Any more power from this Mariner?

[Lee1]

Once again tapping the vast knowledge on RIb.net

I picked up a 2007 Mariner 4hp four stroke model: MA4M-4ST today for a back up engine and I'm wondering if it can be tuned up to get more power, I guess it's a restricted outboard with a 5 or 6hp block?
The carb butterfly is already opening full on WOT but the carb inlet is very small looks the same as the 2.5hp ones! The engine is running like a pig coughing and spluttering so I'm taking off the carb for a jet inspection and clean anyway. . . . .
Would larger jetting get any more power or is this model heavily restricted on the cam, exhaust, inlet ports etc, etc

Thanks

[Roflhat]

Have a look at the engine manuals for the 4/5/6hp if they are the same block. You can work out which parts are different using the part numbers

[Nos4r2]

Originally Posted by Lee1

Once again tapping the vast knowledge on RIb.net

I picked up a 2007 Mariner 4hp four stroke model: MA4M-4ST today for a back up engine and I'm wondering if it can be tuned up to get more power, I guess it's a restricted outboard with a 5 or 6hp block?
The carb butterfly is already opening full on WOT but the carb inlet is very small looks the same as the 2.5hp ones! The engine is running like a pig coughing and spluttering so I'm taking off the carb for a jet inspection and clean anyway. . . . .
Would larger jetting get any more power or is this model heavily restricted on the cam, exhaust, inlet ports etc, etc

Thanks

Larger jetting will just make it run too rich. You've got to have the right amount of air to go with the extra fuel

It's probably doable, but it'd be cheaper to buy another engine unless you can find a buggered 6hp.

[Lee1]

Solved after lots of research and speaking to a U.K parts supplier, it was a full carb swap the 4hp is jetted to the maximum and jetting bigger would only flood the engine, the difference between the 4hp and 6hp air intakes was almost 50%
A full carb swap was all that was needed I could also go to sail version prop for more top end speed but I would lose the exceleration the standard 4-6hp one gives. (The 4 and 6hp versions of these engines have the same standard prop)

Brand new original 6hp carburettor was £160 the unneeded 4hp carb will get some money back and help out someone out there looking for a replacement 4hp carburettor

I still can not post pictures from my I pad on here so here's a link to some pics of the two carbs on a thread I posted on the bushcraft forum, I apologise now if linking to the bushcraft forum is against forum rules.

LINK:

https://www.thebushcraftforum.uk/thr...-project.6382/

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