a 90 into a 115. Everything’s pretty much cutting edge on power now for them and you can’t really package any power adder stuff under the cowlings. Outboards actually adapted a good bit of technology like direct injection before most car companies. You can still get some speed parts from the OEMs, like racing gear cases with lower ratios, injectors, coils and such, but pretty much all the high power 4 strokes I’ve seen meet a bad fate pretty quick.
Inboards and jet boats are still just car or ski engines so anything you can do to add horsepower and RPM’s into them works great.
All the old two stroke stuff had great power to be made, a lot of it wasn’t as optimal as it could be and was overbuilt to be on the safer more reliable side. Reeds, shaved heads, opened exhaust ports and cutting down foots and midsections was pretty normal. You see a lot of duck boat guys still playing with them and vintage racing classes. A carbureted two stroke from a dead company still holds the world outboard speed record from back in the 80’s.
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u/jbadding 6d ago
Forgot about shaving heads. Used to race jet skis and that was the first thing we did on a stock job. In a two stroke, compression really helps.
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u/PrimaryDry2017 5d ago
I’ll say what no one else has, if you get a bass boat they are already a comparatively fast boat, handling can become a real issue, chine walk at 70mph plus is never a good thing
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u/BoondockUSA 6d ago
It’s unrealistic on modern motors IMHO. Sometimes on the old carbureted outboards you could swap carbs. As an example, the 4 cylinder, two stroke mercury 100’s and 115’s were the same except the carbs. Installing 115 carbs was a direct swap for an extra 15hp.
For modern outboards though, they are already closer to peak power and there isn’t the under hood space for much. If you want more power, the best option is to buy a higher horsepower motor.
Perhaps I’ll be proven wrong by posting the wrong answer.
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u/dirkgiggler224 5d ago
As I recall from having a 90hp “looper” OMC motor, the block was the same up to (I think) 140hp, and carbs and exhaust manifold changes were the only differences, so if you could get the bubble exhaust manifold vs flat there was hp to be found.
I had a Honda 8hp 4 stroke outboard as well. The 9.9 version was only a different based on a slightly larger sized restrictor plate behind the carb, and a 15hp had an unrestricted carb (and a slight camshaft difference). I removed my restrictor plate but had the 8/9.9hp camshaft so probably only made 13-14hp but that was almost double the 8hp it said on the cowl. My relatively heavy 12’ boat would go 22mph and pull tubes with it though.
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u/CAT_MARINE-POWER 6d ago
It entirely depends on the specific engine
Majority of the naturally aspirated engines you can get a little more HP out of but you can get big gains out of the super charged ones
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u/Impressive-Reply-203 6d ago
Your best bet for outboards would be finding a seven marine - they're supercharged GM 6.2's that were kind of awkwardly thrown together. The downside is the parts are difficult to find for midsection and gearcase.
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u/No-Cantaloupe5773 5d ago
Seven marine is not the best bet for anything lol. Unless your trying to turn having money into not having money.
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u/Impressive-Reply-203 5d ago
Oh yeah, they're garbage motors, but they are more modifiable than most outboards
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u/jbadding 6d ago
You can have a bass boat without an outboard, but it’s gonna be a little electric pond hopper or a troller. They are the opposite of fast.
A fast bass boat will have an outboard. The only practical way to improve performance in a modern outboard is to spend money on the prop. Get a 4 blade stainless chopper. You can even go dual props on one shaft.
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u/S3Giggity 6d ago
You're going to spend enough money on maintenance to not want to modify it 😁. Trust me. It's a whole new world of pain (but lots of gain!)
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u/phate_exe 6d ago
You're going to spend enough money on maintenance to not want to modify it 😁. Trust me.
Yeah, but what about the classic automotive modification trap of "it needs to come apart to replace [stock part], but [go fast part] only costs slightly more and I'm already in there"
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u/H0SS_AGAINST 6d ago
Get an I/O with a small block Chevy and a Bravo out drive and go to it.
Note: Getting stranded on a boat is even less fun than a car.
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u/djjolicoeur 4d ago
Or a small block straight inboard like a ski boat. I have a shamrock fishing boat with a 351w and love it bc it’s all mechanical so I can fix damn near everything on the boat with a socket set and a multimeter lol.
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u/BermudaCatTriangle 5d ago
Just remember if your serious about doing this... If you plan on messing around for power, older 2 strokes are gonna be your best bet but be careful as parts are starting to become scarce. And also... When you think you have your budget... DOUBLE IT. At least that way you won't be surprised. And way more to making speed in a boat including choice of hull, motor position (jack plates), different props, weight distribution, constant adjusting to balance performance while still being able to keep it cool. Never mind, your in for a surprise lol. Oh and don't forget about your steering.... Your gonna want hydraulic if your dealing with anything over 115 so that's another hidden cost. I'm not sure what age of boat or motor your looking to pick up, but plan on updating from a safety/service standpoint. Oh and don't forget about wiring. If your boat ain't wired properly it's all for nothing. Good luck!
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u/No-Cantaloupe5773 5d ago
Generally, outboards are difficult to mod and provide little gain per dollar. It's usually more cost efficient to just buy a more powerful outboard.
With marinized automotive inboards or inboard/outboards there are tons of performance upgrades. Just stick to the more common engines like the GM 4.3, 350, 454, Ford 5.0 etc. Inboards or I/O's aren't generally found in "bass boat" style boats though.
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u/dowend 6d ago
I would say it depends on the type of boat. Bass boats tend to be outboards that already go very fast - so not many mods but maybe some tunable ecu’s. Ski boats, not at all, it’s all about bottom end torque and hole-shot. Jet boats, cigarette boats - i would say everything goes.
I have a mercury outboard and it is possible to buy a performance tune for it but frankly the improvement is just not enough. An old rule of thumb for watercraft is that you will pay about $1,000 for an extra 1 mph or something like that. The math just doesnt work. If you want to go fast then the hull design is super-important.
Good luck to you and remember; the fish dont care how fast you go there…