1978 Mercury 70hp Worth Messing With?

[Mc Tool]

I dunno if your referring to AI , but I think its like a naughty child trying to lie its way out of trouble. If you keep badgering it you can get to the truth .
I was asking about Chinese stationary 9hp motor ...is the 2:1 reduction on the output shaft gear or chain ( its chain ) ,tells me its gear , so I ask if the output shaft rotates the same direction as the crankshaft , says yes it does , so I ask does it have a 3 gear train , answer no it has a two gear train , I ask how that works being that if it has only 2 gears the shafts must counter rotate .........then it tells me its a double roller oil bath chain drive . I had to back it into a corner to get the truth ....I mean I knew anyway but FFS

 

[racerone]

Need to read some better sources of information !

 

[Mc Tool]

Need to read some better sources of information !

what , like here ?

 

[racerone]

Parts book shows a thermostat for 78

 

[Berdink]

Need to read some better sources of information !

It's tough because less and less know what they are talking about. And oddly, unlike you and others here, many talk in absolutes - spouting like they know what they are talking about. I can't figure why moderated forums are losing popularity and Facebook Iz Da Place.

 

[redneck joe]

facebook is NOT a good place to follow a thread or get trackable responses.

 

[Texasmark]

I read somewhere that this 700 only used poppet valves, but I've gotten much more conflicting information on this motor doing research than any of the other motors I've had. I've only owned a 84 Mercury 7.5, a 2010 Yamaha 9.9, a 1984 Suzuki dt75, and the recent 1994 Johnson 90hp.

Poppet valves are pressure activated....by increased water pressure coming from the water pump with higher engine RPMs. If the engine has no thermostat, it has free flowing channels for "limited" circulation at the lower RPMS. If these passages are blocked by corrosion or foreign objects, then you should expect overheating at the lower RPMs (below 2500).

Stats on my Mercs. started opening at around 125 to 142F. With no stat., one would expect the engine block to be somewhere between the temperature of ambient incoming water from the pump and one of these temps. You can't keep your hand on something that's 125F......I can't with tap water in the house that hot. I may have missed it or you didn't post it.....how did you determine that you were overheating at the lower RPMs?

 

[Berdink]

Poppet valves are pressure activated....by increased water pressure coming from the water pump with higher engine RPMs. If the engine has no thermostat, it has free flowing channels for "limited" circulation at the lower RPMS. If these passages are blocked by corrosion or foreign objects, then you should expect overheating at the lower RPMs (below 2500).

Stats on my Mercs. started opening at around 125 to 142F. With no stat., one would expect the engine block to be somewhere between the temperature of ambient incoming water from the pump and one of these temps. You can't keep your hand on something that's 125F......I can't with tap water in the house that hot. I may have missed it or you didn't post it.....how did you determine that you were overheating at the lower RPMs?

I've seen several posts that this motor has issues with overheating.
I was just asking if there was a "fix" to prevent that.