Single engine position on 26 islander

[Frankie D]

Evenin’ gents
I got a question that hopefully someone here can answer
I have a 95 26 islander with a single Yamaha 250. Granted I feel it’s under powered but I called Grady and they said original performance specs for that set up would cruise at 29 at 3800 rpm and would top off at 44 o believe at 5700rpm. I could deal with that if that’s what I got. But I’m getting 21 at 4700. And maybe 29 at 5700… here’s the thing : theirs is a ton over spray. I trim it out and it’s still there. If i wasn’t getting everything from the engine I wouldn’t get up to 5700, right? So I noticed the engine is mounted at the second hole and think it’s too low in the water thus giving me less thrust and less speed.. I think. Where do you think this should be mounted?

 

[Frankie D]

Hopefully u can see what I’m talking about in the shot
If I can figure how to send video I will

 

[Frankie D]

Not sure if you can see here but it’s in the second ground

 

[seasick]

Lots of things to check before changing the engine mounting. The second hole is the 'factory' default. It is a starting point but just raising the bracket may not help depending on other factors.
You didn't state how long you had the boat and didn't state if the problem was always present. Is the motor a 2 stroke?.
You didn't say what prop you have. That is critical to help determine what is going on. Have you checked the prop for damage, bends and/oy spun hub?
You didn't say if your hull is clean. Growth will slow down the boat.
Is your bilge always wet? Your hull may be soaked. You didn't say if you have trim tabs and what position they are in.
Has the water line risen over the original line? Where does the ventilation plate on the motor sit when on plane?

You also need a new trim tab on the motor. That is not your speed problem but no tab is really bad for the moto.

 

[Automated14]

I’d start with engine height. The anti ventilation plate should be at water level.
The factory and dealers seem to default to burying the engines. I feel like there interest is in delivering a boat that's good enough, not necessarily optimized for best performance.

 

[Frankie D]

Lots of things to check before changing the engine mounting. The second hole is the 'factory' default. It is a starting point but just raising the bracket may not help depending on other factors.
You didn't state how long you had the boat and didn't state if the problem was always present. Is the motor a 2 stroke?.
You didn't say what prop you have. That is critical to help determine what is going on. Have you checked the prop for damage, bends and/oy spun hub?
You didn't say if your hull is clean. Growth will slow down the boat.
Is your bilge always wet? Your hull may be soaked. You didn't say if you have trim tabs and what position they are in.
Has the water line risen over the original line? Where does the ventilation plate on the motor sit when on plane?

You also need a new trim tab on the motor. That is not your speed problem but no tab is really bad for the moto.

sorry if I left out a few details
I have the boat for 2 years and this spray has always been present. it is a 95 yamaha 250 2 stroke. it has a stainless steel prop that i believe is 17 - no damage present. hull is clean and was bottom painted there is minimal growth. bilge is dry. trim tabs are in. pretty sure that ventilation plate is buried when on plane.

 

[Frankie D]

 

[Frankie D]

Tried to get a shot of it running today…
Can’t see the cavitation plate

 

[family affair]

On our old single engine 248, the prop was buried like yours. I think Grady had to do this on all the older, short-hulled, single engine boats to avoid prop "bite" issues. Ours ran similar to factory performance, but the really annoying part was porpoising. We raised the engine one hole. The antiventilation plate was still too low, but the porpoising was much improved.
Our 270 will throw spray if the tabs are used. Are yours functioning properly?

I think I would also get a new tab on there 1st as seasick suggested. That can't be good for water flow.