No thrust in forward !?!

[HalcyonS]

Its July - sunny sailing , except that I had an overheating event, a water pump episode, a distributor episode, a new battery. So today, I'm taking a friend out for the first sail in over a month… yu'd think I deserved a break. But no. Engine started right up, running like a top, dropped mooring lines, threw it into gear - nothing. Nothing. No thrust.

Sailed for a while. started engine, put it in fwd - thrust! Tried again later - nothing. Back on moorings, I ran the engine. I checked shifting from cockpit and from engine compartment. There is the usual detent 'click'. It seems to seat into position. But no thrust. There seems to be thrust in reverse.

An interesting thing happened the other day, while testing engine on moorings - I rev it up and down in neutral - fine. Rev it up slowly in reverse, from 900 to 1400 was fine, then the engine races by itself up to about 2500. Repeated this a couple of times to make sure I wasn't imagining it. I thought about that for a while and decided it was cavitation. was it?

The boat has sat for a couple of months may and june. I hauled in December and everything looked fine prop-wise.

I'd be grateful for any advice.
thx
Simon

Apart from the possibility that my prop dropped off,

[Sony2000]

Check that your drive shaft is still well attached to the transmission.

[tenders]

Everything in your description COULD be tied to barnacles on the prop. Is it clean? They can grow fast in the summer.

[HalcyonS]

side issue

Barnacles are unlikely I think, I hauled December and had none - maybe its LA harbor water is toxic to them or are they cold water critters? - I see mussels, small sponges, etc on the bottom of my dinghy but not barnacles. No weird vibrations like a blade fell off.

I have a big old 3 blade prop and am used to seeing the turbulence over the stern when motoring. That is not happening, though it *seems* to be driving in reverse, judging by turbulence again. As I said, I'm on a mooring so I usually run the engine load test in reverse. Yesterday's test - after running in neutral and reverse, I ran it in forward. In a light breeze, it wouldn't even make the mooring lines to the buoy go slack, ie no thrust at all!

I don't seem to have any of the usual problems, like being stuck in gear, etc. More like no drive to prop shaft, or no prop, though there does appear to be thrust in reverse, so I'm thinking transmission.

Is there a transmission adjustment faq? I am not clear on the way it functions, though I know reverse and fwd are entirely different processes. I can confirm that it is not the cockpit control linkage. Same at engine. And anyway, the builder of my boat did everything top class, its a 3/8" rod linkage, no cable there !


If anyone could suggest a diagnostic procedure, I'm all ears.
I didn't think to check the prop shaft, this would clinch it. Next visit.
Step 1 would be check for drive at the prop shaft I suppose
Step 2 look at/for the prop
but inside the transmission is a black box to me.

thx
S

[Carl-T705]

Step 1 and 2 should produce the answer you're searching,

[roadnsky]

Here is the Reversing Gear adjustment procedure.
Do you have the MMI Manual?

[HalcyonS]

Jerry thanks, very useful
No (shamefaced) I do not have the MMI 'bible'. I'll put it on my birthday list.
S

[HalcyonS]

transmission adjustment, helpful video

http://www.youtube.com/watch?v=Y6SJ15NPh0A

camera work is a bit shakey, but if a picture is worth a thousand words, a video is worth a thousand pictures

[sastanley]

Halcyon...you need to put the engine in gear and see if the shaft is spinning.

The 'racing' in reverse may be because reverse is really a brake band that shifts the sun & planetary gearset around to make it spin the other direction. It is quite common (unless you have a stiff shifting cable) and necessary to hold the shift lever while in reverse to keep enough tension on the brake band to facilitate reverse.

edit - I will also comment that when my prop is dirty I don't get the "propwash' out the back like I am used to either, the engine is really lethargic. mussels may have decided to take up residence on the prop.

[gmilburn]

Not to hijack this thread, but do most A4 owners start their engine in gear? My A4 starts so easily, whether it is in gear or not, but was wondering if I'm naive about damaging something, particularly after reading this thread! Do most start in gear or neutral?
Gary

[romantic comedy]

I dont start in gear. It is more strain on the starter and engine.

[roadnsky]

Do most start in gear or neutral?

Gary-
Start in Neutral.

...I will also comment that when my prop is dirty I don't get the "propwash' out the back like I am used to either, the engine is really lethargic. mussels may have decided to take up residence on the prop.

Halcyon-
Shawn makes a very good point.
Can you go over the side for a quick peek at the prop and shaft?

[JOHN COOKSON]

I didn't see this in the thread. Maybe I missed it.
When there is this sort of problem disconnect the linkage and shift by hand. The problem may be in the shift linkage not the tranny.

TRUE GRIT

[HalcyonS]

Egg on face dept

Jerry and Shawn -

> Can you go over the side for a quick peek at the prop and shaft?

ahem. Prop looked like a football. (he ducks as rotten tomatoes fly). All clean now.

Odd because I hauled 6 months ago, and the hull stayed clean. Do you guys paint antifouling on your props? I haven't, I thought I picked up word that it was a bad idea (I use Petit Trinidad)

[tenders]

I've tried to paint my prop. The action of the water on the spinning prop quickly wears most of the paint off, and barnacles regrow there. Some paint stays around, near the hub, and does fend off some growth but not in areas that matter much for prop efficiency.

I've also used some kind of expensive clear Interlux spray - same result.

Desitin, ie diaper rash cream, was once rumored to work on props - it wears off immediately and does absolutely nothing.

Tom at Indigo has recommended not zincing the prop and letting some electrical potential ward off the growth, with the cost of gradually dezincifying the bronze in the prop and the risk of eventual prop failure - seems like the medicine there is worse than the disease.

There just isn't an effective substitute for mechanical scraping.

Would there be a way of copper plating a prop? If aesthetics were not an issue I wonder if that could be done cost-effectively every few years.