Mercury sportjet90 disassembly

[Crater]

Has anybody ever disassembled a Mercury sport jet 90 power head?
I must have some gravel or sand up in there causing mine to overheat after running wot for 20-30 min then coming back down to idel the warning buzzer sounds. I've tried to flush it out serveral times but it still does it. Dad has a 75 Force that had to be disassembled and cleaned for the exact same reason. and since this is a Force block I figure I'm in his shoes now but I don't have the $750.00 it took to clean it. So if anyone has any idea has to the disassemble (as to, should I take the exhaust manifold off first or the head off first?) advice I'd sure appreciate it.

 

[hondon]

Re: Mercury sportjet90 disassembly

First of all ,do a compression test on this unit to make sure that no internals have been damaged with all those sporatic overheats.Next check the intake for any backed up gravel or sand that may be restricting water flow and backflush those lines.This is a Force powerhead so the specs will be similar if not identical.A factory manual would come in handy now but this is a project that Merc would would just as soon forget in in it's early incarnations.

 

[Crater]

Re: Mercury sportjet90 disassembly

Compression tests are good 120psi on all 3
Have mercury man. it only tells what the causes of overheating maybe.
Clymer has motor dia. But I just thought if anyone has had to do this maybe they could save in some extra work and $$.
Mech. that worked on dads said the water passages were some small the almost anything in there might clog it up.
How about a flow chart for the cooling system?