1987 Yamaha 30ELH Overheating - NEW Water Pump, Impeller, Thermostat

[Floater_n'_a_Motor]

Hi Folks, thanks for looking. New to me 1987 Yamaha 30ELH, OIl-Injected with remote steering. It was not pumping water so i installed a new water pump housing, gaskets, plate, cup, impeller, etc. Then i ran it in a barrel and it would pee water, but only at half throttle and above, not at idle. I then backflushed through the motor with a hose, ensured the pee hole and hose were clean. I opened the thermostat housing and saw there was some build up. I removed the thermostat, fed a weed wacker line down in to the motor as far as i could (after it was cooled off), and replaced the cover after installing a new thermostat and gasket. still, it will not pee water at idle. i have to raise the throttle in order for water to come out. The alarm goes off, but i can run it a full minute now before it does. Head is pretty hot when I i turn it off. The half throttle function kicks in as well. What am I missing? Thank you!

 

[Sea Rider]

Was this OB used in salt or fresh water ? If in salt, was it flushed soon afterwords each use with fresh water ?

Happy Boating

 

[Floater_n'_a_Motor]

Just got it. 7 hours from saltwater, likely not. I suspect its the head gasket. Same symptoms after removing the thermostat and placing the cover back on.

 

[99yam40]

If the motor is not sitting down in the water far enough in the tub it will have a hard time sucking water up.

The rubber dampener and dampener support next to water pump could be not sealing due to corrosion of the support bracket. That could let exhaust gasses into the water pump

Or the water tube seals are out of place

 

[Sea Rider]

When head gasket is bad, say hardened, not re torqued soon after break end period ended or over time use, both mating surfaces will not seal properly between them. OB will start to miss when opening throttle, depending on its condition much worse at speed or at full hammer down due to water droplet intrusion on combustion chambers. But being a 31 year oldie, head gasket could already be shot.

If it's a second hand OB probably previous owner used it on salt water for years, do you know anything about it ? If all it's found OK as per 99yam44 recommendations and before replacing head gasket perform a long OB flush on a barrel with fresh water and Salt Away and check if overall temp lessens. If same, replace head gasket and clean all internal water paths, take advantage to decarbonize piston heads, exhaust cover and cylinder head. Will have a new OB purring as a kitten for years to come..

Happy Boating

 

[Floater_n'_a_Motor]

Hi all. Thank you for your input! I went ahead and changed the head and cover gaskets, torqued to spec, and used copper sealing head gasket sealer on the seals prior to assembly. Still the same issue. I noticed the thermo sensor is loose on the head. looked like it was glued in place at one point? i also spent 4 hours cleaning the old gasket material off all surfaces. Still getting the buzzer alarm.

2 questions:
1) when motor is running at idle, it does not **** water very well even with the new water pump housing/gaskets, and backflush. half throttle and above has a strong stream, and not very hot. I can hold my hand on the head for about 5 or six seconds. but the alarm still goes off. could it be a sensor? i did notice that when i raise the idle and the water begins to come out of the pisser, it spurts in an even rythm before raising the idle more and becomes a full stream...

2) why doesn't it **** water and idle? I've done all the back flushing with water and air.

 

[Floater_n'_a_Motor]

i also noticed a rubber tube that sticks out from the lower and runs up along the gear selector rod where it screws together with the lock nut...what is it, and is it suppose to be capped off? ill post a pic...

 

[99yam40]

If the motor is not sitting down in the water far enough in the tub it will have a hard time sucking water up.

The rubber dampener and dampener support next to water pump could be not sealing due to corrosion of the support bracket. That could let exhaust gasses into the water pump

Or the water tube seals are out of place

well did you read what I wrote before?

 

[Floater_n'_a_Motor]

i installed a new rubber dampener when i did the whole new pump housing. Ill pull it apart and check again. they only rubber piece i question is the one the brass tube on the pump fits in to on the upper. the barrel is completely full of water, above the antiventilation fins.

 

[Sea Rider]

There are other internal well hidden hard to reach water passages to have in consideration, If all water paths were impeccable cleaned and the engine has been conveniently flushed on a barrel with Salt Away for at least 30 minutes and the issue continues, replace thermo and heat sensor if having one, one of them or both are not doing its homework right.

There are procedures to check thermo and heat sensor condition, that info should be available on the General Service Manual..When at half to full throttle, is the peeing strong ?

Don't know that particular engine, but all have some sort of rubber grommet that seals upper water tube to lower powerhead side, probably being such an old engine, rubber is shot, dried, water pressure scapes and powerhead does not receive its full water amout the new water pump is delivering upwards, but that issue won't be known till powerhead is removed.

Happy Boating