Pino wrote: Hi deafwish,
thanks for replying. I will check the impeller and t-stat housing on blockage first. If i cant find anything i will check the manifolds and risers. When i bolt off the risers the water canals are visible?
Im new to this inboard thing so forgive me if i ask the obvious. There is another thing: the temp. gauge needle stays at 160 degrees when i turn the power off. Is this normal or should the needle drop to zero? Maybe its a possebility its faulty.
I dont think im cavitating because there is no pitting on prop surface if thats possible on a SS prop. There is no unusual sound to be heard. How can i determine if there is any cavitation going on?
What do you mean exactly with cilinder settings on current tach? Is it possible to use any kind of tach or is it matched to the engine?
I guess prop hub slippage is a very bad (expensive) thing and not easy to check?
Again forgive me if i ask some stupid questions because inboards are new to me and english is not my native language.
He may have put old manifolds back on a new engine. You can tell if the manifolds are passing enough water through them by feeling them with your had during or just after running engine. You should be able to put your hand on the top of the manifold and keep it there even at cruising power (it will feel "hot", but not hot enough to make you pull your hand back). This is true even with a bad thermostat...because regardless of thremostat open or closed, all of the water pumped in goes out through the manifolds. However, if the manifolds are blocked (rusty inside), then your engine will not get enough water to cool properly.
You can check the manifolds by removing the upper half (the elbow), but you must drain the water out first, otherwise the water will spill down into your exhaust valves. There is a drain at the bottom of the manifold for this purpose (and for winterizing)
Gage reads 160 when off: No this does not sound normal, so you may have a bad gauge.
Bad thermostat? Thermostats often last 5 years or more, but they do go bad, and they don't cost much, so at least add one to your spare parts.
Propeller: Your 43mph at 5200rpm sounds like not enough pitch on the propeller. 20 pitch sounds about right, but maybe that prop is not the same as it is marked. It may have been "re-pitched" by a propeller service. See if you can find a prop shop to look at it, or see if you can borrow a prop from a fellow cobra owner or prop shop to see how it does with another prop.
Prop Slippage? If you are accelerating quickly without the engine revving abnormally, then you don't have prop slippage. (prop slippage can sound like a car with a bad clutch). If it does slip, then it needs to be be re-hubbed which costs about $50-60 at a prop shop.
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