Concerns About 4 Stroke Weight

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MrGiggles
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Concerns About 4 Stroke Weight

Post by MrGiggles »

I have been running a Suzuki DT75 on my 17' Tracker Deep V for a couple years now. It works okay, but I have been keeping an eye open and happened to see a 2010 Merc 4S 90hp pop up for pretty cheap that needs some work.

If it is fixable, I'd sure like to hang it on the back of my Tracker, but the weight concerns me. That Merc is a monster, based on the Verado block (same powerhead from 75-175hp), weighing in at 400lbs. The heaviest 2 stroke 90hp is closer to 300.

The boat is rated for 90hp, but that was long before 4 strokes were ever a thing. It is not very back heavy, just the battery and the gas tank, the battery could be moved under the drivers seat pretty easily, but the gas tank needs to stay. There is not much that I could do to move weight around.

Would anyone else be concerned with the weight? What about reinforcements on the transom?

Weldorthemagnificent
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Re: Concerns About 4 Stroke Weight

Post by Weldorthemagnificent »

90hp is 90hp as far as thrust is concerned for transom load. In the water the weight shouldn't make much difference as far as load and force. Towing would be were you see the difference. A transom saver would be good to have. As far as how the boat would sit in the water, you could add weight to it now to see how it acts.

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LDUBS
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Concerns About 4 Stroke Weight

Post by LDUBS »

Not sure what year your boat is. I'm thinking if your 17' Tracker is the same spec's as models over the past few years then it would kind of follow you should be OK with the four stroke 90. I guess my thinking is if the similar model is OK with a heavier four stroke why wouldn't yours be the same. Of course, I could be all wet (pun intended!). Maybe talk to Tracker for peace of mind.

I think WeldorTheMagnificent right about concern with trailering and trim.
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MrGiggles
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Concerns About 4 Stroke Weight

Post by MrGiggles »

LDUBS wrote: 25 Sep 2021, 20:22 Not sure what year your boat is. I'm thinking if your 17' Tracker is the same spec's as models over the past few years then it would kind of follow you should be OK with the four stroke 90. I guess my thinking is if the similar model is OK with a heavier four stroke why wouldn't yours be the same. Of course, I could be all wet (pun intended!). Maybe talk to Tracker for peace of mind.

I think WeldorTheMagnificent right about concern with trailering and trim.
It's an 84. Pretty similar to the V17 models all through the 90s, but the current 17' deep Vs are a lot more substantial than mine.

I replaced the transom wood last year, so it's as strong as it was when new.

It's got a transom saver that I plan to keep using.

turbotodd
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Concerns About 4 Stroke Weight

Post by turbotodd »

100 lbs is a big difference, depending on the hull

put 2 more batteries in the back of your current rig and see how it sits. If you can get used to it, go for the 90. Or look at a different brand 90hp that is lighter. I know the Merc 90 is cheap and they are cheap-for many reasons. When it comes to repairing them you'll quickly find out why I say that.

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DaleH
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Concerns About 4 Stroke Weight

Post by DaleH »

I don't see it worth the hassel ... and for what, maybe 5mph more? And who runs @ WOT all the time anyway?

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LDUBS
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Concerns About 4 Stroke Weight

Post by LDUBS »

DaleH makes a good point. I'm always concerned about adding weight to the boat. I'm going to bet your boat is pretty peppy with the current 2 stroke 75.

I've had my current boat since 2018. I'm going to say I have been at truly WOT for easily less than 30 minutes total. I can cruise along at 29 to 30 mph at less than WOT and feel like I'm moving pretty good. Of course those guys with big 100+ HP OB's pass me like I"m standing still. But I eventually get there and I bet I use a lot less gaso than they do. :D

I will add there is a whole list of pros & cons about two stroke vs four stroke. I don't want to open that debate, but you might want to consider that aspect too.
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MrGiggles
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Concerns About 4 Stroke Weight

Post by MrGiggles »

DaleH wrote: 30 Sep 2021, 09:21 I don't see it worth the hassel ... and for what, maybe 5mph more? And who runs @ WOT all the time anyway?
LDUBS wrote: 30 Sep 2021, 12:45 DaleH makes a good point. I'm always concerned about adding weight to the boat. I'm going to bet your boat is pretty peppy with the current 75.

I've had my current boat since 2018. I'm going to say I have been at truly WOT for easily less than 30 minutes total. I can cruise along at 29 to 30 mph at less than WOT and feel like I'm moving pretty good. Of course those guys with big 100+ HP OB's pass me like I"m standing still. But I eventually get there and I bet I use a lot less gaso than they do. :D
The Zuke runs okay but I have been having more and more issues with it, and it has an ever decreasing parts supply. The idle air passages in the carbs are screwed up and I have never gotten it to idle very well. A new set of carbs is pretty expensive.

