Sea Rider
Supreme Mariner
- Joined
- Sep 20, 2008
- Messages
- 12,345
If engine/transom optimization works well with sibs/ribs why shouldn't work same on larger boats and engines. A 600 HP 48 footer challenge.
This is an updated 600 HP 50 passenger 48 footer transport boat used mainly to take passengers to off shore faraway places. When we climbed aboard, noticed at a quick glance that all 50 seats are placed way back with included untapped open deck space at bow. Ballance issues.
On our way with (2) 4 strokes Yam 300 HP each at back transom fitted with high thrust SS props, at plane achieved excessive water splashes at boat’s middle side and rear of transom. Plainly noticeable along excessive bow pitching on slight wavy seas cond or while passing on top someone else’s boat wake. Check excessive rear hull drag along rear engine high wake pics.
Being a fan myself of best engine/transom height optimization with sibs/ribs wanted to try my fond sib/rib theories on larger boats and high output engines. The unexperienced boating owner and driver had great headache testing different high thrust props with full loaded 50 passengers on different sea trials.
With owner permission and disbelief raised both engines near 2.5 “with wooden blocks under them, the 50 seats cannot be moved bit forward to better balance the boat at plane, so adjusted both engines with one trim down position. Was currently adjusted at neutral position.
On next outing trial with full passengers load, lateral spray has been reduced considerably, rear water splashes has disappeared and a shorter height water wake has been achieved, combo rides near parallel to water level and bow up & pitching has finally stopped for passengers contempt.
Gained tech facts with current props at wot.
Before :
Wot 5500 rpm/ top speed 43 knots.
After :
Wot 5800 rpm/ top speed 48 knots
Fuel Consumption for same distance :
Before 85 Gal
After 80 Gal
Cruising speed is limited to 5000 rpm at around 35 knots
To end this happily outing must say that just by dialing sweet engine/transom height perfect marriage and better trim position, combo now runs at 5800 rpm of its max wot Yam stated 6000 rpm, has gained extra 5 knots with less 5 gal fuel consumption than before.
This example has confirmed once again that boat builders doesn’t care which engine brand will fit their boats, nor engine manufactures cares onto which boats will have their engines fitted to. So owner will need to resolve this issue by itself if wanting top boat/engine performance throughout the whole throttle range.
Happy Boating
This is an updated 600 HP 50 passenger 48 footer transport boat used mainly to take passengers to off shore faraway places. When we climbed aboard, noticed at a quick glance that all 50 seats are placed way back with included untapped open deck space at bow. Ballance issues.
On our way with (2) 4 strokes Yam 300 HP each at back transom fitted with high thrust SS props, at plane achieved excessive water splashes at boat’s middle side and rear of transom. Plainly noticeable along excessive bow pitching on slight wavy seas cond or while passing on top someone else’s boat wake. Check excessive rear hull drag along rear engine high wake pics.
Being a fan myself of best engine/transom height optimization with sibs/ribs wanted to try my fond sib/rib theories on larger boats and high output engines. The unexperienced boating owner and driver had great headache testing different high thrust props with full loaded 50 passengers on different sea trials.
With owner permission and disbelief raised both engines near 2.5 “with wooden blocks under them, the 50 seats cannot be moved bit forward to better balance the boat at plane, so adjusted both engines with one trim down position. Was currently adjusted at neutral position.
On next outing trial with full passengers load, lateral spray has been reduced considerably, rear water splashes has disappeared and a shorter height water wake has been achieved, combo rides near parallel to water level and bow up & pitching has finally stopped for passengers contempt.
Gained tech facts with current props at wot.
Before :
Wot 5500 rpm/ top speed 43 knots.
After :
Wot 5800 rpm/ top speed 48 knots
Fuel Consumption for same distance :
Before 85 Gal
After 80 Gal
Cruising speed is limited to 5000 rpm at around 35 knots
To end this happily outing must say that just by dialing sweet engine/transom height perfect marriage and better trim position, combo now runs at 5800 rpm of its max wot Yam stated 6000 rpm, has gained extra 5 knots with less 5 gal fuel consumption than before.
This example has confirmed once again that boat builders doesn’t care which engine brand will fit their boats, nor engine manufactures cares onto which boats will have their engines fitted to. So owner will need to resolve this issue by itself if wanting top boat/engine performance throughout the whole throttle range.
Happy Boating
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