Hi all, Please help ??
So I've had an on/off issue with my Boat Motor. Quick Summary - I believe at WOT I'm getting cavitation that is getting sucked into the water pump intake.
Most all info I can find on the Internet confuses ventilation (Sucking air from the water surface) and Cavitation (Water changing state from Liquid to vapor and back to Liquid due to prop made low pressures at the prop) so finding an answer has been very difficult.
Details, With My Merc Phone Vessel View app /motor connection - 2018 Merc 4s 60hp CT ME60ELPT Long shaft. Engine Starts and gets to 120F and holds steady at idol. I can drive it at any speed UP TO 3/4+ throttle and temps hold at 140f. Short / longer run times - same. 18 Foot 2000 2 toon Pontoon. Current prop - Mercury | Style: 14" Dia. X 11" Pitch - Qa2030x 3Blade
When I get it to WOT 5k+ RPM and Trim up to get best speed - the Temp climbs to Overheat (OH). If I Full tilt down (in) and run WOT it's better, RPM drops a tad due to bow down, to just over 5K and it runs fine at 140f - EXCEPT when I TURN ! left then it climbs to OH.
IT did this 2nd year I had it (not often I do an extended WOT run). And I rarely have the temp / phone app in the boat to monitor ,temp. And I do have cavitation burns on my prop.
So I'm thinking the following possibilities....
Thermostat is 2? years old and I think is OK. (been changed multiple times in the past)
Water impeller is 4? years old and due for a change but I think it's fine ... (low hours only clean Fresh water, no sand/mud, etc.).
Motor's cavitation plate /motor mount height SEEMS to be in correct position height wise - but the engine "Might" go down a little (one hole) - depending on how the holes line up - I might have to re drill if I'm off on the hole pattern. (but even with tilt full in and only when turning I get higher temps ).
I Doubt I'm sucking air (Ventilation) in at the prop at WOT as the Tilt is all the way in - but slightly possible.
I'm thinking that I'm getting cavitation (Water boiling at low pressure at the prop) that may be causing it swirl around the prop and water intake hole and preventing the water from flowing close to the intake holes???
It's said that 4 blade prop instead of 3 blade prevents some cavitation. 13.8" x 11P prop 4 blade .= 4 blade (cross ref to the best prop from my 3 blade 11 pitch).
Any thoughts ?? I have a 13.8" x 11P prop 4 blade on order.
- IS there a good diagram that shows cavitation plate height with respect "two" ponton bottom edges ??
Thanks Greatly !!! SteveC
So I've had an on/off issue with my Boat Motor. Quick Summary - I believe at WOT I'm getting cavitation that is getting sucked into the water pump intake.
Most all info I can find on the Internet confuses ventilation (Sucking air from the water surface) and Cavitation (Water changing state from Liquid to vapor and back to Liquid due to prop made low pressures at the prop) so finding an answer has been very difficult.
Details, With My Merc Phone Vessel View app /motor connection - 2018 Merc 4s 60hp CT ME60ELPT Long shaft. Engine Starts and gets to 120F and holds steady at idol. I can drive it at any speed UP TO 3/4+ throttle and temps hold at 140f. Short / longer run times - same. 18 Foot 2000 2 toon Pontoon. Current prop - Mercury | Style: 14" Dia. X 11" Pitch - Qa2030x 3Blade
When I get it to WOT 5k+ RPM and Trim up to get best speed - the Temp climbs to Overheat (OH). If I Full tilt down (in) and run WOT it's better, RPM drops a tad due to bow down, to just over 5K and it runs fine at 140f - EXCEPT when I TURN ! left then it climbs to OH.
IT did this 2nd year I had it (not often I do an extended WOT run). And I rarely have the temp / phone app in the boat to monitor ,temp. And I do have cavitation burns on my prop.
So I'm thinking the following possibilities....
Thermostat is 2? years old and I think is OK. (been changed multiple times in the past)
Water impeller is 4? years old and due for a change but I think it's fine ... (low hours only clean Fresh water, no sand/mud, etc.).
Motor's cavitation plate /motor mount height SEEMS to be in correct position height wise - but the engine "Might" go down a little (one hole) - depending on how the holes line up - I might have to re drill if I'm off on the hole pattern. (but even with tilt full in and only when turning I get higher temps ).
I Doubt I'm sucking air (Ventilation) in at the prop at WOT as the Tilt is all the way in - but slightly possible.
I'm thinking that I'm getting cavitation (Water boiling at low pressure at the prop) that may be causing it swirl around the prop and water intake hole and preventing the water from flowing close to the intake holes???
It's said that 4 blade prop instead of 3 blade prevents some cavitation. 13.8" x 11P prop 4 blade .= 4 blade (cross ref to the best prop from my 3 blade 11 pitch).
Any thoughts ?? I have a 13.8" x 11P prop 4 blade on order.
- IS there a good diagram that shows cavitation plate height with respect "two" ponton bottom edges ??
Thanks Greatly !!! SteveC