It will do just over 30 as-is. The reservoirs here are long and spread out, 10+ mile runs to the honeyhole are not uncommon.

I'm not really doing it as much for the horsepower as I am the fuel savings and having a quieter, smoother, more modern outboard. Most are in love with their 4 stroke.

I have the Merc all torn apart and parts ordered, gaskets were the biggest expense. A fuel issue torched the #4 piston, but the bore is not hurt badly. All told I will have probably $1500 in it, including new controls.

Next time I take it out I'll try to find some sand bags or something to weigh down the rear and see how it sits.

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LDUBS
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Concerns About 4 Stroke Weight

Post by LDUBS »

I admit I like my four stroke. Mine is a 50 HP. Comes in at about 200#. I always thought my boat was a little stern down at rest. But up and running the power trim makes a huge difference. Fuel efficiency is pretty darn good. Less hassle. Clean. I read they are mechanically more complex, but that is beyond me.

Sounds like boat trim is going to be your primary concern.
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MrGiggles
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Concerns About 4 Stroke Weight

Post by MrGiggles »

LDUBS wrote: 30 Sep 2021, 13:20 I admit I like my four stroke. Mine is a 50 HP. Comes in at about 200#. I always thought my boat was a little stern down at rest. But up and running the power trim makes a huge difference. Fuel efficiency is pretty darn good. Less hassle. Clean. I read they are mechanically more complex, but that is beyond me.

Sounds like boat trim is going to be your primary concern.
More complex for sure. The guts of this Merc are taking up half of my shop. It is, in essence, a 1.7l DOHC car engine turned on end with a remote oil sump.

SteveBob
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Concerns About 4 Stroke Weight

Post by SteveBob »

I know that mine is smaller as it is a Suzuki 20hp but it is a 4 stroke. The differences could be (and probably are) extreme between smaller and larger outboards. But the 3 things I love about my 4 stroke is electronic fuel injection (no carbs to fiddle with and easy starts), it's much quieter, and no fuel premix. All 3 are a major plus to me. That and it is only a few pounds more than most similar size 2 strokes. Just my 2 cents worth on the subject.

turbotodd
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Concerns About 4 Stroke Weight

Post by turbotodd »

MrGiggles wrote: 06 Oct 2021, 13:20
LDUBS wrote: 30 Sep 2021, 13:20 I admit I like my four stroke. Mine is a 50 HP. Comes in at about 200#. I always thought my boat was a little stern down at rest. But up and running the power trim makes a huge difference. Fuel efficiency is pretty darn good. Less hassle. Clean. I read they are mechanically more complex, but that is beyond me.

Sounds like boat trim is going to be your primary concern.
More complex for sure. The guts of this Merc are taking up half of my shop. It is, in essence, a 1.7l DOHC car engine turned on end with a remote oil sump.
More complex is subjective. Some of the two stroke engines are less complex--but the key word here is the engine. Remember there is more to an outboard than the engine. On some of the ETEC's (and others) they have high pressure direct injection; basically a crude version of what modern cars use. So then you have a very complex fuel system that feeds the engine which is controlled by electronics that were designed and programmed by people. In this case that's where the 4 stroke is much more reliable in the long term. The technology of a 4 stroke DOHC engine has been around for about 100 years and has been proven. Yes there are more parts. That doesn't mean they're less reliable because they have more parts. It just means they have more parts inside the engine. Big deal. A 32 valve V8 automotive engine will have 32 valves, 64 springs, 64 keepers, 4 cams, 2 or 4 chains (or sometimes a belt), 8 pistons/rods/pins, 16 clips (sometimes), bearings, oil pump, gaskets, etc. By going off of the numbers of parts inside, OMG they have to be unreliable because there's more ways for them to go wrong. But in reality, they run for hundreds of thousands of miles (tens of thousands of hours) when properly maintained. Most of the time any damage to them is operator or owner incurred.

Similarly, most of the time a 2 stroke engine damage is operator or owner incurred. In other words, forgot to put oil in the fuel, let the gas/oil mix sit for years and foul jets, run lean, destroy cylinders, or sometimes let them sit and they get dirt dobber nests under the cowling (no air filter), fire the engine up and take off...eats dirt...self destructs. Or in the case of high pressure direct injected engines such as etec and some yamaha 2 stroke, they're real sensitive to fuel and real sensitive to poppet valves & thermostats. FICHT is similar, IMO FICHT is garbage but that opinion is based on working on FICHT jet ski's. Again, sensitive--or more sensitive than a comparable horsepower 4 stroke.

