9.8 hp tohatsu

slate1234 · 20 May 2014, 18:21

Hi all I have the above engine (2 stroke) on a 3.2m sunsport v air hull,when there are two people in the boat with light fishing tackel I can get on the pane easey and at 5500rpm, if I add a small child I can only just get on the plane and can't get the engine to rev above 4100rpm I have a standered prop, what prop should I order to use when I have a heavier load that would take me to 5500-6000 rpm.

Landlockedpirate · 20 May 2014, 18:30

You need to reduce the pitch. Stick with the Tohatsu prop, just an inch or so less pitch.

slate1234 · 20 May 2014, 19:30

Ok thank's I have just been out to look at the size of the prop I have it just say's F8.5 so do i just buy a 7.5 ??

SIBer · 20 May 2014, 19:45

I can plane at 3/4 throttle on my 3.3m with 2 adults, 2 x 25kg kids and some kit.
When fully loaded WOT then a passenger shifts back then forward whilst it hops on the plane easily. I use the standard 8.5 prop.

We shift weight to get it up on the plane. You can feel it and the acceleration. I have to back off as 20 knots in a small loaded boat is scary.

Make sure that your boat is up to pressure to.

slate1234 · 20 May 2014, 19:52

yes the boat is up to pressure, the boat fly's with me and a freind around 30 stone (pair of us) and light tackel, but if I add a small child it won't rev over 4100rpm I'm looking to get the revs up, I will change props according to my passengers'

Landlockedpirate · 20 May 2014, 19:55

OE prop range for the 9.8 was 6.5" to 9.5".

I think the 6.5 may be a little too far, the 7.5 sounds good if you only need a little bit of extra help to plane.

Just to add, a 6.5 on say a Yamaha would be classed as a "High Thrust" prop for moving heavy displacement boats about, it may turn into an egg whisk on an inflatable.

AJ. · 20 May 2014, 23:14

7.5 will work I have both depending if I am using the engine on sib or as aux on the RC check out eBay reasonably priced new props on there

slate1234 · 21 May 2014, 16:51

Thanks all for the replys I will get a 7.5 over the weekend and let you know the results

willk · 21 May 2014, 17:18

I'd be interested to hear how that goes - I'm thinking about the same move...

AJ. · 21 May 2014, 17:20

Quote:

Originally Posted by willk

I'd be interested to hear how that goes - I'm thinking about the same move...

Haven't you been thinking about that for over a year now?!!!!!

Take a punt!

willk · 21 May 2014, 17:23

Quote:

Originally Posted by AJ.

Haven't you been thinking about that for over a year now?!!!!!

Take a punt!

Ach, it was winter. I got her out today and she started third pull, half choke - been winterised since late October. Water time on Saturday!

AJ. · 21 May 2014, 17:26

Quote:

Originally Posted by willk

Ach, it was winter. I got her out today and she started third pull, half choke - been winterised since late October. Water time on Saturday!

Wahooo. Yeah think I might bring mine out of hibernation

willk · 21 May 2014, 17:33

And she was looking good - bit smokey but that will be the fogging oil burning off...

slate1234 · 11 June 2014, 18:58

bit the bullet and ordered a 8.5x7.5 prop today should be here friday, I will let you know how it goes I'm hopeing to get out saturday

slate1234 · 13 June 2014, 14:26

So I took the day of work, it's hot calm and life is to short, I got the boat out, engine in the test tank for a warm up and the door bell ring's, it's the courier with my new prop (8.5X7.5), I fitted it with in ten minutes, then invited my uncle to come fishing for a few hours lol he bit, well I can say it topped out at 5900rpm and 14mph on the gps, 11mph was nice and I don't like running at WOT all the time, and it jump's straight on the plane, got five mackrel and two whiting so I am a happy person today,
Thank you for the replys