[mariner45hp]

problem starting my 45 hp mariner when engine is hot

[diaric]

whats it doing when hot? most common is starter wearing out and not working properly when hot

[mariner45hp]

the starter turns and everything. i just have to wait until the engine cools down and it will start again. i noticed the cooling water that squirts out of the engine is very hot, you can see the steam.

[diaric]

thats a cooling issue, but it sould still try to start. when it runs, is there a good stream out of the tell tale? if not the impeller needs changing. if it looks good, then cooling passages could be plugged with silt etc, or a bad thermostat(if it has one). cranking and not starting hot, most likely a coil failing when hot. important to fix the cooling issue first, then see if the starting issue still there or not

[mariner45hp]

there is a good continuious flow coming out, but its real hot. all i have to do is remove the cover let the engin cool down and it start on the 1st or 2nd attempt. it's a 1978 45hp mariner, does that have a termosat? i am not an expert at this, how do i go about fixing the cooling problem>

[diaric]

how many cylinders is this one whats the serial? may able to look up a scematic that shows parts

[mariner45hp]

the serial # is 0B216663. there's four spark plugs, its four cylinder right?

[diaric]

yes, four cylinders, don't see a thermostat listed, so cooling passeges might be blocked. if you put your serial in mercury parts express, you can see schematics of your engine

[mariner45hp]

i don't see anything related to coooling from the pull down menu

[diaric]

neither did i, just a temperature switch. but i looked on iboats under thermostats and didn't see your model listed.
best solution is to remove the lower unit, check the condition of the water pump and impeller. impeller is about 10$ so probably change it. the fins should try to spring out straight and not stay in the curled position as installed. when lower unit is off, you can connect a hose to the water tube and check flow and water coming out of wrong places. if that doesn't fix it, then the exhaust plate or water jacket cover could be removed to check if plugged up inside

[mariner45hp]

i was told that with the serial provided( 0B216663) is a 1978 engine, is that true?

[diaric]

should be 87 or 88

[mariner45hp]

where do i go to find out what year it is for sure so i can get a manuel for it.

[diaric]

someone else maybe able to clarify and give a little better idea of your trouble. mariner years are confusing as there are different serial codes for places of production. if it was a mercury, it would be 1987, the manual is probably the same for both years as they cover multiple years and models