Yanmar1gm10 gearbox

A

alapicz

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Hi
I have some trouble with my gearbox(or engine).On neutral gear my engine can easily reach max rpm but on forward Gear thinks change.On my last trip engine could not reach even a half rpm ,on revers gear I think rpm are much better. Just today I went to the boat and I have check air and diesel filters all fine, I let my engine work on forward gear for 10 min and when I touch gear box it was hot rather then warm.I have check gear box oil and it's over limit but I'm don't think that can cause the problems.i don't have any vibration from propeller except when I switching from forward to reverse but it shaking just for few seconds.any idea what can be the problem?
 
Overpropped?
My 1GM10 powered boat is slightly overpropped and I quite like that. If I need to stop fast I can with a burst of reverse. It will still hit hull speed going forwards though it won't hit max revs. The only downside is that it doesn't do "slow". Even tickover revs will get me up to 2 knots which is a bit too much in a tight marina.
 
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When was the last time the oil was changed? Every 100 hrs is good.it should not be black or dirty. If you overfill this will cause problems. I guess its a small GB so it will get hot. Is your hull and prop clean?
 
hull and prop was clean and antifoul this year(in april) i don't know when oil was change,when i touch it today it was not sticky,regards overprop i had not any problems in the past except once 2 years ago when i was approaching France and rpm drop to max 1200 but next morning everything return to normal
 
my engine refused to rev properly when the hull was fouled. It just wouldn't reach full revs a month after a scrub. Came out for a scrub and it's great again. This year fouling has been the worst i've ever known. the symptoms are exactly the same as overpropping, i didn't get any black smoke but the engine just couldn't turn any faster flat out. if this is a new problem, maybe that's what's happening.
 
Hm last time I have tested my problems tight to pontoon in marina so boat was not moving but I still couldn't reach my max rpm, will scrub be still to considerate in this case?
 
Tied to the pontoon, is the worst case, it provides the maximum loading on the prop and engine, this a "bollard pull" test, were the advance coefficient is zero.

It's equivalent to having the hull so badly fouled that the prop won't move the boat at all!

Or looking at it another way, tied to a pontoon, there is very little water flow over the hull, so the condition of the hull makes no difference.

So I'm not surprised you can't get full revs when moored to a pontoon.

You need a clean hull and prop to know if fouling is the cause of the high gear box temperature.
 
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