Starting 4 stroke outboards

[jeremyshaw]

I have a Yamaha F15 Four Stroke, which is a great engine, but hard to start. Nothing wrong with the engine - it is just that it takes a lot of muscle. My wife can't start it and many a bloke has retired hurt.

I believe this is a general problem with 4 strokes, so I have been looking at an electric conversion or switching to a new motor with electric start.

Yamaha have now relaunched the F15 (and an F20 at the same weight which sounds good) and say:

"Getting these outboards started is made easier with a light-load manual starter that features a short-throw starter rope with a comfortable contoured handle. This system works with an auto-decompression device to make manual starts easy."

Does anyone have experience of this engine or similar engines (I think the Merc is a badged Yam) with auto-decompression, or can offer advice on whether this would be likely to make the 4 stroke as easy to start as a 2 stroke?

Thanks
Jeremy Shaw

 

[fluffc]

It's odd that you're having problems starting a 4-stroke outboard - they are not as hard as two-stroke.

Beware that the starting pull technique is different for a two stroke to a four stroke outboard.

For a 2-stroke, a short sharp pull is required.

For a 4-stroke, a long consistent pull is required. This doesn't have to be as fast as you would start a 2-stroke, but it is important that the full length of the starting cord is used.

 

[Lakesailor]

Mechanics really. There's only half as many firing strokes, (as long as you're comparing like with like - ie, twin cylinders) and I think it's right to say that compression is lower on a 2 stroke at cranking revs than on a 4 stroke. So less effort required.
As fluffc says, a long steady pull seems to work best. I have a Yamaha 4hp 4 stroke (single cylinder) and that's how I get my best results. 2 or 3 pulls should do it.
But if you find SWMBO can't manage it, I would think you're right to look for an easier solution. There's nothing worse than the nigglng concern that you can't get the motor going when you need it.

 

[Kawasaki]

As fluffc and Lake person have said.
There is a different technique needed.
Do the usual, choke setting, throttle setting etc etc.
Pull the starter cable out gently to its full extent, just slowly then thet it return.
Then pull from the "Home" position with a steady but firm momentum to the extension of the "pull" or till Your arm has run out of movement.
It aint the snatchy movement that is associated with the 2 stroke Brigade.
Hard to describe in print differently!

 

[oldharry]

[ QUOTE ]

It aint the snatchy movement that is associated with the 2 stroke Brigade.
Hard to describe in print differently!

[/ QUOTE ]

OR: a 2 stroke has to be spun as fast as the starter mechanism will allow to give it the best chance of starting. A 4 stroke doesnt need this speed, but needs more time being rotated steadily to ensure it fires.

With either engine a good one will fire almost instantly as it goes through the firing point anyway. (But try telling that to a Seagull owner! /forums/images/graemlins/smile.gif) I have had both types which just started with little more than tweaking the pull cord through the compression stroke. Also lots of others that needed time.....

 

[Lakesailor]

That's it.
A 2 stroke has to get it's charge and exhuast done in one cycle so as well as using the bottom of the piston moving downwards to push the charge into the cylinder they use "valve" overlap to use the scavenging effect of the exhaust gases leaving to help pull the charge into the cylinder. At low revs (ie cranking speeds) the charge may just rush out of the exhuast port and the compression may effectively be low. That's why a fast cranking speed is needed and why 2 strokes turn easily.
4 strokes fill the chamber on one stroke, compress it on the next, then the power stroke and then the exhuast stroke. On low power engines there is very little, if any, valve overlap, so speed is not an issue, but a full charge is drawn in and not lost before compression, so cranking compression is higher. Making it a harder job to pull over by hand. Your cranking does need to go right through a cycle, hence the need for a long pull.

 

[andy_wilson]

4 strokes

Never easy to start (IMHO) compared with a 2 stroke.

Anyway, the correct technique it to set the fuel supply, throttle, choke etc. ready for starting.

Extend the starter cord feeling for the height of compression and stop just before this point is reached.

Retract the starter cord and pull it as long and hard as you can, that way you guarantee as many compression strokes per pull as is possible.

 

[jeremyshaw]

Thanks for the advice everyone. I agree about the long pull needed for the 4 stroke. I've had this engine for 4 years (mostly liveaboard) so got to know it pretty well. As I said it starts just fine, the issue is it takes a lot of muscle because of the compression. Two cylinders, too, which must make it that much more difficult.

Four strokes are still uncommon in the Caribbean but the few yachts I know with one of this size agree they are hard (or I should say physically demanding) to start, and have bought electric starts or converted. Autodecompression sounds like a good improvement, but I'l have to do some more research to see if I can get a sense of the difference.