Any Engine Doctors out there?

M

Memphis_Chung

Well-Known Member
Joined
11 May 2003
Messages
136
Location
Southampton
Visit site
Hi All,

So, the boat is back in the water and the weather this morning looked good for a quick motor up the harbour. Switched the donk on (it is a Volvo Penta 2002 18hp) with great excitement and anticipation. This is what happened:

1. throttled forward in neutral - fine
2. throttled back - fine
3. throttled forward in gear - fine
4. throttled back in gear - revs dropped to 500 and would not go any higher regardless of throttle. This was followed by the exhaust spewing out black smoke and a sludge of unburnt diesel.
5. Throttled forward - fine
6. Throttled back - same problem

The only way I could get reverse to rev normally was to throttle forward and then stick it in reverse without pausing at neutral.

The only other thing I noticed was that the engine was idling slightly fast from time to time (1200 instead of 850 ish).

I couldnt see anything wrong with the throttle cable/linkeages but then again, I am no expert.

Any ideas????

Thanks,

Tom
 
Don't know the set-up at all, but if there is a reverse idler cog in the gearbox, it sounds as though it's bush or shaft has seized. Which could be expensive if it turns in the casing.

If it works like a normal gearbox, that is.
 
I have pretty much ruled out jamming as the prop turns fine and the engine revs normally when I put the boat directly in reverse from forward (without stopping at neutral). I hope it is not the gear box!
 
I'm not familiar with the Kiwi feathering prop but, as this is the only thing you have touched, I wonder if the blades don't take up the proper angle when you engage reverse and are sticking in the fore-and-aft position, thereby offering maximum resistance to being turned by the engine. This makes the engine work hard and push out black smoke.

You say you have greased it but did you use the correct grade of grease? Apologies if this is insulting your intelligence, but I have no way of knowing how experienced you are with servicing this propeller.

It's just a thought; no doubt about to be shot down in flames. /forums/images/graemlins/cool.gif

[Ach! Beaten to it by Earlybird, who always catches the worm!]
 
[ QUOTE ]
I'm not familiar with the Kiwi feathering prop but, as this is the only thing you have touched, I wonder if the blades don't take up the proper angle when you engage reverse and are sticking in the fore-and-aft position, thereby offering maximum resistance to being turned by the engine. This makes the engine work hard and push out black smoke.



[/ QUOTE ]

This is just what I would have said. The black smoke is unburnt diesel because the amount of diesel going into the engine is determined by the speed control lever whilst the air is determined by the engine speed. So if something is stopping the shaft from rotating frrely, the engine gets too much diesel for the air and it emits black smoke.

So the real question is what is stopping the engine from rotating in reverse gear. Likelty candidate is the one bit you've touched - the prop. Failing that, maybe sopmething round the prop.

The issue about going from forward to reverse quickly is easy to understand. If the engine is turning over a bit faster than idle speed it has more torque to overcome the resistance of whatever is slowing the rotation down. Bit like attacking a steep hill in your car when you've already got the revs up as opposed to attacking it from idle.
 
I have just had another thought. If the prop is not going into the correct position in reverse, wouldnt it have problems shifting into the forward postion on the few occasions that reverse has worked?
 
I'd be tempted to give it a bit more time, some thing has seized and may once the oil works it's self around be ok, if its the gear change linkages then try lubricating where it goes through the case !

cheers
Mick
 
It’s the Kiwi prop.

The blades are not completing their roller guided and spring resisted turn to the proper reverse position, thus giving you a massive reverse pitch.

Talk to Alan at Vecta Marine 01672 564456.

I fitted one last spring (Sadler 34 & VP 2003) and a couple of weeks later removed a 2 blade Kiwi.

Some 5 weeks later (mid May) re installed a factory rebuilt 3 blade Kiwi and while its good when its working it seems to have spent too much time not working properly.

I developed exactly the same problem as you about 3 months after re fitting it (fully greased with the correct grease). I have lived with it knowing its limitations since late August and will sort it when I get the boat out in spring for a wash down and touch up of the antifoul. (You can at any time re create the problem exactly by going through the reverse manoeuvre while tied up on the mooring, where you will note the substantial increase in side wash.)

We Sail mostly without engine and one other point I noticed when this started to happen is that it doesn’t feather very easily (shaft still running when in neutral) and it needs a hand full of the shaft to stop it, once stopped the blades seem to feather and its ok till the next time the engine is turned on and off.

The Kiwi has a peculiar reverse action where the blades are turned back on themselves by rotating against a roller when in reverse so as they are reversing in a semi forward position and not as you would expect just flipping over. I am sure Alan will explain it much better than I can. He is a good chap, very knowledgeable, helpful and honest.

That said when its working its excellent less drag than my previous 2 blade fixed prop but especially for a crash stop… smartly into reverse and a fist full of throttle.

Best of luck………. Peter
 
You must log in or register to reply here.

Other threads that may be of interest

B
Fly by wire remote issue
Replies
14
Views
389
Mr Googler
Mr Googler

Share this page

Top