15hp Johnno tell tale

[BaitThrower]

Hi all, Just got a 1986 15HP johhno off another forum member here in good nick (thanks Wayne). Just a question about the flow of water from the telltale though. On my 5HP suzi, it flows a consistent amount, no matter what revs (or at elast at idle it still pumps out heaps). On the johnno however, it will be at a real slow flow at idle (almost so you can see individual drips instead of a stream) and only forms a stream when you rev it a little, the stream appearing to flow in linear amount against the engione throttle, i.e. the more throttle, the more flow. This sounds like it might be fine or normal?? but I just wanted to check this was normal for these motors. I havent been able to get the 15hp in the water yet, only in a flush bucket so I havent tried it at full throttle yet to see if it really starts pumping it hard then. ('d have water everywhere! I don't want to take her out if there should be more water flow than this and risk breakfdown or engine damage :)

Any confirmation or otherwise appreciated.

Dean

[FNQCairns]

I dunno now which has which or when each individual brand/model/hp changed/didn't change etc but there are two differing types of water pump on outboards also there are shades of grey as well.

1. type is the pressure pump it will have more vanes and they are are fairly short.

2. is the volume type pump which usually has longer vanes and less of.

Of coarse I am not talking lots of pressure but with these types the tell tail can be reactive with throtltle, more so than the higher volume designs which seem to keep a more constant stream at low rpms.

Not saying this is the reason on your individual engine just something to consider, pretty much if it doesn't get hot to the touch it simply is not overheating, it's worth doing this easy test when on the water straight after doing some different speeds.

cheers fnq

[wayneoro]

hi mate put it in water mate then u can tell what u described could be normal with ears on . try putting your hands over the muffs put pressure on them use a big bin full water cheers mate

[BaitThrower]

Cheers guys. I was testing in a bin full of water. No muffs. I reckon it is ok coz doesnt seem to be any blockage and it starts pumping well with a bit of throttle. Cant really do muffs coz I store boat in the carport and would have water going everywhere :)

She doesnt seem to overheat but I havent really checked this. I was able to touch the flywheel (I think thats what its called) and no burn, but the motor had been sitting for 10 mins after shutdown when I did that. I'll retest again in a couple days.

Got RMDL license class on Saturday!

[tunaticer]

I would trace back the telltale hose inside the motor cowling to where it goes into the powerhead. Take the hose off the hose tail then unscrew the hosetail. Quite often there can be a marginal blockage with something like a fish scale or something and give erratic results. My personal experience is usually a small piece of shellgrit or more recently a spiderweb. Aparently a spider had built its web in somewhere in the water pickup (probably behind the grille) anmd when i started the motor it got pumped through the motor and partially blocked the hosetail as a stingy ball of webs.
Removed the obstruction and no more problems.

Jack.

[SunnyCoastMark]

Hey Dean,
Even at idle - you should have more than a steady drip coming out of the telltale. As others have said - check for blockages and kinks. Mud potter wasps are notorious for making nests in telltales. Use a piece of fencing wire or sturdy coathanger wire. If that doesn't help you may have to drop the leg and check the impeller.

Mark

[steve99]

Hi Bait thrower,

I had a 25hp Yamaha a few years ago,and the telltale water was always constant regardless of engine revs.

If yours only dripples (like an old man ) the impeller is cactus. Check telltale water temp after its been idling for a few minutes. It should only be luke warm - any hotter, and you need a new impeller - $150 should cover it.

It only takes about 5 second of running without water through muffs to destroy the impeller, or when they wear out with age, they usually do so on a linear scale, thats why they need more revs to operate effectively

Rather than run the risk of damaging the engine, I'd get it looked at before it becomes terminal.

Cheers Steve99

[wayneoro]

mate there are heaps wasps in my garage and the motor had not being started for 3 mths

[BaitThrower]

ok well ill check the hose to the telltale from the block and see if i can clear it (seems tricky to get off, not much access for fingers!)

Then if that is clear, I might attempt to take the leg off and check the impeller, and hopefully dont break anything :)

Dean

[BaitThrower]

Good news. Last night i stuck some trimmer line up the telltale hole and hose to the block to see if it would clear anything. Then today tried again. Seem a little better. Then I got the compressor out and blew some compressed air up the telltale. This went right through the cooling system and exhausted out the water intakes down below. After doing this, the telltale is now pumping full charge with a good strong stream. Far better than the drips it was producing previously. So there was something blocking the system somewhere along the line.

Just glad I checked this before taking her out ont he water. Could have ended up with a very hot engine! :(

[SunnyCoastMark]

Good news Dean!

Make sure you keep an eye on her though. I would pobably repeat the process after she has been for a good run - just to make sure.

Happy boating;D

Regards,
Mark

[BaitThrower]

Yep, I think I'll make it part of my regular maintenance and running cycle from now on :)