Go faster outboard.....!

[Ammonite]

I can't remember who it was but many thanks to the forumite who described how to turn your 2.5 Mariner 2 stroke into a 3.3hp by modifying the carburettor, chopping about 6mm off the throttle valve and increasing the slot in the fascia so the throttle can fully open. I was bored one weekend and decided to give it a go and now have a veritable speed boat! OK its only 0.8hp more but it made a surprising difference. Took me right back to my Mini tuning days as a kid. Small things please small minds I guess

 

[jac]

I can't remember who it was but many thanks to the forumite who described how to turn your 2.5 Mariner 2 stroke into a 3.3hp by modifying the carburettor, chopping about 6mm off the throttle valve and increasing the slot in the fascia so the throttle can fully open. I was bored one weekend and decided to give it a go and now have a veritable speed boat! OK its only 0.8hp more but it made a surprising difference. Took me right back to my Mini tuning days as a kid. Small things please small minds I guess

Have you got the details of that? I have a Tohatsu 2.5 2 stroke and have a feeling that it's the same engine as the Mariner.

 

[Ammonite]

Have you got the details of that? I have a Tohatsu 2.5 2 stroke and have a feeling that it's the same engine as the Mariner.

Couldn't be easier but I know that the jet in mine is exactly the same as the 3.3 - worth checking with someone who knows. All you need to do is remove the cowel and fascia panel and look into the carb. You will see that when you fully open the throttle it only opens about two thirds before the sliding valve hits the top of the carb. You just need to chop the valve down so that it opens fully, being careful not to trim off too much, and reassemble. Then you just need to lengthen the slot in the fascia so the lever can move further.

 

[skipper681]

Will try this myself, I have a 2.2 Mercury, I may be wrong but don't Tohatsu make that too?

 

[C08]

the Yammie 9.9HP four strokes just require a bigger jet to uprate to 15HP, the 25HP (2 stroke) Tohatsu just requires a restrictor plate to be removed to uprate tp 30HP. A well known north manchester Tohatsu dealer charged me quite a bit to uprate a new engine I bought from him and I was not happy when I found out what was actually involved. Best to always check the mixture by a plug check after these mods but I am sure peeps knowledgable enough to do this would be aware of weak mixture damage.

 

[seanfoster]

the Yammie 9.9HP four strokes just require a bigger jet to uprate to 15HP, the 25HP (2 stroke) Tohatsu just requires a restrictor plate to be removed to uprate tp 30HP. A well known north manchester Tohatsu dealer charged me quite a bit to uprate a new engine I bought from him and I was not happy when I found out what was actually involved. Best to always check the mixture by a plug check after these mods but I am sure peeps knowledgable enough to do this would be aware of weak mixture damage.

This made me prick my ears up, I have a late 80's Yamaha 9.9AE fourstroke, do you know where I can find out more about which jet size etc?

 

[C08]

This made me prick my ears up, I have a late 80's Yamaha 9.9AE fourstroke, do you know where I can find out more about which jet size etc?

It was a friends yamaha and the bigger main jet cost about £6 from Bill Higham, but any Yamaha dealer would get it for you. There was no timing adjustment to make and the engine ran perfectly and more powerfully than before but it was hard to quantify the actual power increase as he did not have a tacho fitted. Yamaha were very helpful with advice and also sent him detailed photocopied info about the uprating procedure.

 

[pcatterall]

Couldn't be easier but I know that the jet in mine is exactly the same as the 3.3 - worth checking with someone who knows. All you need to do is remove the cowel and fascia panel and look into the carb. You will see that when you fully open the throttle it only opens about two thirds before the sliding valve hits the top of the carb. You just need to chop the valve down so that it opens fully, being careful not to trim off too much, and reassemble. Then you just need to lengthen the slot in the fascia so the lever can move further.

Anything I can do with my Seagull!!

 

[Alpha22]

Anything I can do with my Seagull!!

Replace it with a 2.5 Mariner and do the mod. It worked wonders for my tender........ even the 10 year old will use it now!!!!

 

[jac]

Anything I can do with my Seagull!!

Use it as an anchor?

 

[VicS]

delted

 

[macd]

it will outlast you and all the Tomarinyamazukis

In fact it might even outlast this thread

 

[ronsurf]

Anything I can do with my Seagull!!

Tune it...

 

[blackfish]

Tune it...

Looks like it's the kind of 'tune' you get at a rave.