Yamaha 75Hp 4S Motor Hieght..What hieght is correct?

[LuvMyLabs]

I've completed my 10 hour break in and want to start tweaking my set up with prop & motor hieght. I'm not concerned with getting evey last mph out of my Alaskan (not the boat for that) but do want to make sure it's set up properly for most effiecent operation.

Motor Hieght Question:

I had the motor raised to the second hole from the top because it sounded like it was working very hard at full throttle and I couldn't get any bow lift. Also, the anti-cavitation plate was completely below the surface no matter what trim I set it to.

Still it's under water with 0 trim on plane but I can see it if I do about 1/2 of the available trim level.

Performance Question:

Prop: 3 Blade Yamaha Aluminum 13 1/4 X 17-K

I believe I'm pretty much where I need to be. I'm running 36-38.5 mph @ 5900-6000 WOT depending on conditions and boat load.

I just feel I should be getting more bow lift. When I have more wieght in the bow. I pretty much need to do full trim to get the bow up and at most only the front 50% is out of the water.

I'm not sure is if this just how 18' Lund Alaskans run or not.

So I guess my long winded question really is.

How do you know when you have the proper engine hieght, should the cavitation plate be just above the surface of the water when on plane and not trimmed?

AND

Should I need full trim to get my bow out of the water with a light load in the bow?

[outdoorsron]

Hello LuvMyLabs : You might just have to raise your motor on your boat and see what happens.Possibly raise it all the way up and find out what happens. then lower it to see where the best mounting spot is for your set up. I just don't think that a certain setting that works for one guy is best for all. Also prop selection makes a difference. When I started working on my boats engine height and prop selection it was like vodoo and smoke and mirrors. I kept playing with it but was finally satisfied with it. Also put your equipment ,1/2 a tank of fuel, and fill the livewell for testing purposes to give your boat an average load to see how it performs. Good Luck O R

[Nimstug]

Same motor and prop on my 16.5' Alumacraft and about 1 mph less than what you get. You've maxed out the rpms. Personally, I wouldn't move the motor. I'd bet you a dollar you'll end up back where you started. I think mine is bolted one hole from the top but we're talking different hulls.

For efficiency, run at about 3800 rpm, this Yam's sweet spot for 'mileage.' You'll be running a bit less than 25 mph.

Get as much unneeded weight out of the boat.

Nimstug

[propmann]

Originally Posted by LuvMyLabs

I've completed my 10 hour break in and want to start tweaking my set up with prop & motor hieght. I'm not concerned with getting evey last mph out of my Alaskan (not the boat for that) but do want to make sure it's set up properly for most effiecent operation.

Motor Hieght Question:

I had the motor raised to the second hole from the top because it sounded like it was working very hard at full throttle and I couldn't get any bow lift. Also, the anti-cavitation plate was completely below the surface no matter what trim I set it to.

Still it's under water with 0 trim on plane but I can see it if I do about 1/2 of the available trim level.

Performance Question:

Prop: 3 Blade Yamaha Aluminum 13 1/4 X 17-K

I believe I'm pretty much where I need to be. I'm running 36-38.5 mph @ 5900-6000 WOT depending on conditions and boat load.

I just feel I should be getting more bow lift. When I have more wieght in the bow. I pretty much need to do full trim to get the bow up and at most only the front 50% is out of the water.

I'm not sure is if this just how 18' Lund Alaskans run or not.

So I guess my long winded question really is.

How do you know when you have the proper engine hieght, should the cavitation plate be just above the surface of the water when on plane and not trimmed?

AND

Should I need full trim to get my bow out of the water with a light load in the bow?

The prop that you have is a sternlifting prop if you want more bowlift you'll need to get a different prop. Most of the times you need to go to a ss prop to lift your bow.

[LuvMyLabs]

Hi PropMan,

Thanks for the reply..set you a pm

[Lunddude]

Same boat different motor as mine.

I moved my motor up 2 holes so it's now on the 3rd hole from the top & my cavitation plate is now up out of the water when running where it should be. I don't think you'll be able to go up another hole with out having that Yamaha semi cleaver prop of yours blow out on you.

When I run my Solas 15P I have good bow lift & my boat is the SC model. When I slap on the Quicksilver 17P which has more rake & cup then the Solas, I use very little trim to get the bow up and out of the water.

With the QS prop I'm only running on the back 4' of the boat. I think you would be suprised if you raised your motor up 1 more hole and went with a different prop.