Mercury 50hp carburettor 4 stroke more power.

[croge321]

Hi All, I've made a bad decision and I hope that you guys may be able to help me out, I had a 60hp 2 stroke on the back of my 17' dory fishing boat, I have now changed this for a 2001 50hp 4 stroke carb version mercury. (bad decision!) I've tried various props and found her most comfortable with a 12" pitch stainless vengance, once she's on the plane she's revving to 5400rpm wot so within the specified rev range but she is very reluctant to come onto the plane, sometimes we have to shift weight around to get her up. I've read various posts about a 50 - 60hp power upgrade for the efi version by simply removing a restrictor in the air intake, is there a similar upgrade for the carb version? the only difference that i can see on the parts diagram is the isolator plate between the carbs and the inlet manifold, i thought that this must have smaller holes and act as a restrictor so i removed mine to have a look and it is the same size as the carb throats so i can't see that this is causing a restriction, the carbs are the same part number. She also seems to be running very lean at top end? she actually comes onto the plane better if i restrict the throttle a little? The carbs have been cleaned well, she idles well. she's fairly good on fuel but just needs that little extra punch. any suggestions greatly appreciated, many thanks and best regards, Chris.

 

[galamb]

First, I will get the US restrictions on what you are asking about out of the way - I'm in Canada, so doesn't apply to me.



10 extra horses won't do a whole lot for you in this case. The "umph" you need can only really be obtained by increasing the torque a fair bit which usually entails increasing your displacement.

However, in this case it "looked" fairly simple to squeeze a few horses. The only difference between the 50 and the 60 horse was the "isolator plate" behind the carbs.

BUT, the 60 horse plate is no longer available. So you may be able to find a parted out motor (recycler maybe??) - the part number you are after is 857104T (857104T1 is the plate used on the 50).

(there is a possibility this part was discontinued to prevent the very modification you are trying to do - just a guess on my part there though)