Mariner 2.5hp two stroke conversion

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alecB

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Hi all,
I've previously used the advice given to another enquirer in this forum about stripping my Mariner 2.5hp to clear the water channels, this worked a treat and restored the 2.5hp to rude health. Elsewhere, the contributors showed how to adjust the 2.5hp and make it a 3.3hp very easily, albeit with no gear changes. This I haven't done but have seen how to do it on my 2.5 and may try it this winter when the season's over.

The 2.5hp is a great reliable motor for me but there are 2 things I would change if I could ( I can't buy another engine because of financial constraints).

The first is that it has the 'kill' button, not the type to have the engine stop with a lanyard. Is it possible to convert this stop button to the better kill switch for the improved safety it would bring?

Secondly, the tiller arm on the 2.5 is for steering only and is basically a stick on a pivot bolt, the power being adjusted by the lever on the front of the engine hood. Is it possible to get a twist grip throttle arm and make it work with this model? The reason for asking is that there are plenty of twist type arms on ebay at low cost with the wires attached, but is the conversion possible at the carb end?

thanks
 
I have a Mercury 2.5hp 2 stroke, which is I think is essentially the same. It came with a killcord button - you pull the kill cord off and it stops. So I think they're interchangeable.

What I'd really like is a reverse gear. Having previously had a Mercury 3.3 I assumed it had one when I bought it!
 
I've got a mariner 2.5 and it has a kill cord, like DaveRo's mercury.

What *I'd* really like is a neutral position, though I seem to have become ok at yanking out the kill cord at an appropriate point to drift gently towards my target
 
Thanks guys for the info, DaveRo + Laika good to know the swap should work ok.

Lakesailor, thanks as well for the ebay link I'll certainly take a look at that after posting this reply (I do believe it was your post on cleaning the water channels that I used last winter, an easy job, thanks for that as well).

I wonder how much of a nightmare the twist grip change would be in your opinion....beyond basic disassembly/refit or are we talking having to fabricate parts? If the latter I get the point. Is the carb on the 2.5/3.3 not setup (for another model) to receive the cables for having a twist grip? It's highly unlikely I know but I would never have guessed the 2.5 could be made into a 3.3. I was hoping that the manufacturers were doing the same sort of thing with the other parts of the engine only ommiting to let Joe Public know so they would shell out for the upgraded models.
My interest comes from the difficulty on my dinghy of adjusting the throttle lever as there is a fair gap from the back of my seat to the outboard, so I have either to lean back and stretch or sit on the rear deck to use easily. I had a Johnson 2hp mid 90s and it had a twist grip, much easier to use and safer as the revs dropped when you let it go. The Mariner is a gem though, for me far better running, though that may just be luck with the Johnson that kept getting over rich despite paying for a strip down and tune. Thanks to this forum I now do all my own servicing.
Any input good or bad's appreciated
 
I sometimes use an alloy tube that slides over the tiller as an extension on my little Mariner. It helps me to get forward when I'm in the dinghy on my own.
I've thought of fitting a thin rod at the engine end that would reach the throttle, and possibly hook over it, to give me a crude twist grip. Not got round to doing it, but no reason it shouldn't work. Only cost a few pennies.
 
alecB said:
I wonder how much of a nightmare the twist grip change would be in your opinion....beyond basic disassembly/refit or are we talking having to fabricate parts? If the latter I get the point. Is the carb on the 2.5/3.3 not setup (for another model) to receive the cables for having a twist grip?
Click to expand...

You would need to look at the throttle slide to see if it could take a cable. The throttle slide is unique to the 2.2. I have a dim memory that it looked like it could take a cable (slot in the side and a recess to take the nipple on the end of a cable). You'd also need to check that you could fit a return spring between the cap on the carb and the slide - there may well need to be another drilling for this which may or may not be present. Then you'd need to see whether the cap on the top of the carb would take a cable - maybe a cable adjuster will screw into the existing cap?

You'd probably need to study the part numbers for the relevant motors to see what is common, otherwise you're designing something of your own from scratch.
 
Thanks guys...Rigger Mortice, I've tried that tube as well and it does work and is fine for long stretches of powered sailing when you know you don't have to adjust the throttle. I thought of something similar for the throttle but didn't think it would be easy to be precise with throttle changes at low speed with an extension piece.

Misterg, I think you are more along the lines of what I'm trying to do, thanks for the heads up from your recollections. I'd like to see a schematic of how a carb with twist grip attachment points should look to compare to mine. I can access the schematic for the 2.5 from previous postings, but it doesn't help not knowing where the (twist grip)connections should be in the first place.

Anyone idea of which low power models starts the twist grip as standard and where to get a schematic or even a photo?
 
Thanks misterg, I recognize that arrangement, I've got it on an old seagull in the garage. So, it is starting to come together ( in my head), the jpg has explained what I need to do. I'll investigate at the weekend.
 
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