Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: New prop installed on 1988 90 HP Yamaha
Posted by seanwilmnc on 01/13/13 - 5:00 PM
#1
Back in July I asked for some advise/info on a new prop for my 1988 Montauk with a 1988/1989? Yamaha 90 HP. I went with a Stiletto 13-1/4" x 15" Advantage. . We installed today and what a huge difference. The boat glides along and really has the get up and go it didnt before. I clocked it using my i-phone speedometer app at 37 mph. We had to machine one of the splined washers to get it to slide all the way down the shaft but other than that it was easy to install. One thing I did notice is that my zink trim anode had fallen off. I got a new one and installed it but the clearance from the prop is about 1/4" does anyone know if this is OK?
Posted by Tom W Clark on 01/13/13 - 5:31 PM
#2
Yes, 1/4" clearance is fine. Anything down to 1/8" is acceptable.
But if you ever do have a clearance problem with a zinc trim tab, you can simply grind down the tab down to what you need, or you can buy an optional extra clearance trim tab. Yamaha and Mercury both make several different shapes and sizes to accommodate high-rake propellers.
Posted by msd58 on 01/14/13 - 3:58 AM
#3
I too have 90 Yamaha. It came with a 15" stainless. I found that prop was great for hole shots and skiing but nothing for top end. What RPM's are you at 37 mph? BTW I now have a 17" pitch on boat now.
Edited by Tom W Clark on 01/14/13 - 8:15 AM
Posted by Tom W Clark on 01/14/13 - 8:14 AM
#4
Different models of 15" pitch propellers can yield very different top speeds at the same RPM. Propellers are not generic pieces are hardware that can simply be described by their pitch and the material they are made of. There is far more to propeller design that that.
Posted by seanwilmnc on 01/14/13 - 3:01 PM
#5
Anyone know what sort of top speed I can expect with a 2 stroke Yamaha 90 hp on the Montauk?
Posted by Tom W Clark on 01/14/13 - 3:17 PM
#6
40 MPH-ish. Be sure your motor is mounted as high as it can go when using the Stilettos. That alone will make a huge difference in not only top speed but also how it handles.
Posted by Tom W Clark on 01/15/13 - 8:25 AM
#8
Yes, your motor is mounted all the way down. That is why your boat is so slow. The motor shoud be moved three holes up so that there is a 2-1/4" gap between the top of the transom and the motor mounting bracket "hooks".
o <-- Bolts through this hole? Motor is
All the Way Down
o <-- Bolts through this hole? Motor is
One Hole Up
o <-- Bolts through this hole? Motor is
Two Holes Up
o <-- Bolts through this hole? Motor is
Three Holes Up
Unfotunalty for you, the lower bolts go through the auxiliary bolt holes on the motor mounting bracket (sometimes known as "blind holes" on other models) and the the lower holes in the transom of the boat will need to be filled and two new holes drilled to access those lower slots.
Read this article which describes the bolt hole positions:
http://www.whalercentral.com/articles...icle_id=82