Inboard motors & lower units = problems????

muskie hunter

Petty Officer 2nd Class
Joined
Jul 29, 2007
Messages
158
I been reading here quite a bit. I keep hearing the same things " my motor blew up" or " my lower unit went out" Alot of the stories are from people with newer boats. The mercruiser 5.7 is basically a chevy 350. This has been a great durable motor for chevrolet. I dont know much about the lower units but it would seem to me that not much should go wrong with them. Are boats that much harder on engines? Why so much problems w/ these things? I have heard of sucking plastic bags in and cutting off the waterflow to the motor, but man dont people watch the temp gauge.
I am scared to deth to buy an inboard because of all the bad publicity. Am I missing something? Can someone explain the problems?

Thanks Steve
 

ParallaxBill

Petty Officer 1st Class
Joined
Aug 27, 2006
Messages
341
Re: Inboard motors & lower units = problems????

You are only really hearing the bad news here. Most of us never have problems with our I/O rigs. Nothing bad happens so we don't talk about it as much.

Mine is 35 years old entirely original with probably thousands of hours on it from area lakes to the Atlantic ocean. Doesn't sound like any reliability problems with mine. I'm sure that the majority will do as well if maintained properly and routinely.

I'd also like to hear the entire truthful stories from those that claim their boats just "blew up". Everything that fails fails for a reason. :)
 

scoutabout

Lieutenant Commander
Joined
Oct 14, 2006
Messages
1,568
Re: Inboard motors & lower units = problems????

Yeah -- interesting skew as bill says. Most people don't come on and post about how wonderful their boat is running. Just like the 5.7 litre, the little 3.0 litre inline four Mercruiser I had in my 1996 SeaRay is a bulletproof engine that Mercury has used for decades. I certainly didn't have a moment's trouble in ten years of active use beyond a cracked coil insulator. My stepfather has an early seventies Starcraft with the same motor that is still running quite strong.

That being said, marine use is far harder on an engine owing to the higher loads and almost WOT many of them run at day in and out. I believe though that valve train and other components are strengthened for marine use in motors that were originally automotive-based.

Now outdrives are a little different. You'll find your fans and detractors for all models but basically they should all give you years and years of hassle-free use AS LONG AS THEY ARE SERVICED AND MAINTAINED PROPERLY. Check and replace exhaust and driveshaft bellows as needed; ensure no water is entering the gear casing; check alignment as required; keep gimbal bearings properly torqued; ensure everything that needs lubricating get that all-important shot of marine grade grease as needed. I've probably missed a few items but a good service manual will cover all the bases. Manuals are good to have even if you never lift a wrench. At least you will have a level of familiarity with your rig that allows you to talk intelligently with the people that are (or are pretending) to service your boat. Oh, yeah, and try not to run it into anything if you can.

You already mentioned keeping an eye on your gauges which tells me you're not the turn the key and forget it kind of boater. Combine that with operating the thing sensibly within its performance limits and you will be set.

So...come on in...the water's fine!
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: Inboard motors & lower units = problems????

i hear all the time my boat won't start. etc. i ask when was the last maintainance. never is usually the answer. i have a '99 5.7 with Vovlo SX drive. so far bullet proof, with regular maintainance.
 

Wotam

Petty Officer 2nd Class
Joined
Jul 22, 2007
Messages
108
Re: Inboard motors & lower units = problems????

Off the top of my head, here are the typical I/O trouble posts:

1) Cracked Block
Failure to winterize (drain the block so it doesn't freeze).

2) Water in boat/driveline damage
Failure to inspect/change/maintain outdrive 'bellows'.

3) Carb Problems
Failure to maintain fuel or fuel system. (Gas stabilizer, keep the tank FULL in storage)

4) Cracked/Warped Heads
Overheating - failure to change water pump impeller.

5) Outdrive failure
Failure to inspect/maintain gear lube & seals.

6) Electrical problems.


Of the above failures, outboards are usually immune from #1, and #2... which does take a fair chunk of problems out of the picture.
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Inboard motors & lower units = problems????

i hear all the time my boat won't start. etc. i ask when was the last maintainance. never is usually the answer. i have a '99 5.7 with Vovlo SX drive. so far bullet proof, with regular maintainance.

I remember back when you had that Merc you were changing manifolds on , that you would NEVER have another IO, only outboards from then on................ :p;)
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: Inboard motors & lower units = problems????

i'm part owner, and don't do the maintainance. i only work on OBs.
 

