Is this engine mounted too low? (pic)

[mswalter2009]

Boat seems to drag over 4000 rpms. Only getting 4500 rpms and WOT and trimmed up.

1984 18 Privateer, 1250 dry weight, 2008 90 hp Yamaha 2 stroke (8 hrs)
Michigan Wheel Apollo Series 13 1/4 by 17" SS prop.

Any help would be greatly appreciated.

 

[Zeeter]

Re: Is this engine mounted too low? (pic)

You are borderline. 4500 will kill that motor. Overpropped or mounted to low. Both may be an issue.

 

[hwsiii]

Re: Is this engine mounted too low? (pic)

Walter , you can come up at least one hole and maybe two holes, but your RPM will still be too low. You will probably gain about 100 to 150 RPM after you get off the double oil. If they will let you bring the prop back trade it for the Yamaha 13 x 17" Painted black Stainless Steel (semi cleaver) and I think your RPM and speed will be just about right.


H

 

[mswalter2009]

Re: Is this engine mounted too low? (pic)

Walter , you can come up at least one hole and maybe two holes, but your RPM will still be too low. You will probably gain about 100 to 150 RPM after you get off the double oil. If they will let you bring the prop back trade it for the Yamaha 13 x 17" Painted black Stainless Steel (semi cleaver) and I think your RPM and speed will be just about right.


H

Thanks for the response!!!
Wow! Spent most of the day emailing / calling the dealer, on forums, researching...etc (not much work work was done) My last call was to the Marine Shop that rigs Privateers. Should have been my first. Ricky said basically the same thing.

Quote:
"Maybe up a hole or two on the engine mount but that wont make up much of the needed RPMs. We install the Yamaha 13 x 17" Painted black Stainless Steel (semi cleaver) Part # 688-45930-02-98 on this exact boat with this exact engine. Get 5500 Rpms. Don't know much about this Apollo prop but since you can't install the standard Yamaha Anode Trim Tab sounds like its a high rake prop, probably with a good bit of cup. The 90 probably just can't swing it to max rpm."

So, the dealer is going to temporarily install the aluminum version and raise the engine up a hole. Hopefully going to test this Thursday or Saturday. I will post the performance numbers on this site.

If I get the the performance I'm expecting then I'll deal with the trade in or exchange for the SS version. They seem to be willing to work with me.

Again thanks for the reply to my post. This site is great. And I will post my performance numbers as soon as I get them.

Just a note - I did do a good bit of research on the prop size / pitch. Mostly from the Yamaha performance bulletins on the web site. The dealer did too and we decided on a 13 x 17 SS. Went with the Michigan Wheel brand because it was "cheaper". I know. Michigan is a popular brand of prop though and I've seen a good many posts here with satisfied users of the Apollo series prop. Hopefully, its just "not right" for my setup. I'm dealing with a 1984 boat that was not designed for the weight of the 4 strokes. Its a waterline to scupper issue.

 

[hwsiii]

Re: Is this engine mounted too low? (pic)

Walter, I have an apollo I use on my flats boat, it is a higher rake cupped prop with a lot of surface area. The 90 HP Yamahas are not loaded with a lot of torque, so it is overpowering your motor and eating torque. When you see the semi cleaver you will understand why I said that is the prop you need, very little surface area and it lifts the stern as well, so a lot of torque is not required. I can't imagine what aluminum prop has comparable blade geometry, I would appreciate it if you would let me know the make and model of that prop when you get it. I am sure you will be very happy with the Painted Stainless. Glad I could help, and I certainly would like to get your WOT RPM and speed when you get everything setup for my database.
And by the way, I don't know what aluminum prop he will put on there, but as a normal course of events you will be able to move the motor up one more hole with the Painted stainless rather than the aluminum, as the semi cleaver likes height a lot.
With the semi cleaver you ought to be running about 38 MPH and have a prop slip between 7 to 11%.


H

 

[mswalter2009]

Re: Is this engine mounted too low? (pic)

Walter, I have an apollo I use on my flats boat, it is a higher rake cupped prop with a lot of surface area. The 90 HP Yamahas are not loaded with a lot of torque, so it is overpowering your motor and eating torque. When you see the semi cleaver you will understand why I said that is the prop you need, very little surface area and it lifts the stern as well, so a lot of torque is not required. I can't imagine what aluminum prop has comparable blade geometry, I would appreciate it if you would let me know the make and model of that prop when you get it. I am sure you will be very happy with the Painted Stainless. Glad I could help, and I certainly would like to get your WOT RPM and speed when you get everything setup for my database.
And by the way, I don't know what aluminum prop he will put on there, but as a normal ourse of events you will be able to move the motor up one more hole with the Painted stainless rather than the aluminum, as the semi cleaver likes height a lot.



H

Has anyone told you "Your'e the Man!!!" I'm sure.

As far as the aluminum prop. That was my idea. I figured they had one in stock that we could test with. If I get anything over 5k then I know its probably not the engine but the setup.

I just spent 7k plus for this engine and installation and my boss (you know the one, ceo and treasurer of the homestead) is asking why I'm taking the boat back to the dealer, what's wrong?, you tell them they will take the prop back or else....) Hard to explain that we bought a $300 prop, installed it and ran it for 8 hours. It's now used. However, the dealer seems willing to work with me on this. On the other hand I gave them the number and contact of the Privateer rigger hoping they would work out the prop and setup before hand. It's not that complicated unless you install a "higher rake cupped prop with a lot of surface area" that possibly is too much for the 90. A simple call by the dealer would have solved this. Live and learn, right?

I just want to see a prop that will quit "lugging" this engine. Between your's and Privateers info its a no brainer that the SS Yamaha prop is the one. It probably needs to be ordered (don't know) but boat dealerships are running lean these days.

Absolutely will update on my performance numbers. Again thanks hwsiii.

 

[hwsiii]

Re: Is this engine mounted too low? (pic)

You are very welcome Walter, and you will be very happy once the boat is setup with the right prop.


H