Updates :
As the owner was a bit reluctant to get my hands on his engine he finally agreed due to such awful water performance he was experiencing lightly loaded. What was found :
-The NGKBPZ8HS-10spark plugs were so badly torqued when changed that with a strong hand turn came off, were found extremely darkened and fouled. The plan was to install 6 new ones in, but weren't locally available. So brushed them off after a long soak in paint thinner, checked the current tip gap, were found with 1.2 mm, so re gaped them to 1.0 tight.
All 6 spark booth's and 6 ignition coil outputs contacts were found grubby and bit rusted, polished them to shinny factory conditions with a Dremel metal brush set at slow speed. When performing motor services both ends should be inspected and cleaned, polished, whatever needs to be done, the motor will work much better.
A Compression test showed 118-120 PSI on all 6 cylinders, so good to go according to tech specs. Made a spark intensity test with a bulb type tester, all 6 ignition coil outputs lighted strong bluish. BTY this tester has a large filament inside a translucent container which lights bluish in the whole filament's extension if the output is strong enough as I could feel when receiving strong shocks while holding the tester. LOL!!
Once combo was on water, a slight turn of the key turned on the motor instantly roaring strong at idle, the cleaned spark plugs, well gaped, with shinny cable's ends accounted for that. After a 3 minute warm up time went for a wot run on flat calm water conditions and with 2 up the motor just revved at 5 K which is still low revving at the lugging side of the wot rpm range which is 6 K.
Question: If going for same prop type as current 3 blade 19 one for say a 17 pitch will the motor rev up towards 6 K ?
On last outing some weeks back to a far away place while experiencing rough, choppy, white capping, swells water conditions the motor went into the slow mode, impossible to rev higher than 2 K, when encountered flat waters the motor revved normally at wide open. What could this condition be due to ? The main oil tank was near full same as the internal small one. This motor needs to have a close thermostat inspection, current ones should be rusted, salted. For peace of mind the owner will order 2 new ones along 6 new NGK spark plugs and a less pitch prop if the prop experts suggests it's the way to go...
Yep, that tank has an internal water filter and a lower side drain valve, must the water colected there need to be drained periodically or the motor's system will alert so if capable doing so ? The fuel pump is housed there to be cooled with the internal water, right ?
