70 hp cutting out problem

[SwordsBeginner]

Hi all, I have a 2 stroke Evinrude 70 HP engine, which came with a boat I purchased. The engine is circa year 2000.

The boat/engine was lying up for a while before I purchased it, but the engine started fine. I had a marine mechanic look at it before I went on the water. He cleaned carbs etc. and said engine was in great condition.

This engine ran/idled fine with muffs on.

However on the water, I have been out five times now. everytime I have a problem with the engine dying on me on increasing revs (slowly *).

After the second trip I went back to the marine mechanic to ask about this and he increase the idle speed. But this has not solved the problem.

* If engine running at idle in water and I increase throttle slowly the engine will die, however if I put the throttle down quickly and get the engine to a high roar the engine will not die and the boat takes off (quickly). I can decrease throttle then to a reasonable rev.

I have changed fuel tank, hose and this made no improvement.



PS I did notice today that the throttle cable flexes/moves when throttling.

Any ideas?

 

[Daviet]

Re: 70 hp cutting out problem

Could you post your model number so we know what engine we are talking about?

 

[SwordsBeginner]

Re: 70 hp cutting out problem

E70pleea

 

[SwordsBeginner]

Re: 70 hp cutting out problem

Out again today, same thing. Engine starts ok, idles, When I apply throttle slowly it cuts out. But when I start by pushing the throttle to full power the engine does not cut out and the boat flies off.
Anyone?

 

[Brokeback Johnson]

Re: 70 hp cutting out problem

Sounds like fuel delivery problems.... most likely the carbs are not truly clean.

 

[SwordsBeginner]

Re: 70 hp cutting out problem

I took Carbs off to have a look (ie. to chech the mechanic had cleaned them ). They are spotless inside, in fact the wjole engine is well maintained as its an ex_RNLI Coastguard engine.

The engine has three carbs connectected by a bar, and on the middle carb I noticed the butterfly valve ? inside had a tendancy to stick when opened sometimes, depending on the force I used to flick it open.

The top and bottom carb butterfly valves did not stick.

A tiny loosening adjustment of the nut and clamp that hold the bar seemed to free it. Like it was over tightened.

Might this be the cause of my problem?
When the three carb butterly valves are linked up.


I have not refitted carbs yet.


Sorry for bad technicial descriptions.

http://s694.photobucket.com/albums/vv308/Whitehall_Bohs/carbs/

 

[jtexas]

Re: 70 hp cutting out problem

1999 model.
Your throttle valves must be closed at idle, parallel throughout their range of motion, and perfectly horizontal (not beyond) at WOT. Any other result causes unpredictable performance.

Your description says you loosened a nut, did you mean the "screw" holding the throttle shaft clip in place?

Anyway don't leave it loose. You should be able to position the clip such that the throttle shaft won't bind after you tighten it down. If you have to, take the boat out & run the motor with the airbox cover off, so you can observe the throttles while your symptoms are happening.

One other thing to check: make sure the timer base is moving smoothly without sticking when you advance the throttle. (see pic)

 

[Ironsides]

gone...

 

[SwordsBeginner]

Re: 70 hp cutting out problem

thanks jtexas,

The screw I loosened (ever so slightly) is on the opposite side of the carb than your picture.

The bar that the butterfly valve sits on is held into the carb (on the opposite side) by a clip which is screwed in.

The middle carbs butterfly valve was catching on opening. Loosening that screw (less than a quarter turn) stopped this catching.


My problem was the engine was idlling ok but cutting out on gradual increased revs. But the engine did not cut out on sudden increased revs (ie if I slammed the throttle down).

I'm thinking now this valve was sticking and flooding the engine (petrol smell at times when cutting out). However on hard throttle it was ok presumably because the bigger vibrations shook the valve and released it from its stuck position.?

Does this sound plausible? Would a stuck valve cause a cut out?

 

[Home Cookin']

Re: 70 hp cutting out problem

try squeezing your ball as you accelerate to see if that cures it. If so, it's fuel pump, bad lines, etc.

 

[Home Cookin']

Re: 70 hp cutting out problem

One other thing: I had something similar with a 1972 Merc 200 (20hp). It would die on acceleration; my mechanic and I knew it had to be fuel related. Turns out, when the parts up under the flywheel (stator, etc.?) advanced from idle settings to run settings--the parts physically moved--a wire with bad insulation arced against the block.
Outboards are famous for one problem mimicing another.