Downside to 4 stroke of larger HP is because of more parts, IF something goes wrong, it costs a little more to repair. Thus, take care of your stuff.

The weight difference between 2 and 4 stroke is getting narrower as time goes on.

20 years ago a 4 stroke outboard was rare. Today around here it's about all you see. It's not because they're forced upon us, I mean new cars with better emissions are 'forced" on us yet a lot of us still drive old stuff, it's because they really are better in a lot of ways; one of which is a far superior idle quality and secondly they typically use about half as much fuel as a comparable 2 stroke.

Far as hour use, I'm sitting here looking at an F300 on a Sea Hunt 26, that has 4385 hours on it. If the average speed of a car were 45 mph, that would equate to just shy of 200,000 miles, just to give you an idea. I can't say I remember a 2 stroke with that many hours but most of the old 2 strokes didn't have hourmeters either.

MrGiggles
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Concerns About 4 Stroke Weight

Post by MrGiggles »

turbotodd wrote: 07 Oct 2021, 22:35
MrGiggles wrote: 06 Oct 2021, 13:20
LDUBS wrote: 30 Sep 2021, 13:20 I admit I like my four stroke. Mine is a 50 HP. Comes in at about 200#. I always thought my boat was a little stern down at rest. But up and running the power trim makes a huge difference. Fuel efficiency is pretty darn good. Less hassle. Clean. I read they are mechanically more complex, but that is beyond me.

Sounds like boat trim is going to be your primary concern.
More complex for sure. The guts of this Merc are taking up half of my shop. It is, in essence, a 1.7l DOHC car engine turned on end with a remote oil sump.
More complex is subjective. Some of the two stroke engines are less complex--but the key word here is the engine. Remember there is more to an outboard than the engine. On some of the ETEC's (and others) they have high pressure direct injection; basically a crude version of what modern cars use. So then you have a very complex fuel system that feeds the engine which is controlled by electronics that were designed and programmed by people. In this case that's where the 4 stroke is much more reliable in the long term. The technology of a 4 stroke DOHC engine has been around for about 100 years and has been proven. Yes there are more parts. That doesn't mean they're less reliable because they have more parts. It just means they have more parts inside the engine. Big deal. A 32 valve V8 automotive engine will have 32 valves, 64 springs, 64 keepers, 4 cams, 2 or 4 chains (or sometimes a belt), 8 pistons/rods/pins, 16 clips (sometimes), bearings, oil pump, gaskets, etc. By going off of the numbers of parts inside, OMG they have to be unreliable because there's more ways for them to go wrong. But in reality, they run for hundreds of thousands of miles (tens of thousands of hours) when properly maintained. Most of the time any damage to them is operator or owner incurred.

Similarly, most of the time a 2 stroke engine damage is operator or owner incurred. In other words, forgot to put oil in the fuel, let the gas/oil mix sit for years and foul jets, run lean, destroy cylinders, or sometimes let them sit and they get dirt dobber nests under the cowling (no air filter), fire the engine up and take off...eats dirt...self destructs. Or in the case of high pressure direct injected engines such as etec and some yamaha 2 stroke, they're real sensitive to fuel and real sensitive to poppet valves & thermostats. FICHT is similar, IMO FICHT is garbage but that opinion is based on working on FICHT jet ski's. Again, sensitive--or more sensitive than a comparable horsepower 4 stroke.

Downside to 4 stroke of larger HP is because of more parts, IF something goes wrong, it costs a little more to repair. Thus, take care of your stuff.

The weight difference between 2 and 4 stroke is getting narrower as time goes on.

20 years ago a 4 stroke outboard was rare. Today around here it's about all you see. It's not because they're forced upon us, I mean new cars with better emissions are 'forced" on us yet a lot of us still drive old stuff, it's because they really are better in a lot of ways; one of which is a far superior idle quality and secondly they typically use about half as much fuel as a comparable 2 stroke.

Far as hour use, I'm sitting here looking at an F300 on a Sea Hunt 26, that has 4385 hours on it. If the average speed of a car were 45 mph, that would equate to just shy of 200,000 miles, just to give you an idea. I can't say I remember a 2 stroke with that many hours but most of the old 2 strokes didn't have hourmeters either.
Let me pick your brain a little then.

I did a compression test on this Merc. 175. 175, 175, 80 in the bottom cylinder. Stuck a borescope in #4, confirmed mild scoring and the piston didn't look too healthy.

