jackplate

[dhughes49]

I test drove a 2002 kenner today with a mercury 200efi with a jackplate . I noticed that when the owner raised the motor the tell-tale stream would stop streaming. It appeared that the water intake was still underwater. I have never had a boat with a jack plate but it seemed wrong to me . can someone with jackplate knowledge explain this to me

 

[crabby captain john]

Re: jackplate

If the motor is running and intakes are in the water it should Pee. Other than raising the intake above the waterline the jackplate will not effect the stream. If still in the water there is a problem with the impellor/pump.

 

[UncleWillie]

Re: Jack Plate

Re: Jack Plate

...I noticed that when the owner raised the motor the tell-tale stream would stop streaming....it seemed wrong to me...

You are correct ! It is Wrong!
The Tell-Tale is there for a purpose. No Tell-Tale, No water flow, No cooling!

Most tell tales are taped into the water flow at the exhaust manifold just before it dumps down the drive leg.
The tell-tale water is about as hot as it gets. Being almost too hot to touch is normal.
It may get your attention but is should not scald you! If it does something is wrong.

 

[jcfitzgerald]

Re: jackplate

No telltale after raising=insufficient or no cooling water. It would be a red flag to me to run from that possible purchase.

 

[littlerayray]

Re: jackplate

since it isnt your boat and you are thinking of purchasing it i would avoid it like the plague

 

[spoilsofwar]

Re: jackplate

Could be an air leak in the water intake upstream of the impeller? When the motor is fully down, the spot is underwater and so water pressure is retained. When the motor is raised, the spot is above water level and the impeller is sucking air. Just a guess.

 

[crabby captain john]

Re: jackplate

I would wonder how much use the motor had with the jack up and no cooling going on. My mechanic would need to look at it and I'd still be leery about paying more than the value of the boat and trailer.

 

[Bob_VT]

Re: jackplate

Forget the tell tale............ install a water pressure gauge. When running at high speed or any speed you want to be able to look forward and not keep turning around.

BAD sign if water flow stops!

 

[gm280]

Re: jackplate

Forget the tell tale............ install a water pressure gauge. When running at high speed or any speed you want to be able to look forward and not keep turning around.

BAD sign if water flow stops!

I understand what you are talking about, but a water pressure gauge isn't a cure all. It just shows pressure and not flow. There could easily be a stopped up water flow and the pressure gauge would show pressure with zero flow... A Tale Tell stream is still the absolute best indication things are working properly... Water pressure gauges are like volt gauges, that being they both show partial capabilities but not water or current flow... Flow gauges (Tale Tell stream) and current meters show usage... JMHO though!

 

[metriccrescentwrench]

Re: jackplate

It just shows pressure and not flow. There could easily be a stopped up water flow and the pressure gauge would show pressure with zero flow...

That's incorrect, in fact a lot of the time a pressure gauge is just T'd in with the tell-tale so they're looking at the same thing. There's a tap in the water jacket where the tell-tale comes from, and usually an orifice to restrict flow out the tell-tale, so that in fact the tell-tale is actually just an indication of how much pressure is inside the water jacket. Spend some time looking at the water flow diagram from an engine service manual and you'll understand.

 

[UncleWillie]

Re: jackplate

Flow, Pressure, It all depends on where the blockage is.

The tell tale is just before the manifold dumps down the drive leg.
There were a dozen easier/more restricted spots to get a blockage other than in the last two inches.
As the flow goes up, the pressure goes down.

The gauge you want is an engine TEMPERATURE gauge!
That is all that really matters!

 

[NYBo]

Re: jackplate

The gauge you want is an engine TEMPERATURE gauge!
That is all that really matters!

Not really. If the sender isn't immersed in water it will give a false, usually very low, reading. So the ticket would be both a temperature and a pressure gauge to be really sure of what's going on.

 

[Frank Acampora]

Re: jackplate

It IS possible to have enough water to keep the engine from overheating and not activate the alarm--yes, all Mercury engines have an overheat alarm--yet still not have enough pressure to have water flowing out the pisser. Additionally, since it is an EFI engine I would bet strongly that the computer would either shut it down in the event of an overheat--or at least go into limp-in mode.

However, I would be extremely cautious about buying this engine. It very well may have been abused. AT THE LEAST, I would want a compression test on all cylinders to be certain that they were not scored due to overheating burning off the oil film from cylinder walls.