 

[jtexas]

Re: 70 hp cutting out problem

If it sticks closed, the motor will idle normally, but it would be unable to accelerate, just as you say, unless you forced it open with the sudden movement. This scenario wouldn't flood the motor though, and it doesn't usually die when one cylinder drops out; it would just bog down and run about half to 2/3 normal speed.

If a throttle valve sticks open, I'm pretty sure that cylinder wouldn't fire at low RPMs, but that motor will idle surprisingly well on 2 cylinders. I suspect you are correct that idling with the throttle open on #2 would flood that cylinder. It would also be reluctant to accelerate until the throttle control reaches a certain point, where the spark is advanced and it's getting enough air to bring #2 on line, then it would take off. This is more or less a theory.

I saw your picture of the screw...unless it's tight you risk having it vibrate out, but obviously the sticking valve is unacceptable. So if you can, get it tight without sticking, otherwise, maybe put some loctite on the threads.

Do check the movement of the timer base, also the wiring in that area as homecookin suggests, little things like that are what causes unusual symptoms like you described. Like if one the plastic fittings holding the linkages together breaks and falls out. That sort of thing.

 

[landyman]

Re: 70 hp cutting out problem

if its an ex rlni engine ring bill higham marine in the uk. i had exactly the same problem with mine. the carb settings are way different to what the standard engines use to counter all the mods that the rnli do to make them run upside down and submerged. they will be able to give you base settings that will get you going that you can then fine tune to get it running perfect.
(swords and bohs?? i'm guessing your a dub then!!)

or if you can wait till friday evenin i'll check my settings for you

 

[jtexas]

Re: 70 hp cutting out problem

if its an ex rlni engine ring bill higham marine in the uk. i had exactly the same problem with mine. the carb settings are way different to what the standard engines use to counter all the mods that the rnli do to make them run upside down and submerged. they will be able to give you base settings that will get you going that you can then fine tune to get it running perfect.

now I see, there's two military version 70-horse motors, a 1994 model 70RNLIA and a 1996 model 70RNLIB.

hmmm......do those carbs have a part number on 'em?

 

[landyman]

Re: 70 hp cutting out problem

mines actually a 2004 model!! it drove me nuts with the bogging and stalling i then spent an hour and a half on the phone to bill higham himself and he talked me thru all the mods that the RNLI do (Royal National Lifeboat Assoc) basicaly the engines have to run upside down for 15secs and submerged for 15 secs so they have all sorts of sealed airboxes/fuel delivery systems. these are then removed when the RNLI release the engines for re-sale. mine came with 134 warranted hours on it.

 

[SwordsBeginner]

Re: 70 hp cutting out problem

now I see, there's two military version 70-horse motors, a 1994 model 70RNLIA and a 1996 model 70RNLIB.

hmmm......do those carbs have a part number on 'em?

carb main part 339172
carb bottom 330503
carb butterfly valve 341200

 

[SwordsBeginner]

Re: 70 hp cutting out problem

If a throttle valve sticks open, I'm pretty sure that cylinder wouldn't fire at low RPMs, but that motor will idle surprisingly well on 2 cylinders. .

All three valves are connected by a bar, so if one sticks would it hold the other two open with it.

The screw I slightly opened is still tight, just not over tightened

 

[SwordsBeginner]

Re: 70 hp cutting out problem

thanks Landyman, I'm defo a Dub

I might give Billy Bingham a shout if I don'nt get sorted.
The engine had no Evinrude id plates, just RNLI id stickers on it, so it was difficult to even know the year.
RNLI thought it was 2003 from their own numbers.
It's imacculate and runs well and strong apart from this problem, which I fvell is something small, but as was said small problems trick other problems

Thanks again everyone

 

[landyman]

Re: 70 hp cutting out problem

its to do with the idle screw settings being out slightly. its idling a little lean so when it comes off the idle circuit and on to the slow speed jets it cuts out. thats a common enough problem on them. did you try choking the engine when you give it throttle?

(galwegian meself)

 

[SwordsBeginner]

Re: 70 hp cutting out problem

Thanks Landyman, what is slightly worrying is that the marine mechanic I used said he'd adjust the idle by moving a screw/screws on the bar that connects the three carbs.

jtexas' picture (and my suspicions) point to the idle setting screw being not near the carbs