Performance Enhancement

[MIKOS]

Hi Guys,
First day here and first question.I own an 3.8 allycraft tinny 2002 with a 15 hp mercury (tohatsu) and the total weight is approx 250kg.It goes great at the moment but when it is early in the morning with glassed out conditions i want that extra top end.Ihave thought about upgrading the propellor to stainless.will this improve the performance by much or am i better off using that $350 for the propeller and putting it towards a new motor.If going for the new motor would 30hp be too much.

[Tracker]

I think 15hp on a 3.8 would be about right. more hp means more weight on the bum and at that size not a good thing.
cheers ;D

[basserman]

not sure of your boat however i have a 3.85 explorer throphy with a merc 25hp and although that is a great little motor if i had my time again i would of gone to a 30hp as i think that would be the best size motor for these size boats
by the way my max rateing on the quinny is 25hp

[DaveSue_Fishos_Two]

Welcome to the site Mikos ;)
Go for the bigger motor, IMO. 25 or 30 would be great.

Cheers
Dave

[MIKOS]

Thanks Guys,Max Rating is 25hp Thinking about the merc 30 (tohatsu)
Its supposed to be a light weight model about 10 kg heavier than the one ive got.Look out fishies. ;DBuy The way I have followed this site for quite some time and am looking forward to talking some more to you guys.Cheers

[dugong]

go the tohatsu 25hp and when it has its first service have the restrictor plate removed from under the carby, hey presto ;D its now a 30hp. 8-)
i was told this by my local tohatsu dealer.
cheers

[youngfisho]

you say the max rating is 25hp yet you are keen to put a 30hp on the back. Weight is not the only issue when it comes to hp ratings. Too much hp and the boat can be dangerous to drive. A number of mags have recently published an incident where a person in a 4m tinnie was towing a tube with a 50hp 2 stroke the hull was rated to 40. The boat subsequently flipped from having too much power when it wasn't needed. A mate of mine has a 3.8m bermuda with a 25 yammie cv, used to have a 9.9 mercury. Which he says he is more than happy with the power. Doesn't need as much throttle to get it moving and the increase in weight wasn't much of an issue. As far as props go you'd be looking at around the 500 mark (i think) for a stainless prop. but changing the pitch and diameter will have more of an effect on top end than the material that it is made of. Also stainess props have less give (due to their strength) and therefore any object hit underwater transmits through to the gear box causing damage



andrew

[Bosunsmate]

Firstly, a Warm and hearty WELCOME........

After discussing this issue with a neighbour who just happens to drive a blue taxi ( I was going to do the same thing myself) I would offer you the following advice......

Don't go over the Max HP rating, if either the Fisheries Patrol or the Water Police stop you and pick it up, you WILL be fined and have you vessel ordered OFF the water..............could make for a very very expensive couple of extra horsepower......Go the 25 and put a foil on it.......should get up and keep you legal... :)

I have a 3.6m glass runabout with a 25/2stroke Evinrude with a hydrofoil fitted that gets me up onto the plain at about 1/2 stick with two up and full gear.

In the end its your choice but IMO stay legal and stay safe......... :)

[Needmorerum]

I've got a V-Nose Punt (Stacer Proline Angler) with a 30 Merc on the back. It's great. Pegs along with one person in it at a touch over 40kph, and doesn't lose to much with two in it.
Just spent the weekend away and had 3 blokes in it and it gets up and goes well. The Merc's are a really torquey motor and I reckon are the ducks guts.
Obviously my opinion, others would and I guess will disagree. Maybe a pitch change is what your after, but if your looking for an all round package, go for the motor upgrade. But as said, keep it all legal, turns into an expensive fishing trip it you don't.

Corry

[MIKOS]

Thanks Bosunsmate the advice that you and corry have given me have certainly got me thinking as safety is my number one priority ;).what if i do what dugong says and go the 25hp and remove the so called restrictor plate can this be still classed as a 25hp even knowing that only i will know it is now a 30hp 8-).the motor will still be badged as a 25hp.As for a 50 on a 4 meter tinny no way that seems seriously overpowered.but then again when you are all loaded up to go away on the weekend the extra power is great.but like previously said now i know its illegal so I will be staying away From the badged 30Hp :)

[basserman]

you can have overrated motors on the boats the only things you will need to get done is have the maker of the boat give the ok and re rate your boat and secondly if insured let the insurace compaine know and it will be up to them if they will then insure it

i have inquired into uping my 385 qunny to a 30 2stroke and that is fine by them
so if you really did want to go and do it it can be done but like most things you need to go and do a bit of paperwork first ;)

[MIKOS]

Hi Basserman,The main reason for an upgrade is to get that extra top speed but only when the conditions are right.Also handy when you carry alot of gear and you want the motor just to be ticking over and not having to rev the guts out of it to go places.Have certainly had some good advice on this one.here is a piccy of the motor.I think ill be doing some wheeling and dealing at the boat show coming uo.Cant wait

[MIKOS]

woops will try again later

[Bosunsmate]

What restrictor plate........... ::) ;)

What they don't know wont hurt........it would only be found out if there were a serious accident and the motor was subject to tech inspection....

[New_fisher]

Guys does anyone know the difference between the 40 and the 50hp Yamaha 2 stroke 3 cyl? Is there a restirictor plate or is it to do with the carby jets/exhaust manifold? I take it they are the same core engine - they look the same, any ideas? Cheers fellas.

[blaze]

I dont know but would have thought it would be more complexed than just a resrictor plate, for example- if you resrict air flow there is no need for the same amount of fuel.
cheers
blaze

[MIKOS]

Maybe a different carby. I think that once you start stuffin around with engines as we all have done (cars included)there is always the reliability factor.Dont think id like to go here.Might do what basserman suggested and get it approved to go the thirty [smiley=2thumbsup.gif]Cheers for the feedback

[Fishin_Dan]

With the Evinrude 40-50HP difference, I think (From memory of what the techo said) was different carbies & linkages. Otherwise the same motor...

Someone like Spaniard King would probably be better answering this one though...