Got it up on the stand and torn apart. #4 piston has bad detonation damage on the intake side. Intake valves were also very tight clearance wise, like zero. Bore damage was very minimal, very light hone took care of it. A new piston and rings will fix it up, but I'm not really sure what caused it, or how to prevent it from happening again.

Brought the injectors to a speed shop and had them cleaned and flow tested. A-ok, #4 was not plugged or dirty.

The rail is fed from the bottom, and there is a check valve right under #4. The only theory I have is that a little bit of water or ethanol settled in the rail and caused it, or the injector plugged temporarily and eventually passed it. Both are a bit of a stretch IMO.

It's only got 330 hours and lived on a pontoon.

There is no scoring on the sides of the piston, or discoloration that would indicate it overheated.
PXL_20210925_220456659.jpg
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turbotodd
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Concerns About 4 Stroke Weight

Post by turbotodd »

Pontoons. Yes.

They are the hardest on outboards.

You need data. What's the maximum RPM with a normal load? It needs to be close to maximum recommended by the manufacturer. Most builders will prop them such that, if say the max is specified at 5000-6000, they'll prop them so that they run 5000 and call it good. On a 4 stroke, you want it as high as possible, even a hundred or so over is ok if the load is light. Then on a Pontoon, if it was propped to run 5900 with a normal load, and the whole family shows up with all their gear for a weekend, now they're lugging the motor, maybe 4500 wide open? That will hurt an engine.

Detonation--I don't really see evidence of it in the picture? Plug burned off? Ring land broken? Burnt piston? That pist5 minutes later it was purring. No, seriously, purring. That's what they sound like at 700 rpm. Called him up, said come on down and check it out, shows up 45 min later and is astonished. He had spent almost $1400 in trying the other guys, they couldn't get it but they also didn't have the same tool I did (which some idiot eventually broke and mercury went everywhere).

on looks more like it's corroded than anything but I'm not there to inspect it. Perhaps it had some water ingestion at some point? Had it seen salt?

Thermostat stuck open? Opening too soon or too late? Poppet valve?

Also overfilling the crankcase can lead to it-and with the amount of black on the piston crown, that wouldn't surprise me.

Tight valves are a usually a maintenance issue and possibly a defect and/or foreign debris (dirt dobber ingestion?). Tight valves won't generally cause preignition or detonation, that is normally either a lean mixture issue or a spark advance issue. Or both. Most valves have a coating on them, and when the coating wears off, the face gets damaged and wears off quickly. Then the intake valves suck up into the head and clearance goes away, then it loses compression. I'm working on one now that's done that. 19 Wolverine X2 850.

So to compare, a 2 stroke. I've done quite a few of them. Seen PLENTY of holed pistons, burned pistons, stuck rings, unexplained seizures....specifically, carb motors and HPDI's. On small carb motors, they'll premix the things at 25:1 or 50:1 in some cases when they're supposed to be 100:1 on the sub 40hp. Dump a bunch of oil into some gas and call it good. Then the ring lands get carbon'd up, they stick, the engine cannot dissipate the heat from the piston to the cylinder and into the cooling water, and it holes a piston. Seemingly, unexplained...until you check the fuel. Also with fuel, vented fuel tank, mixed fuel, it sits and the gasoline evaporates and leaves a lot of junk behind. I tested this in a mason jar on a hot day in the shade. 40% of the fuel I poured into the jar evaporated in 8 hours' time. And, when gasoline evaporates, it gets cold (evaporative cooling), and then condenses moisture out of the air and now you have water in the fuel for "no reason". 2 stroke owners are notorious for being old school (and I respect that, by the way), with vented metal fuel tanks. Today's fuel ain't like yesteryear's fuel and a non-vented new-style fuel tank is almost a necessity. Seen plenty come through with burnt powerheads, owner forgot to put oil in the gasoline.

poorthang
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Concerns About 4 Stroke Weight

Post by poorthang »

open that image in a new tab, then enlarge it. you see the results of detonation/lugging at the 6-8 oclock position. it broke away the top ring land and damaged the ring. my guess, based on one picture, would be too much load or over propped, as mr turbo stated. that kept the piston rocking until the land was damaged, then the oil comsumption and burning on the piston top occured. BLACK DEATH it is called. if i am right, replace the rod and related pin and bearing. and, remember, all the little specs of piston, and crystalised burned oil went directly into a running engine.

while it is apart, i would tear the crank out and inspect it, and then the oil pump. if an aluminum bodied geroter oil pump, i would replace that too.