4 stroke motors

[Huskie]

How long have the 4 strokes been out? Were there many problems with the early models before they became very reliable? I'm looking at a few rigs that have early 2000 yamaha's any experience with them, 100-150 horse, thanks.

[SandBayFishCamp]

4 stokes have been out for many years. Yamaha first released thier 4 stroke 150hp in 2004. I own the unit and have been very happy with it. However, you need to invest in an external 90/gph fuel filter (about $100) because the unit has fuel injector screens that can clog easily. This problem isn't unique to yami's but some would argue they are more prone to the problem.

All said, I have a 18' aluminum boat with a 150 w/19" prop. Does 50mph with 2 people, half tank of gas and both live wells full. Great hole shot. Quiet, even at WOT.

[mamohr686]

I would stay away from any early 4-stroke with carbs. They can be finicky if out of tune. Fuel injected models are much more reliable and very trouble free.

[solbes]

I wouldn't necessarily steer you away from carb'd 4 strokes. They have been out for many years. I think they are still very reliable and with proper fuel care can last MANY years without problems.

Here's something I dug up on the internet of Yamaha 4 stroke introductions (please note, it's only as correct as the guy who originally posted it. Also I cutoff everything less than 50 hp):

1999: 50, 80, 100

2000: 50, 80, 100

2001: 50, 80, 100

2002: 50, 60, 80, 100, 115, 200, 225

2003: 50, 60, 75, 90, 115, 200, 225

2004: 50, 60, 75, 90, 115, 150, 200, 225

2005: 50, 60, 75, 90, 115, 150, 200, 225, 250

2006: 50, 60, 75, 90, 115, 150, 200, 225, 250

2007: 50, 60, 75, 90, 115, 150, 200, 225, 250

2008: 50, 60, 75, 90, 115, 150, 200, 225, 250, 350

In 2003 the F100 and F80 became F90 and F75 respectively to more accurately describe their horsepower. They are the same engine, so an older F100 would really be an F90. Also the F90 and F75 went EFI in 2005 (carbs before). I believe the F150 came out of the gate as EFI, but someone should verify this.

[SandBayFishCamp]

Yes, my 04 F150 is EFI

[Ufatz]

Just for historical perspective, I had a 5-horse four stroke Honda

OB on a shore boat in AK in the early 70's. But we often had stuff way before any of the lower 48 folks even knew about them.

I mean, we were using satellites when there were only a FEW of them up there!! Ha!!

[solbes]

If you are looking at F100's and F150's I would steer towards the F150. It's EFI and actually puts out more than the 150 it claims (closer to 160). It's a very well respected engine and kind of the bread and butter Yamaha.

The F100 will be carb'd and puts out 90 or less horsepower. Still a good option if it's on a smaller or much cheaper rig. What boats are these mounted to that you are considering? Cost difference?

[Huskie]

The Yammie 100 is on a 1750 Alumacraft, both 2000 models, just concerned if it was an early model before thay had the bugs ironed out so to speak. I don't like motor problems, have had too many in the past. Carbs in that one, what is the concern about being careful with the fuel that one reply commented on? I've never owned a 4 stroke before and this rig is in my price range, wish I could afford the newer injected models though. The 150 is on a bigger boat, just outside of what I want to spend.

[solbes]

A F100 should move that Alumacraft pretty good, 39-42 mph would be my guess unless they were narrower back then. With carbs you want to make sure your fuel does not varnish and cause clogs. Typically this means adding some type of fuel stabilizer into all gas you use. Also using Yamaha Ring Free (or seafoam) on a semi regular basis is good practice. Nothing difficult, just add's a tad to cost of ownership.

You would will like the fuel efficiency of an F100 if you are accustomed to 2 strokes in the past.

[SandBayFishCamp]

Not sure if carb based motors are subject to the same problem as EFI ones. However, I have had two Yamaha mechanics tell me (after I had clogged injectors) that an external fuel filter is necessary because of the trash that is in fuel today, even ethanol free fuel.

Solbes comment on ring-free is also something that was recommended by the mechanics to run on a constant basis.

I had my injectors clog up twice in my first 15 hours of owning the boat before the external fuel filter. I have since put on 130 hours...no problems.

Fuel efficiency is also improved with 4 stroke EFI. I can get about 7 mpg at cruising (at 3000 rpm, 27 mph) and about 3.5 mpg at WOT (at 5300 rpm, 50 mph).

[Hookmaster]

I have a 1999 F100. One fuel pump started leaking after a few years and both were replaced due to some issues with that batch (irregularities in mating surface so gasket would leak). I've had the carbs cleaned once with a resynch and the carbs resynched once without cleaning. It has been a very good motor for me but wished I had the fuel injected F115.

[marine_man]

The biggest thing with all carb'd four strokes is to keep good or stabilized gas in the carbs when it sits without use. The emission regulations are tight enough that the carbs are jetted pretty small, and it doesn't take much to plug them.

marine_man