Yamaha 140Hp Overheating

Rapson · Jan 16, 2011

I have a Yamaha 2 Stroke 140HP 1987 Model that is overheating. When I cruise at over 4000rpm the buzzer will go off after a couple of minutes. I can cruise under that with no problems.

A bit of history. I have owned the outboard for around 9 months. Had no thermostats in it so I installed some brand new ones (have removed and still overheats). Original gearbox had water in the oil and had a dodgy weld repair done to it and the prop was welded/coroded on and we couldnt get it off with sledge hammers so I found a second hand gear box with a new prop and installed a new impeller with it.

Never had an over heating issue with the old gearbox, only since installing the new gearbox. Got a feeling it could be the impeller but it is brand new and I did have the same impeller on the old gearbox for a short time with no issues.

Any hints on where to start trouble shooting would be appreciated. Going to drop the leg off today and inspect the impeller and go from there. Is it worth taking the cylinder heads off to inspect the water channels?

seahorse5 · Jan 16, 2011

Re: Yamaha 140Hp Overheating

Rapson said:
I have a Yamaha 2 Stroke 140HP 1987 Model that is overheating.

How about a model number since they did not make a 140hp outboard?

SparkieBoat · Jan 16, 2011

Re: Yamaha 140Hp Overheating

yep..they go straight from a 115 to a 150...but just as a general issue..check and make sure the tube fits into the water pump housing tightly and that there are no cracks in housing..

Rapson · Jan 16, 2011

Re: Yamaha 140Hp Overheating

The 140 only came out in Australia, for your info the model number is 140CET0 6F3 UL 751364.

SparkieBoat · Jan 16, 2011

Re: Yamaha 140Hp Overheating

Well then most in here will not be very familiar with that model...but the general steps are still the same..make sure impeller is in good shape and housing is not cracked..then while you have foot down connect a hose to the water pipe and flush the motor good..i have heard of the heads needing to be removed and sand cleaned out of the ports if it is real bad

Rapson · Jan 17, 2011

Re: Yamaha 140Hp Overheating

Thanks for that Sparkie, I will give it a go. The bar I cross (Currumbin) was a bit shallow before they dredged it before summer so there is a possibility of some sand in the system. I think the 140 is very similar to the 150, buggers me why they only released it in Australia?

seahorse5 · Jan 17, 2011

Re: Yamaha 140Hp Overheating

Rapson said:
I think the 140 is very similar to the 150, buggers me why they only released it in Australia?

Is it a V-4 or a V-6 ?

Most outboard companies make special motors for different countries or continents, just like the carmakers do.

pine island fred · Jan 17, 2011

Re: Yamaha 140Hp Overheating

Probably something very simple. When you replaced the impeller, the stainless steel liner in the pump housing became un indexed. There are small ears pressed into it to prevent the liner from rotating. The liner is slightly concentric and will rotate enough to partually block off the pump outlet. Reposition the liner fully in the plastic houseing and do not let it pop up even a slight bit when you are working the impeller in. Am sure that is your problem. regards FRED

triumphrick · Jan 17, 2011

Re: Yamaha 140Hp Overheating

If Fred's suggestions don't get you anywhere, consider that some saltwater motors get corrosion that restricts circulations. Unfortunately, pulling a head and checking is the way to find out..

Rapson · Jan 17, 2011

Re: Yamaha 140Hp Overheating

Thanks for that Fred, you could be on the money there. I do remember the stainless liner moving a little bit when I installed the new gearbox. Didnt get to it yesterday but plan to attack it this arvo. I will let you know the result. Cheers.

Rapson · Feb 13, 2011

Re: Yamaha 140Hp Overheating

Update: Took the leg off and used some gasket goo on the stainless liner to hold it in place, but i dont think it had moved anyway. Motor is still over heating so I might look at doing a whole rebuild of the water pump and see where it gets me.

noelm · Feb 13, 2011

Re: Yamaha 140Hp Overheating

make sure the water pump is ok, but, the most common problem with it overheating when you cruise above 4,000RPM is the water passages will be blocked with salt and crap, seen it a thousand times, the passages are quite small on a Yamaha, it will require removing all the covers and so on to acess the water jackets. The 140HP is a V4 and very common in Australia.

noelm · Feb 13, 2011

Re: Yamaha 140Hp Overheating

OH, and be careful removing all the bolts, you will break some for sure, anything that seems to be really stuck, heat it up before you start snapping them off.

