Best size prop as we have no idea!!

ajg74 · 12 May 2010, 17:37

Could some kind soul please advise me, what the best prop would be to use on a 5.3 Ribquest with a Susi DF90, twin console with forward seat in it,a 75 litre in console tank and rear 3 seat bench, we have no idea what the one thats on it at the mo is but about 30.5 knots is the fastest the Garmin has showing on it and we haven't managed to improve on that, it is rather quick out of the hole so I suspect its not got a large pitch on at the mo, we think more top end and less get up and go would be best, we tend to mostly be 3-4 persons onboard, I've heard that as the older DF90 (2004) has a lot of low down grunt it can take a pretty large pitch?? Cheers!

Nos4r2 · 12 May 2010, 17:50

What revs is it doing at full throttle?

ajg74 · 12 May 2010, 18:01

it will rev to 6k if you let it, easily, so am thinking its very under prop'd

Nos4r2 · 12 May 2010, 18:52

You need to go up around 4" at a guess. Maybe more though if you're hitting the rev limiter.

What's the prop on there now?

ajg74 · 13 May 2010, 14:04

No idea at the mo and the boat is in its storage home at the mo, I kind of remember the guy who sold it mentioning 15" though which I'm sure is too little for such a set up? Will have a look at it next weekend hopefully when we start prep'ing her for next bank holiday weekend! Another dumb question but with what other make of motors are Suzuki DF90's props interchangeable with, ie Yamaha etc?

Nos4r2 · 13 May 2010, 18:46

Quote:

Originally Posted by ajg74

No idea at the mo and the boat is in its storage home at the mo, I kind of remember the guy who sold it mentioning 15" though which I'm sure is too little for such a set up? Will have a look at it next weekend hopefully when we start prep'ing her for next bank holiday weekend! Another dumb question but with what other make of motors are Suzuki DF90's props interchangeable with, ie Yamaha etc?

Buy a Suzuki prop to start with so you've got a baseline from a standard,known part.. If he said 15" that'd make 19" about right, which would generally be around the right size for a 90hp anyway.

samt · 13 May 2010, 19:15

Is this any use to you?

http://rib.net/forum/showthread.php?t=35747

The box says DT75, DT90, DT115, DT140.

I'm not sure if it fits the fourstroke range. But somone on here might know...

Downhilldai · 14 May 2010, 12:46

The older DF90 has a 2.59:1 gear ratio, so you'll need a coarse pitch prop. 15" is waaay too low. I'd suggest you start with a 19" or 21".

Ribcraft have rigged a lot of their 5.3m RIBs with DF90 motors, so perhaps a call to Jason, Dorian or Charlie at Ribcraft will get you some info on what props they have used on their boats.

ajg74 · 14 May 2010, 17:38

Cheers for all the replies on this guys, I think we might be going to check a few things on the boat this weekend (as its stored 30 miles away!)so I'll have a look at the prop thats on it if we do, I like the sound of a brand new one for 45quid!!

Erin · 14 May 2010, 17:55

I had a 19" on my DF90 on a 5.8 boat to start with then went up to 21. I'd suggest you try a 21.

ajg74 · 14 May 2010, 21:08

Well it turns out its got a 19 on it already, the spare one is a 15 (ie useless really!), 21 it is then, when finances allow, the tow car is due a service first!! lol

Nos4r2 · 15 May 2010, 01:51

What's the make of the prop on it? It's not plastic by any chance is it?

Erin · 15 May 2010, 09:45

Quote:

Originally Posted by ajg74

Well it turns out its got a 19 on it already,

Is it the right diameter. Sounds like it may be too small.

ajg74 · 17 May 2010, 11:50

I'm going to have a proper look at it next weekend, as I said though the tow car os due a servcie so the prop will have to wait now, will just file out the couple of small nicks (which where in it when the boat was bought) and it will have to make do for now, cheers for all the responses though guys!

GINGERIB · 21 July 2010, 18:42

Quote:

Originally Posted by ajg74

I'm going to have a proper look at it next weekend, as I said though the tow car os due a servcie so the prop will have to wait now, will just file out the couple of small nicks (which where in it when the boat was bought) and it will have to make do for now, cheers for all the responses though guys!

Hi, Did you get further with this? I have the same engine on a 5.3 ribcraft with a 3x14x19" ali prop, max speed is 34knts at 5900 revs and would like to increase the top end speed if possible as mainly using rib 1 or 2 adults for fishing and dashing across the bay.