'99 272 Saillfish buried prop

[Tucker]

Gents,
Can't see the cavitation plates. Believe the engines need to go up a hole. Currently on 3-hole. Is raising the motors going to appreciaby increase speed & efficiency? Looking at a pretty big job: Rent engine lift, spend a day digging out 5200 from lower slots and around bolts, and pray the pop loose. Probably looking at a days work for the DIY'er. Right now I'm at 3800 RPM 28 kts cruise and max at 41 kts 5400 RPM.

 

[Cocoliso VI]

Gents,
Can't see the cavitation plates. Believe the engines need to go up a hole. Currently on 3-hole. Is raising the motors going to appreciaby increase speed & efficiency? Looking at a pretty big job: Rent engine lift, spend a day digging out 5200 from lower slots and around bolts, and pray the pop loose. Probably looking at a days work for the DIY'er. Right now I'm at 3800 RPM 28 kts cruise and max at 41 kts 5400 RPM.

Tucker do some preliminary checks before you start the project. The anti-ventilation plates are normally 1 -2 inches above the bottom of the hull. Check this with a straight edge and see how they are mounted. If the engines are mounted too low you should get an increase on top end and efficiency but don't expect huge changes on your numbers they seem pretty good already. If you go too high you might get porposing or the props will loose bite on sharp turns and following seas. Are your motors on a bracket or transom mounted on the 97 Sailfish? Brackets allow for higher mounted motors.

 

[Tucker]

Motors are transom mount. What hole you on with your 4-strokes Coco?

 

[Cocoliso VI]

Good question, nut sure either 2nd or 3rd ventilation plates are about 1" above hull. I run similar numbers to yours with 19" pitch props. Mine will sometimes ventilate in following seas but not in turns.

 

[Tucker]

I'll lose bit in a mildly sharp turn. What year is your boat? I think you're sitting a little lower in the stern than me. My OX66's weigh in at 538 Lbs each. I bet you're up a hole higher than me.

 

[bayrat]

Something isn't adding up. The fact that the anti vent plate is buried indicates that you should raise the engines..but the fact that the boat breaks loose in sharp turns says the height is ok and raising it up a hole will make this problem worse. The theory is that if you are trimmed properly for the most efficient running straight, then it's not abnormal to slip a bit in a sharp turn and this is taken care of by trimming down a bit in the turn. Are you perhaps running the boat trimmed up a lot to gain rpms? That's the only thing that I can think of that would make this happen while the engine is mounted too low. Agree with Coco that you should do a little more investigating before you plunge into this. My plate was buried too. I had mine raised by one hole and really didn't notice much difference, but if you're not getting max wot, you should see some added rpm's. I was already achieving max wot before that but I did notice boat was easier to steer and therefore more responsive. I have to raise it one more hole as the plate is still underwater which definitely causes drag. Sort of like when you stick your hand out the window of a moving car...if you dont hold it exactly level, the wind takes it. Thats what happens underwater with that plate and thats why they say it should be on TOP of the water. Try running it with less trim next time and see if you still lose it in sharp turns..if you do I would be skeptical that raising it will give you what you want....if you dont break loose, then I would go ahead and raise it. Hope this helps.

 

[Cocoliso VI]

Tucker my boat is a 2002 Sailfish. I'll check the height on my motors next time i'm at the marina.

 

[Cocoliso VI]

Motors are transom mount. What hole you on with your 4-strokes Coco?

I was at the marina today. Motors are mounted on the second hole from the top. Ventilation plate is 1" abovve the bottom.