1980 crest/maurell 25'

[99v92c]

Looking for help with my 1980 maurell 25' pontoon. I've lowered the 85 hp v4 evinrude as low as it'll go without drilling more holes but the engine plate well fills with water and the prop cavitates. I've noticed there is a wedge shaped metal piece between the structural rail and the transom/engine pan that kicks the plate lower in the back. Is it possible that wedged piece is pushing the engine lower than it should be? I've attached a photo of the wedged piece for reference

 

[ahicks]

The well filling with water is normal. That wedge doesn't appear to be, but I'm not going to condemn it without seeing a little more of the whole setup, including an angle that allows us to see the position of the cavitation plate in relation to the bottom of the engine pod and pontoons.

 

[99v92c]

This was when I had the engine mounted at the highest hole. This set up would cavitate much worse. Barely off idle it would cavitate

 

[99v92c]

With the engine mounted at the highest hole this is where the engine set in the water

 

[captmello]

with pontoons, you want the motor lower. I'd drop it to the lowest position and see how it behaves. in your second pic, the motor looks too high. what prop are you using?

 

[99v92c]

It is in the lowest position now and still cavitates I'll have to get more photos when I get home. It has a 13 1/4x17 prop

 

[ahicks]

Higher = easier cavitation for sure.

 

[99v92c]

Higher = easier cavitation for sure

It's as low as possible right now without drilling more holes in the transom board

 

[ahicks]

It's as low as possible right now without drilling more holes in the transom board

Understood. The question remains, is that low enough? This being a 1980 boat, it appears there's a good chance that engine pod has been changed. My experience, which dates back to the era this boat was new, was that VERY few late 70's, early1980's boats had enough engine pod to carry 85hp motors. Betting it's been changed, leaving the question, did they know what they were doing?

 

[captmello]

If it were me, I would pick up a different prop, that small diameter 17p seems like a terrible choice for that boat. do you have a tach? I have a similar size boat and motor and I'm running a four blade, 13p prop that has served me well. as stated, you may be forced to rework your pod and transom in the future, but I'd switch props now. you may find it helps quite a bit.

 

[99v92c]

If it were me, I would pick up a different prop, that small diameter 17p seems like a terrible choice for that boat. do you have a tach? I have a similar size boat and motor and I'm running a four blade, 13p prop that has served me well. as stated, you may be forced to rework your pod and transom in the future, but I'd switch props now. you may find it helps quite a bit.

I will definitely look into another prop. I installed an omc tach but it shows to idle at 3k so I think I was sold a faulty tach

 

[99v92c]

Do I stay with the same diameter and just get a lower pitch?

 

[captmello]

diameter doesn't matter as much as long as it fits. I think mine is around 14.5ish.

 

[captmello]

I will definitely look into another prop. I installed an omc tach but it shows to idle at 3k so I think I was sold a faulty tach

you might have to switch the setting on the back of the tach...

 

[99v92c]

you might have to switch the setting on the back of the tach...

I did. It was at up for an 8 cylinder. I switched it for a 4 but still is not accurate.

 

[99v92c]

This is how it looks with it lowered all the way down

 

[ahicks]

This is how it looks with it lowered all the way down

You need to take that shot again about 6' - 8' further away. It's difficult to get any perspective in this one. Would be nice to get a shot showing where the engine cavitation plate height is in relation to the pontoons.

From what I see here, it's pretty high, but it's tough to see for sure. And just as an FYI, it's not at all unusual for the pod to have an inch or 2 of water in it at rest. Maybe more at low speeds/heavy loads....

Cupped props generally don't cavitate as easily.

 

[99v92c]

Does this help a little?

 

[ahicks]

Sure, that's great. From that pic, it LOOKS like height should be OK, but it's certainly not too low.

 

[99v92c]

I might have to try to get it lower. The bottom of the engine pod diverts so much water when the boat gets going that you can see the top of the cavitation plate above the top of the water. So I think I need to remove that wedged piece or get the engine lower