Over heating outboards

[Pete7]

Rene sent me an e mail asking about an overheating 115 Yamaha 2 stroke, as I used to own the boat. I have decided to reply in public as it might be useful for other ribsters.

"Rene, sorry for taking so long to come back to you I have only just seen your e mail".

Engine over heating is likely to be the rubber water pump in the leg. Undo the seven bolts that hold the gear box on (think the seventh is under the anode/trim tab at the back) Inside and on top of the gearbox is a 3 inch stainless steel cover and the water pump. It is held on with a woodruff key Remeber to put it back on the same way. It was last replaced in 96 if I remember although you had the engine serviced so they should have checked it as its an item of major importance. Also check the two cooling intakes on the leg are not blocked. They are the two balck plastic covers each side of the gear box.

Other causes could be the two temp thermostats on the engine. They are located on each cylinder bank and I think they have a little cover which has 3 or 4 bolts holding it on. they block with salt and stop opening. Easiest way to check them is to put them in a kettle full of hot water and watch them open. Whilst your in there flush down the cooling chambers with the rest of the kettle and perhaps some soapy liquid.

To check the level of the oil is a really messy job. Remove the top bolt (gearbox starboard side just above the cavitation plate). Remove the lower bolt (in the gearbox cone) and quickly (as the oil will run out) put another plastic merc gearbox oil tube in and squeeze. Oil must be filled from the bottom until it comes out at the top to remove any air pockets. Use a drip tray as it goes everywhere!

Finally bleed the oil pump. There is a small brass screw on the oil pump which is used to bleed it if air gets in. Its very soft brass to go carefully. I had to buy a new one in 95! slacken off and turn the inginition on. Oil should flow through without air bubbles. Also worth checking the filters it the small oil tank in the engine, and there might be another in the main tank.

Hope this helps Pete

[Rene]

Hey Pete,

Tanks fore the response.

Here is what I have found out....

I checked the water pump, its not damage in any way. So I'm keeping the old one. I had a Yamaha dealer check the engine, and he told me that there where rust in all the cylinders and that the price for repairing this would be around 2500 Uk pund. I took the top of the engine and the cylinders are like new. But the top gasket has blown, and it's blown right next to the temperatur meter, so I guess thats why it's was overheating.

I have just orderd 2 new top Gasket, new termostats and some other gaskets.

I hope to recieve the last parts from yamaha tomorrow.

The boat is on the trailer, and there is no wind and the sun is shining.

Hope the have the boat back in the water by wednesday. I will let you know what happens.

(I'm woorking like a little beast trying to learn how to put the engine back together the right way)

Regards
Rene

[Pete7]

Rene, good luck. But think the dealer was out to make a few bob. Just as well you inspected them rather than just told him to carry on.

Let us know how you get on.

[batfalcon]

THIS IS THE ONLY WAY to reduce the cost of service of an outboard. If you pay attention to these minor jobs each year, no major damage will ruin your vacations.
The best of it is that you learn by practicing on your engine and believe me, you feel much more confident when you are on your own out there.

[Rene]

Hi Ribsters

Here is the followup on this issue.

Friday I recieved the last two gaskets, to put the engine back together. I meet up with a friend of mine to help out. We changed the top gasket, and put the right torque on it. Then we put on the water cooling top, The first came on right away and seemed to work out ok, but the other side (it's a V4 engine), had 3 bolt,s which didn't get a grip. So we had to drill a bigger hole and make a new thread. To do this, we had to remove the gasket again, and this is a bit special because it's a sticky gasket, so we should have bought a new one, but we tried to put some fluid sealing on and still use the "new" gasket". Then we put it all together. And now It's woorking.

I took the boat out Sunday to test everything, and the temp is steady whether the boat is going slow or fast, and there dosn't seems to be a leak anywhere.

The rpm is within the normal range, from before I had the problems.

But i did bring paddle's just in case.......

If anyone need's some advice on how to do this, feel free to send me a mail.

It's quit easy once you get the hang of it.

Regards
Rene (Outboad mechanic) Nielsen

[Pete7]

Brilliant, nice to see a bit of DIY saving a small fortune over having a dealer completely rebuild a power head. Safe diving, Pete