New prop for Suzuki DF90

J

Jazzmanic

New member
I know, another prop question. After many years of using the stock prop on our Suzuki DF90, which is the 3x14x17, I've decided I want to try a new prop. The current prop is on the bottom end of the RPM's at WOT, 5200. Our boat is usually moderately to heavily loaded, with minimum 2 people. Just the other day, we brought the boat up to around 5000 RPM and were getting about 24 mph on flat, smooth water. The last test I did recently was 5200 @ 26 mph WOT. This is lower than we used to get when the prop was newer. I believe we achieved 29-30 mph @ 5200 RPM WOT lightly loaded on flat water, several years ago.

My question. I'm looking at lowering the pitch to get additional RPM, the range is 5200-5600. It seems that most of the choices would have me drop in diameter to 13 3/4. I'm either considering getting a 3 blade 13 3/4x15 pitch. Would the drop in diameter by 1/4" have a noticeable affect when dropping the pitch 2"?

I'm also considering getting a 4 bladed prop. If I decide to do that, should I stay with the 14 x 17 or also drop down in pitch to 15?

I'm depending on the guidance from the prop gurus on the site to help me with this dilemma. :wink
 
I just bought a 3 X 14 X 15 aluminum prop from Iboats Marine over the net. Reasonably priced and made by Michigan Props. Make sure you specify 4 stroke as the splines differ.
 
We had a 06 Suzuki 90hp 2litre not to be confused with the newer 1.6 litre 90 hp suzuki. we ran a 3bladed S/S prop 14by 18 pitch my boat was a 1999 c-dory cruiser set up for more day trips with twin 18 gallon fuel tanks
top speed was 36mph at 5800rpm cruise nice at 20mph I think about 4000rpm ? Naknek and I had the same motors .Jim
 
Many Suzuki's have a different lower unit gear ration than most of the other comperable outboards. Not sure that this is true with that specific 90 hp.

Yes, going to the 13 3/4" diameter and 15" pitch should bring the RPM up by about 200 RPM. It may not bring up the speed. The big question is why is the boat going slower. My guess is that it is much heavier than when you first started. The usual cause is just putting gear aboard. Fall cleaning out might help. Check and see what is hiding in the bottom of lockers etc different than when you first ran the boat. The 22 with 90 hp should get up about 30 mph. Is there bottom paint--or is there growth on the bottom? The 4 blade will probably not help. The 1/4 inch difference will allow the prop to turn slightly faster, but there will be a slight decrease in blade surface area. I assume that the current prop is aluminum, and may be slightly dinged up?
 
thataway":2ve0c8d0 said:
Many Suzuki's have a different lower unit gear ration than most of the other comperable outboards. Not sure that this is true with that specific 90 hp.

Yes, going to the 13 3/4" diameter and 15" pitch should bring the RPM up by about 200 RPM. It may not bring up the speed. The big question is why is the boat going slower. My guess is that it is much heavier than when you first started. The usual cause is just putting gear aboard. Fall cleaning out might help. Check and see what is hiding in the bottom of lockers etc different than when you first ran the boat. The 22 with 90 hp should get up about 30 mph. Is there bottom paint--or is there growth on the bottom? The 4 blade will probably not help. The 1/4 inch difference will allow the prop to turn slightly faster, but there will be a slight decrease in blade surface area. I assume that the current prop is aluminum, and may be slightly dinged up?
Click to expand...

Wow Bob, are you looking at my prop right now? You hit the nail on every point. Yes, the boat is heavier. Yes, we bottom-painted a few years ago. Yes, the prop is slightly dinged. Good to know about the 4 bladed prop. I guess I'll try either a Turning Point 13 3/4 x 15 or Michigan Wheel 14 x 17.

And thanks all of you for your contributions so far. Keep 'em coming.

Peter
 
Back
Top