98 Yamaha overheating.

[Crestcutter]

Gidday fellas i was wondering if anyone can help me out. I have a 98 Yamaha that has just had the heads removed due to it over heating.Turns out the previous owner didn't flush it properly after his last trip and all the salt was blocking the bottom holes in the head.

So i removed the heads and had them sand blasted and bought back to new, fitted new gaskets and refitted yesterday.The guy that sand blasted them said the heads he gave me had good thermostats in them.Yesterday when i reassembled everything agian and fired her i had a heat alarm go off.I turned the motor off for five and kicked her again and it seemed ok.

What i discovered was the tell tale water wasn't getting warm. Is this because the thermostats are rooted. Any help appreciated as this is the only thing i need to sort before i can water test this haines i have rebuilt.

Thanks........Darryl.

[BM]

Did you remove the water jacket covers also? Both sides of the heads will salt up. What did the cooling galleries around the cylinders look like?

The telltale does not need to heat up. Check your cylinder head temps with an IR heat gun if you have one. Should run around 50 degrees.

Yam's salt up like yours has. Its likely nothing to do with the previous owner. They all suffer it at some point due to their narrow cooling galleries.

Toss your thermos into some boiled water to see if they open. That will give you a go-no go answer.

May need to remove the exhaust covers and also clean out the poppet valve.

Cheers

[Crestcutter]

Thanks BM, i haven't got a IR gun , maybe it's me being paranoid. I removed the water jacket covers and they were in good condition.I thought that the tell tale heated up once the thermostats opened? But the heads i could hold my hands on after say around 10 minutes on the muffs. Admittedly one side seemed hotter than the other. I have a plug in for flushing the motor in the middle of the night and ran the motor with the hose attached directly to it and the heads stayed real cool.Soon as i put them back on the muffs she got hot in no time. Does that help.

I didnt do the exhaust cover to inspect the poppet valve so maybe thats where i should be looking. Thanks for ya help mate.

[BM]

The heads should be hot. 50 degrees you can keep your fingers there but it will be a bit uncomfortable. If its burning hot, then its too hot.

The important test is when its running in the water. Take it for a run at full throttle or close to it and if after 5 mins or so its not sounding off the alarm then relax!

Telltales tend to vary a little but they are normally taken from the exhaust jacket. This way there is a telltale from the instant the engine starts (more or less) as its coming from the water exiting the engine with the exhaust.

Cheers

[ozscott]

Gday mate. If you read by thread on my 115 overheating that might be of some assistance (only a few down the page). Hows the impellor? It might not be powerful enough to pump from the muffs. You would be better, as BM suggested, sticking her in the drink and giving her a run (or at least in a big tub of water).

I dont think my telltale heats up from memory - stays pretty cool and I have new thermostats in and a new water pump kit.

Cheers
PS. Good to see that the old girl is not silting up. I dont know if that problem under the water covers is confined to Yammys because my bro in laws Evinrude late 70s model 130 V4 did exactly the same thing - he pulled them and showed me (after he had replaced everything from poppet valve to divertors to impellor etc and it was still overheating at high revs) and the galleys were very narrow and blocked by salt and he cleaned, put back together and no more problems.

[Noelm]

on some models, the tell tale comes almost straight off the water pump (via a hose and T piece) and does not go through the Motor, that is why it does not get hot (but only some Motors) and you mention you have a "hose connection" that you use instead of the muffs? I am not too sure about your exact model, (because we do not know what it is) but some are not recomended to run off this attachment, just flush without Engine running only!

[ozscott]

Yep - I had the feeling that all wash down plugs were for non running flushing only - on all types of engines.

I know that some muffs just dont supply enough volume for some engines. I have had success with muffs but I know some who have not. Sometimes they seal poorly enough not to allow enough water into the leg. The telltale in the Yammy, from memory, does not show what water is passing through the head, just that the water pump is working properly.

Cheers

[Noelm]

Yep, seen some home made muff "gizmos" to help with water supply, some guys buy two sets and take the one with the hose connection of one and add it to the other so, you have two "ears" with a hose connection on the one muffs, and then you use a "Y" piece in the hose to connect up two inlets, that seems to supply enough Water.

[Crestcutter]

I ran the thing on the hose connection for about 2 minutes to see if it heated up.It didn't come off freezing cold. 2minutes on muffs and it was hot. When i unscrewed the hose fitting of the cowel the water in it that ran out was warm??.

Might send it to the mechanics and let him sort it i think.

[BM]

The engine should get quite warm when running on muffs. The thermos are doing their job of keeping the engine at the correct running temperature.

The silent flush fitting is designed to be used when the engine isn't running.

Cheers

[Crestcutter]

Thanks for ya help BM, i will water test it this weekend after i fit my hydrive and see what happens.

Thanks again.