05GlastronSX

Chief Petty Officer
Joined
May 29, 2005
Messages
437
Re: Inboard motors & lower units = problems????

There are too many possible points of failure for me in an I/O. I enjoy being in them and dont have anything against them...i just would never buy one. Outboards only for me. The ease of maintenance when compared to an i/o is incredible and not to mention, outboards are meant for use in water whereas an i/o is just a marinized 4-stroke car engine that would much rather want to idle all day rather than run at high rpms like 2 stroke outboards. Too much maintenance for me in i/o's.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: Inboard motors & lower units = problems????

I prefer outboards. I play with older ones and can snatch one off the transom and replace with another in about an hour--and these are mid range 90-150 hp. They are easier to work on and generally just as long lived as inboards. My buddy takes his I/O to the marina and spends 300 to have it winterized. Then he is at their mercy as to when he can pick it up. I just tilt my engine vertical to let water run out. True, both have good and bad points: outboard uses more fuel and is noisier.

As for marine use: the Chevy 350 in a car does about 1500 rpm at about 50 mph and is probably producing 20-50 hp to keep the car going. On the water, the same engine rarely is run at less than 3500 rpm and produces 100-200 hp to keep the boat going. The more horsepower produced, generally the shorter the service life of the engine. Extreme example: the 350 in a dragster produces 5-8,000 hp. Its expected service life is 5-8 seconds and about 800 revolutions. ( this is the total number of revolutions the engine actually turns from burn-out to finish line.)
 

scoutabout

Lieutenant Commander
Joined
Oct 14, 2006
Messages
1,568
Re: Inboard motors & lower units = problems????

I do have to admit that, after a decade of I/O life, I'm really enjoying my first four stroke outboard. Everything neatly contained in one package that would be easily transerred to another hull (or removed and housed in the garage for extended maintenance without filling the rest of garage and driveway with boat). My initial post was just to assure our friend that I/Os are certainly not the neverending horror show he was thinking they might be.

As for noise - it's different - at least in the power ranges I've experienced. With the SeaRay I/O there was noticeable outdrive and exhaust noise while the engine itself was pretty quiet. With the Yammy 90 outboard the engine noise is more pronounced while there's not much exhaust noise (and of course, zero outdrive noise).

Fuel consumption I haven't quite nailed down. Off the cuff guess would be the 90 Yamaha on an 1,800 lb boat is burning about as much as the 135 Mercruiser on a 2500 lb boat. Top speed on both is about the same at 40 mph.
 

lmannyr

Master Chief Petty Officer
Joined
Jul 5, 2007
Messages
815
Re: Inboard motors & lower units = problems????

I'm all about inboards. They are made with parts (about 80%) used in gm cars on the road. The parts are much cheaper because of the great number of parts available for these engines. As long as you know the differences in the parts of the two (I/O and Outboard), it's just like working on a good ol' chevy.

But anyways, opinions are like ( use your word of choice here ), everyone has one.
 

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: Inboard motors & lower units = problems????

If cost was not a factor, id guess i outboard would be the way to go. However a 200+ outbaord alone is 15000 and up which preclude's this old boy from one. With that said, i have learned to do quite a bit of work myself on the I/O, check the lube on lower leg before going out, checking to make sure the oil is up before going out and a full tank of gas. Now once a year i have to take 45 min to a hour and drain the block and shoot a little oil in the carb, if i didnt have to bend over to open those drain ****'s and changing that oil. it might take 15 mins....;)

Every three year's change the impeller, im really likin this Volvo setup take's about 30-45 min's,with efi there's no carb's to mess with, the electronic igniton is trouble free and well the plug's yep that's a 1/2 hour every 3 yrs a real pain Ya know what i mean....:D

:eek: Uhhh then's there's damm wax job's......but that's another story...;)
 

salty87

Commander
Joined
Aug 12, 2003
Messages
2,327
Re: Inboard motors & lower units = problems????

inboards for me too and none of that outdrive stuff, thx

outdrives just seem too complicated. different lubes and gear oils to use, bellows to replace, tilt issues. i do like that they are often chevy v8's but the outdrive is a complicated mass of machinery that's dangling in the not so friendly water with some rubber keeping the water out.

straight inboard, little different from the first oldsmobile i drove. maintenance is very simple.

granted there are performance issues with all 3 choices but that's not the focus of this discussion.
 
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