tohatsu outboard probs

[355avk]

hi all i recently brought a 2nd hand 4.45mtr with a 97 model tohatsu 50hp,when i brought it i noticed it wasn't pumping alot of water so i put it in for a 12mth service and they replaced the thermostat,new water pump housing and impeller,picked it up yesterday and took it to the ramp and it pumps plenty of water then when your at wot it stops pumping?took it down again before and pumps fine all the way to 30kph anything over that it stops pumping so i'm stumped on what it could be:-[.

any ideas on what it could be would be appreciated.

i wont be going back to where i got it serviced again.

[Spaniard_King]

Possibly a water pickup problem, check to see the intake grates are on the right way to promote water flow into the gearbox housing.

[outboardstogo]

hi there could be a bit of the old impeller or something similar blocking the tell tail outlet.
at high revs is when it has the most pressure in the water cooling system so maybe its trying to push it out the little hole and therefor not pumping .
i dont think you have to worry about it doing damage to your motor as there will still be plenty of water being pumped through the system.
if you are worried you can fit a water pressure gauge better than a teltail anyway as you can see it on the dash all the time.
if you can get someone else to drive the boat at wot and then have a look at the exhaust relief and see if there is still plenty of water coming out.
the only other thing it could be is that the cooling system isnt holding pressure when the block is hot and has full water pressure due to the water escaping either through the cylinder or though a hole due to corrosion internally or even a dodgy gasket.
does the motor run a little rough or bog down (lose a little power)at any time

[355avk]

thanks for the replys,the engine isn't bogey or slugish,its got 140psi in all 3 cylinders,i think there maybe a blockage or build up of crap in the waterjackets,is there any thing i can put through it to unclog it?like the stuff you can put through a car radiator?

[dreemon]

Try pulling the hose off where itgoes in to the motor and start it and see if water pumps out then, also after it's been running place your hand on the head to test if it's getting hot, you should be able to hold your hand on it for close to 10 seconds, have a look at the thermastat too, good luck

[dnej]

355 AVK,
The water pressure gauge is the ducks guts. I would have one fitted, as you then know for sure, regardless. If you pick up some sand , and have a blocked tell tale, you still know if you have water pressure. I installed mine myself
David

[dnej]

Water Pressure Meter

http://www.tohatsu.com.au/images/acphoto043.jpgMonitors your cooling water pressure. Includes vinyl pipe and installation hardware
Parts Number
Description
3E0-72527-0
Water Pressure Meter

http://www.tohatsu.com.au/accessories-gauges.htm