Upgradable small outboards.

gtflash · 10 March 2025, 17:28

Whilst shopping for potential engines for tender I have found a few that are known to be upgradable in power such as Yamaha 2 stroke 9.9 and maybe a new ish Suzuki 9.9. Does anyone have any more suggestions and years it's possible on each model ?

Fenlander · 10 March 2025, 21:10

I always urge caution with this as there are a few errors in advice all over the net regarding this across many 2/4 stroke models. The only one where I've turned the OE workshop manual inside out to prove the possibility is the Yamaha 9.9-15hp 2-stroke upgrade which is an easy no cost reset of the reed stop gap.

I also know from having them side by side the Mercury/Mariner 9.9-15hp 2-stroke upgrade involves a new larger bore carb and possibly timing/exhaust changes.... yet I've seen it stated with authority on the net in the past you just need new jets.

Another little quirk to mention. Were you considering a Tohatsu 9.8 2-stroke for its light weight beware they also made a 9.9 2-stroke which is based on the larger models and much heavier.

gtflash · 12 March 2025, 19:03

I have summarised a two stroke is a good idea, however we looked at an old 15hp mariner the other day. Weight and size all good but it was surprisingly noisy, extremely Smokey. The wife was annoyed about the noise and myself the smell and oil deposits it was leaving on the water.

I suspect it was tired but I am now not sure what I want. My BIG two stroke only smokes on first start up or when I redline it. Started considering four strokes now but not man handled one yet.

Steve509926 · 12 March 2025, 20:25

Without doubt a small 2 stroke is much noisier than a small 4 stroke, it is also smokier and smellier. However a 9.8 Tohatsu or a 15hp Yam is so much lighter than an equivalent 4 stroke. It's a compromise.
I have a 20hp Merc efi and a 9.8 Tohatsu, both brilliant small outboards in different ways and different reasons.

tinker · 12 March 2025, 20:59

Was the Mariner 15hp on eBay, in Alcester?

gtflash · 12 March 2025, 22:09

No Facebook IOW

Fenlander · 13 March 2025, 11:39

>>>looked at an old 15hp mariner the other day. Weight and size all good but it was surprisingly noisy, extremely Smokey. The wife was annoyed about the noise and myself the smell and oil deposits it was leaving on the water.

Was this run in a test bucket? There can be a huge difference in every aspect that's concerned you between a worn old engine in a test tub run at lower revs on an unknown ratio of an unknown oil type... and a newer well maintained model on the correct mix of quality oil out at sea on the back of a SIB in normal use.

We've owned many portable 2-strokes... currently a mint Tohatsu 9.8 2-stroke and mint Yamaha 15hp 2-stroke. As comparisons over the last few years we've run two modern 4-strokes... a 20hp Efi Suzuki and a 9.9hp Mariner.

Our Tohatsu runs on 50:1 Quicksilver oil mix and the Yamaha on Yamalube 80:1 mix. Mixes are made with absolute precision.

Out on the water neither smokes to a degree that makes us think wish we had a 4-stroke. Regarding noise at idle they are not much noisier that the 9.9 4-stroke but the 20hp Efi was indeed whisper quiet... startling so. Once up to speed perhaps a dB meter would show different but our perception is that while a bit noisier than the 4-strokes the sound is almost more pleasant. One thing that is noticeable both the 2-strokes are smoother than the 4-strokes... particularly the Suzuki 20hp which had a mid to upper range vibration.

Having said all that I would never try and argue against the disadvantages you experienced if you found they annoyed you even with a decent 2-stroke in normal use. After all the 2-troke popularity in portable size motors is all about weight... both our motors are 10kg lighter than their 4-stroke equivalents and that makes a massive difference to handling them at the point of setting up the outfit.

tinker · 13 March 2025, 11:56

I have never took much notice of the smoke generated from 2 strokes, I always assumed if the compression is good (pressure check them) and it runs on all cylinders (remove 1 ht cable at a time and make sure it affects the engine running) that a smokey one is down to the wrong oil mix......?

User name · 13 March 2025, 12:09

If you ran it on muffs or in a shallow bucket then the 2 stroke can be quite noisy but in real-world use I don't find them to be much noisier than a 4 stroke tbh. They can be a bit smokey if the oil/fuel ratio is too strong.

You can't beat their weight, fast throttle response and ability to punch up out of the hole though.

gtflash · 14 March 2025, 20:06

Thanks all. It was ran up in a water barrel. I've watched loads of YouTube videos of equivalent engines and the one I saw was excessively Smokey and it had oil leaking out exhaust port. Maybe wrong mix or maybe another problem. I have passed it by now.

You guys and YouTube videos have convinced me I'll look for both 2/4 stroke within my budget.

Steve509926 · 14 March 2025, 20:17

If you are thinking of anything bigger than a 15hp I would be looking at a 20hp 4 stroke EFI (still heavy but lighter than a 20hp 2 stroke)
If you are thinking of anything less than 20hp, the 2 outboards I'd be looking at are a 9.8hp Tohatsu or a 15hp Yam both 2 stroke.

chipko · 15 March 2025, 09:24

Have to agree with all comments by Mr F a few posts above.

Yes a tad rattly at tickover but sweet as a nut from mid to wot.

Hell, even our Chinese clone sounds good.

https://youtu.be/ntCck-VlV3w?si=4L1PLUYend3k2Tq-

https://youtu.be/FD0I9qNAsdo?si=tmGUaCYDfpUxcPce

Steve509926 · 16 March 2025, 11:25

gtflash,, the sib & outbound outfit mentioned by max might be of interest:-

https://www.ebay.co.uk/itm/167379412...mis&media=MORE

Looks a tidy 9.8 and if you sell the sib it's at a good price.