Rapson · Feb 14, 2011

Re: Yamaha 140Hp Overheating

Thanksfor that Noel.
Not really keen to start snapping bolts off in the block so I am looking more at the water pump as I didnt have this problem until I changed the gear box. Pulled the leg off and stuck the hose straight on the intake and had good pressure from the tell tail, better than from the water pump, and water coming from all the places it should.
Dismantled the water pump and it didnt look to bad, except the base plate had some gouges in it that dont look right. Gonna order a rebuild kit and try that so I can rule out the water pump before I start looking at the block.

yamatech43 · Feb 15, 2011

Re: Yamaha 140Hp Overheating

this may help, don't know if you have volvo dealers there....but they have a product called neutra-salt....salt-away is 2nd choice(by far)....the neutra-salt cant be poured in t-stat holes with funnel full strengh and try to get it in quick enough to fill passages...will remove lots of scale and salt buildup....but really you should consider taking the exhaust plate off when an engine is this old...probably just about full of old scale buildup.....have had success with the chemicals but if it was mine....i'd open it up...if three or four bolts break off it's no big deal, you can get plate off over studs that are left and then use vice-grips and small torch to remove...

Rapson · Mar 22, 2011

Re: Yamaha 140Hp Overheating

Update on the overheating issue.

I just put a whole new water pump kit in the leg, new impeller, housing seals etc. Put the boat in a Fingle and headed out to the 36's with out the alarm going off. I though you beauty its fixed until it went off comming in and now its back to just how it was.

I have taken off one of the plates around the head and it looks ok, going to take the other off today to see if there is any obstruction in there.

The lower leg that was on this outboard had a leak in the gearbox and had a dodgy weld repair and Garry amd I couldnt get the prop off with sledge hammers so I got a second hand leg and new prop. The only other thing that is different is the spark plugs are not an exact match to the old ones but I got them from the Yamaha dealer.

Has anyone had anything similar to this problem? It has got me buggered!

seaox20 · Mar 30, 2011

Re: Yamaha 140Hp Overheating

Ive had similar problems with my '89 yam. 200. Sometimes i could run for a while then all of a sudden the alarm sounds. Other times it would not even let me get above 2000 rpms and the motor boggs. Knowing that its either oil or overheating, I cleaned and soaked the carbs, replaced the waterpump, new oil filter(below the main oil resvoir), t-stats, plugs and a new water-fuel seperator. Now i can run wide open for ever and not deal with any overheating issues at all. BUT after coming down from running ( because of a damn manatee zone or a minimum wake area) i idle for about 3-5 minutes and BAM....Alarm

Like yamatech43^^^ said, Try running salt-away or salt terminator which i just bought and running it through the heads. I am trying this tommorow and i will respond with the results. Goodluck SeaOx20 Out

99yam40 · Mar 31, 2011

Re: Yamaha 140Hp Overheating

Have you checked the PRV?
that will cause low RPM temperature problems if it sticks open

Do either one of you have gauges the will tell you if it is oil or overheating?
Just want to make sure you hunting the proper problem area

seaox20 · Mar 31, 2011

Re: Yamaha 140Hp Overheating

i got the original '89 yamaha gauges that are faded and not working. the constant alarm is what told me either oil or overheating. only during idle it overheats

Rapson · Apr 7, 2011

Re: Yamaha 140Hp Overheating

99yam40 said:
Do either one of you have gauges the will tell you if it is oil or overheating?
Just want to make sure you hunting the proper problem area

A previous owner removed the oil pump etc so I pre mix my fuel. After removing the heads I thnk my problem is a small piece that has corroded off the side off the cylinder wall, which happens to be right where the temp sensor is. Could possibly try toge *** welded but I have concerns that it could start a snowball effect with the remaining wall.

Can anyone recomend another fix such as a metal mend type product? I know it will be a temp fix but I dont expect to get to much more life from this engine.

Yamaha 140Hp Overheating

Seaman

Rear Admiral

Captain

Seaman

Captain

Seaman

Rear Admiral

Lieutenant Junior Grade

Lieutenant Commander

Seaman

Seaman

Senior Chief Petty Officer

Senior Chief Petty Officer

Seaman

Petty Officer 2nd Class

Seaman

Cadet

Fleet Admiral

Cadet

Seaman