Yamaha 4 strk 9.9 cooling prob?

[Inselaffe]

Good morning all!

I went for my first sail here in Lisbon yesterday - luverly!

But I have a strange problem with the outboard:

At the end of last year, when Malagueta was still at home in Brightlingsea, the telll tale cooling water would not be there when I started the engine. I would have to suck on the tell tale outlet pipe to help it through, then it was fine, the water coming out was not too hot. If I stopped the engine though, when I restarted I would have to do the same again.

When she was out of the water & arrived on the trailer down here in Lisboa it was clear that the inlet water grills on the leg were all fouled up, and when I took them off there were mussels growing inside.

So I cleaned it all up (and even bought new plastic grills as one was cracked). I then ran the engine with a hose pipe & those 'earphone' thingies when she was still on the trailer for well over half an hour and the motor ran perfectly with very cool tell-tale water.

Great. Then she was craned into the water, motor started first time & I took her about 2 miles up the river under motor to her berth in Lisbon. Again no problems tell-tale water very cool.

Then yesterday It was time for the first sail. Started motor with first pull & didn't touch throttle, left it running on tick-over & got on with getting her ready to go. After about five or ten minutes all ready & gave motor a rev & steam everywhere! No tell-tale water! I hadn't checked when I started it as I was sure it was now completely without problems (won't forget to do that again!)

Turned off pretty damn hot motor immediately. Would restart easily but no tell-tale, but steam being pumped out of exit pipe.

Went to bar in a sulk & had some beer & oysters.

When I went back to boat & now cool motor, started engine & gave throttle a blip & tell-tale was there & cool. Went sailing for a good 2.5 hours & left motor running whole time & tell-tale cool & strong whole time.

If I blow through the tell-tale water pipe bubbles come up through the inlet grills with no blockages. The impeller must be working because the tell-tale is strong & cool when it's not playing up.

I am a bit confused! It seems to me that it is important to give some revs initially to prime the cooling water through.

Is this normal?
Can anyone shed any light on this strange behaviour?

Sorry, I have gone on a bit!

Beautiful sail though, the sea breeze kicked in from the North & we wizzed out of the river at hull speed all the way & returned with the sun-setting behind us. Got a bit of a sunburn though /forums/images/graemlins/smile.gif

 

[DaveNTL]

Sounds like you need to have a look at the impeller. Not a difficult job. You might need to clean it up but far better to replace if you're going to the trouble of opening her up.

One of these would help or you may be able to find step by step online. http://www.iboats.com/Outboard_Engines_M...--view_id.12715

 

[VicS]

Or a question on the yamaha/suzuki board on the iBoats forums. http://forums.iboats.com/

I think the first thing to check is the pump especially if it has not had a new impeller for more than 2or3 years.

But are you sure the pump was properly immersed while you were "getting her ready to go". It is easy to lift the engine too high in a small boat if you are on the foredeck.

If you have run the pump dry it will need a new impeller anyway!

 

[DownWest]

Bom Dia Bife
I second(third) the impeller. You should not be able to blow air backwards through the pump. Bits of mussel might of damaged it? The steam etc. indicates no flow at low RPM followed by reving it and putting cold into a V hot block.
Comprimentos, Andrew

 

[Inselaffe]

Thanks for replies. I had problems again on Sunday, the throttle blip on startup didnt work & I had to suck through the water to prime it, but then no problems motoring about 5 miles bak against the current.
Cracking sail again though!

The impeller hasn't been changed in at least 4 years so I will do this now.

A bit of a pain as the motor is in a well and the high-thrust prop is too big to come through so I have to go in water to take it off first.

Cheers