Avon Seasport performance

[truble]

hey everyone im used to fast ski boats but decided to try a samll rib,,for sum fun,,bought a s/h avon 4.25 seasport with a 60hp feto 2stroke yam,,had a standard 17 alloy prop which found a semi submerged floating stump(teach me 4 going out 1st day after a few days rain) on 1st day out,,did see 103kph on sounder,,and thort shit ey,,this goes ok,,bought a ss sloas 13x 19 and saw 110kph on sounder,,,grabbed gps to check and saw 61.7 knots,@5400 wot..seeing engine was on lowest setting on transom i lifted it 1 hole,,now am seeing 65knots,at 5600rpm@wot,,following tide,,64.6 anytime,,boat luves lots of trim to sit on plank,,and will run 3000rpm b4 popoising,,am going to try 1 more hole up,b4 installing a cav plate dolefin and starting all over again with engine heights,,seems to me small to med size RIB boats do respond to ski boat type setups,,any advice as to porting or carb setups and timing would be appreciated,,cheers all happy RIBBING

[Chris]

65 Knots in an Avon Searider sounds like you may need to check your GPS?

Chris

[BogMonster]

Originally Posted by Chris

65 Knots in an Avon Searider sounds like you may need to check your GPS?

Chris

65kph sounds more like it even that is pretty good!

[truble]

have anuther gps that i use in car,,will take that as well next time then will have 3 speed checkers,,gotta say it dont feel like that speed,,as in the ski boat you knew you was travelling,,and 65ks well i ski at that speed so know its quicker,,anyone know anything about the yammy 2stroke 60hp feto engine,,

[Nick Hearne]

65Knt that is 120kph!!! or 75mph are you having a laugh?
I thought 40 mph was more like the speed!

[BogMonster]

Well I can just crack 40kt/65kph with 115hp so if somebody overtook me with a 60hp outboard doing 65 knots I would be right royally p****d off but at the same time rather impressed

[codprawn]

Check the power to weight ratio. I have a SIB not much smaller than that which does 25mph on a 15hp.

Remember 60hp is a pretty big engine for a 4.25 and it's a true RIB.

Avon = 390lbs
Engine 200lbs
Crew say 170lbs
fuel 40lbs
Total weight - say 800lbs - power to weight is 13.33lbs per hp.

Then compare it with something like a Ballistic with an ETEC 250 - I am guessing about 1400kg or 3080lbs. Power to weight is 12.32lbs per horsepower - not that much different.

Still over 60kts does seem a little high..........

[Johnwin]

The sea sport is a very shallow V unlike the Searider so should be a bit quicker, however, if truble is getting 60+Knots in an over engined 4.25 Avon, fair dinkum

[ribit]

cant personally see that speed from that set up, given the data you supplied, at best around 48 knots, in order to achieve 65 knots you would need more like a worked 26p prop and that's assuming a crazy gear ratio, and that's more than amazing given the type of craft but anyhow happy crazy boating

[thomas]

We dont even get that speed with race tuned 50s on thundercats which weigh nothing and are cats so you have the wind tunnel. I think something is a miss here.

[The Garfish]

Originally Posted by truble

did see 103kph on sounder,

sownder????? dat woz de depf ov worter yew nobbur

Originally Posted by truble

saw 61.7 knots

Originally Posted by truble

now am seeing 65knots

av anuvver tinn ov xxxxx an yewl be up to 67 notts

gaRf

[Jono]

Originally Posted by Chris

65 Knots in an Avon Searider sounds like you may need to check your medication...?

Chris

.....

[ribit]

For those of you that wonder how do you get 65knts...here is what's needed to do 65knts with around 6ohp.......we used to build inshore circuit cats for a particular race series in the early 90,s as you can imagine these were very light, and designed by a famous inshore cat guy to fit into this framework, they had a very special 63hp OMC outboard engine with F1 style gear case on 1:1 with a mini F1 propeller at Windamere it achieved 63knts perhaps a bit more to come if more development work had taken place...so what chance a Searider

[truble]

hey ppl ,,i havent had a chance to take the boat out again this week,,but on those runs i posted i was using a humingbird sounder with >>speed,,and it was showing 120kph at best but 110 seemed easy ,,,then on the 2nd time out i took my garmin gps72 and it was showing 65kn,,at best,,am going for a drive in car soon so will take garmin and check against car speedo,,and next time out in boat will take the navman outa car as well,,,and i agree the speed is really hi for this boat felt about 100ks ,,,but did see hi numbers on gps and sounder,,so thats why i posted it to get feedback form those in the know about these boats,,last few days ive been cleaning up the runner plank as it had sum gouges and needed a re gel coat,,all nice n true flat as had a slight rounding at end of runner plank,,and does anyone know how to get sum more outa these 60yammys,,jetting,,exhaust,,etc,,thanks

[simmons0]

2.00:1 box(a guess)
19 inch prop
8% slip
5600rpm gives 40knots.

[Carrot]

Hi i have a Avon 4.25 sea spot with a 60hp no a very flat day i got 47knots and i thought that was amazing if reading was real

[69cmw]

Resurrecting a 10 year old thread. Is that a record [emoji848][emoji848]

[Carrot]

just look on Google for anon 4.25 sea spot and this was the fist thing dod not look how old it was Sorry . Just thought no way

[beerbelly]

Originally Posted by Carrot

just look on Google for anon 4.25 sea spot and this was the fist thing dod not look how old it was Sorry . Just thought no way

thanks tho funny reading it reminds me when we had mopeds as kids and there was always one guy who had seen 80.6 mph out of his fs1e lying flat on the tank going down a hill (but would never come out for a ride with everyone else)

[beerbelly]

Originally Posted by The Garfish

sownder????? dat woz de depf ov worter yew nobbur







av anuvver tinn ov xxxxx an yewl be up to 67 notts

gaRf