Real world difference between 2.5hp and 3.5hp tender outboard?

[the_branflake]

That's what I was thinking. Even if a bigger (or same but tuned) engine technically offers greater output than the boat can handle, there's no obligation to let rip when half-throttle will suffice...

...so I'm sure I'd rather possess the option to apply more power, even if in practice I never needed it. Buying a virtually identical engine at similar weight that offers 40% more power for only £100 extra, isn't a choice I'd take long to decide.

This upgrade is one of the best purchases we've done. We started with a 4hp 4s, and got the Tohatsu 6hp carb for £90. I was having issues with the last carb so it was even easier to justify the money. With 1 in it makes little different but when loaded that extra power comes in handy, gets the bow up an keeps us dry. Get the 3.5 one day you will want that extra power.

 

[Rigger Mortice]

It's easy to modify the 2.5HP Mariner to get 3.3HP, just extend the slot for throttle lever and cut a little bit off the throttle slide. No change to jets etc. and only difference remaining is the lack of a neutral position. Pretty good chance that your 2.5 - 3.5HP model can be modified in a similar fashion if you don't need neutral but want extra HP.

I don't know which model you are talking about but my 2 stroke would have needed a very different approach. The 2.5hp had a restrictor plate mounted on the carb and a different jet. Changing the slot would have made no difference and modifying the throttle slide would be difficult to say the least.

The current 4 stroke models have F/N gearboxes in both models.

 

[Rigger Mortice]

can i do this for my 2.3HP Honda air cooled ?!

Probably not. My answer about the Suzuki in #15 also applies to the Honda.

 

[Gin]

I bought a Tohatsu 3.5 two stroke just after the importation ban came in, as the engine was a good price and I thought it would do for my Avon Redstart (kept in the cockpit locker ) or my Redcrest (kept at home) or my 8ft rigid dinghy 9ft (kept at the club's boat park) this latter one easily carried 3 adults+ and a load of gear and I thought a 3.5hp would be best.

The two Avons (roundtail inflatables) were OK, BUT it proved to be far too powerful an engine and even with low revs the roundtails would squat down and the engine actually tilt backwards if moderate power was used; the Redcrest coped better but the Redstart was so unsuitable, for with the helmsman in the stern too it was badly balanced- the Redcrest also, but more acceptable.

Of the three tenders, the rigid one managed best but in all truth that did not need a 3.5hp either- a 2/2.5hp would have been plenty in my opinion.

I hope this report of my actual experiences helps you to assess your needs

I should have added that the reason for buying the Tohatsu was that my Honda BF2 (2hp) had suffered a stripped gearbox(impeller failure); that engine was a four stroke and not too heavy and it drove all three tenders perfectly adequately but a gearbox repair was potentially more than the engine was worth.

 

[No Regrets]

The Mercury/Mariner 2.5 would require a different carb (Or the specific internals!) and possibly a new CDi unit.

I mention the CDi because my 2.5hp hits the rev limiter, but doesn't appear to be going as fast as a 3.5hp would, and the Mercury website reckons 1000rpm difference between the two.

Not worth doing, buy the 3.5. my 2.5 was a good engine, despite some reviews you read elsewhere!

 

[Alan_B]

I bought a new mariner 3.5hp 4 stroke a few months ago for my little hunter europa. Great engine, starts very easily, quiet, sips fuel and is grunty enough to push the boat through anything our inland water can throw at us at half throttle. Would thoroughly recommend one. I went for the 3.5 because I wanted forward and neutral. Reverse would be great, but I wasn't prepared to add the extra weight. The 3.5 is about 17kg from memory so easy for one person to carry.

 

[CAPTAIN FANTASTIC]

http://www.boats.net/parts/search/M...OKE) Carb/0R131842 & Up/Carburetor/parts.html

The link shows (i hope) the different parts for the 2.5 and 3.5 Tohatsu/Mercury/Mariner four stroke engine. The 2.5 is the same as 3.5 engine 85cc and approx 1 kg heavier perhaps; the carb jets are definately different, not sure about the cdi unit.