What is the max HP I should buy for my boat?

[critter]

Hi everyone, long time follower first time poster.

I own a 2006 510 Quintrex Freedom Sport which has a 90HP Mercury two stroke (ELEPTO or carby model.

I will be looking at replacing the engine in about 12 months, and given the specials on at the moment in 12 months time I hope they come again. Now here is my problem. The boat is rated to a max HP of 100. So a 100hp command thrust is right down my alley. The motor has a weight of 165kg's. Now the 115 Pro XS also weighs 165kg's. I would love to get the XS but is that possible? Should I just be happy with the 100hp command thrust? Too many options......

Can I get the boat re-plated to the 'weight' of the motor or will I have to be happy with the 100hp?

Help a fella out!

[WildFishExpeditions]

dont go over the max HP to what your boat is rated to. its that simple. it is not just about outboard weight that determines max hp. i had a 510 quintrex with a 75 merc and it went fine, 100hp will be great. your insurance will laugh at you if you ever need to make a claim with too high a HP, might also put potential buyers off when you try and sell it with an outboard too powerful for the hull.

[Skusto]

You can get boats re rated pretty easy if the length of boat to hp falls under the Australian standard, have a chat to prolly a boat builder and they could suggest maybe we're to look.

Most places like quintrex underrate there hulls so as nothing comes back. It is possible and do able most likely but don't think you will gain a heap more top end or anything, from a 100-115 would prolly give you 5kmh more at best for top end speed.


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[critter]

Thanks guys. I had heard that Quintrex do re-rate the boat but not sure on what this might cost. I might 'for the sake of a few more km's per hour' save the extra coupla bucks and get the 100hp and what I save can go towards a boat wrap.

Thanks for the advice again! Cheers and tight lines.

[tarzan]

Mate I had a 510 Freedom Sport with 100hp Yamaha 4stroke. From memory the Yamaha was closer to 200kgs. Performance was great and certainly no need to go beyond the max rating.


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[Flex]

Buy a 75hp Merc, Pull restrictor out and install a 115 ECU(all for the cost of about $1000) and you've got yourself a "highly tuned" 75hp motor Plus saved yourself about $3000..

[Skusto]

Don't forget Yamaha is removing the 80hp and 100hp from there line up and is replacing with there new 90hp.

So there might be some good bargains out there for the 100hp at the minute but once all sold they won't be making them any more.


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[Noelm]

I think it was pretty bad marketing by Yamaha to make those couple of "odd" sizes, every maker has a 70,90 and a 115 but Yamaha decided to go 80/100 not exactly sure of their thinking, maybe to sell up the extra 10HP over competitors?

[Chris Tucker]

You can get boats re rated pretty easy if the length of boat to hp falls under the Australian standard, have a chat to prolly a boat builder and they could suggest maybe we're to look.
Most places like quintrex underrate there hulls so as nothing comes back. It is possible and do able most likely but don't think you will gain a heap more top end or anything, from a 100-115 would prolly give you 5kmh more at best for top end speed.

When companies “under-rate” boat engines when compared to the length x beam calculation in AS1799 it is usually because they are trying to push the limits with regards to passenger numbers and extra engine weight will eat into the allowable weight of passengers. This is especially important because when calculating passenger number you have to divide the max load capacity by 90kg. This means a boat with a load capacity of 450kg can take 5 people but one with a load capacity of 445kg can only take 4 people.

The short of this is that if you get someone to uprate the engine on your boat you might find it will be a bit quicker but you’ll also have one less mate on your fishing trips.

Where boats have been limited in their engine HP due to their proportions it is possible to get the rating increased by applying the ISO standard as this uses the same calculation but only as a starting point and then the practical test to finalise the calculation. The problems with this path are that it will still effect the passenger rating and that it can’t be legally done without the practical test. The result of this is you have to buy (or if you have good friends borrow) the bigger engine and if the boat fails the test you then have an engine you have to return or sell at a loss. You also have to find an engine dealer who is willing to sell and install an engine that is bigger than the builder’s plate allows.

[critter]

When companies “under-rate” boat engines when compared to the length x beam calculation in AS1799 it is usually because they are trying to push the limits with regards to passenger numbers and extra engine weight will eat into the allowable weight of passengers. This is especially important because when calculating passenger number you have to divide the max load capacity by 90kg. This means a boat with a load capacity of 450kg can take 5 people but one with a load capacity of 445kg can only take 4 people.

The short of this is that if you get someone to uprate the engine on your boat you might find it will be a bit quicker but you’ll also have one less mate on your fishing trips.

Where boats have been limited in their engine HP due to their proportions it is possible to get the rating increased by applying the ISO standard as this uses the same calculation but only as a starting point and then the practical test to finalise the calculation. The problems with this path are that it will still effect the passenger rating and that it can’t be legally done without the practical test. The result of this is you have to buy (or if you have good friends borrow) the bigger engine and if the boat fails the test you then have an engine you have to return or sell at a loss. You also have to find an engine dealer who is willing to sell and install an engine that is bigger than the builder’s plate allows.

Thanks Chris. I would rather maintain the number of people safely onboard rather than another 5K's/Hr or so. That's great info guys. Skusto - not really into the yamahas but I might take a look. I was looking at the E-Tec 90 HO but the weight was a lot more and the lower resale??? I love forums like these, gunna make my decisions from here a lot more easier. Cheers.

[ozynorts]

Why are you looking at the command thrust engines????? They are designed to push a big fat heavy pontoon boats not lightweight tinnies.