engine advice, merc 7.5

ollyit · 24 May 2006, 10:30

Took my newly aquired merc on its first trip out on my tender,2.6 metres last night in the local creek, only had it run in the tank before hand, well my mums recycle bin, (shhhh she's on holiday!!)

rubbish all over the lawn

starts and runs well, although I'm not convinced under thrust and in forward gear its achieving full power, my mates 4hp merc got it up on the plane and this wont and its 3hp more! , I've tried different trim angles etc, theres a lot of resistance on the throttle on the tiller were it wont stay or go to "fast" mode (twist grip to the right), on closer inspection under the hood, theres a pulley wheel which the cable wraps around that wont fully turn as one part of the cable appears to be rusty and warped, is this an easy job to do? - I'm reluctant to take it somewere, how do i source one? pictured below is an image i took off the web, but I've highlighted the area of concern - thanks for any pointers

ollyit · 24 May 2006, 15:10

had a nose on the http://www.outboardrepairs.com/rpm/ website,
shall I try different plugs? - Im sure its running fine on both cyclinders, very balanced so to speak hmmm... the plot thickens

Nos4r2 · 24 May 2006, 22:25

Open the throttle full and look directly into the mouth of the carb.

If the butterfly valve that opens and closes when you open the throttle isn't horizontal with the throttle wide open then the throttle isn't opening properly.

Downhilldai · 24 May 2006, 22:25

If it's running nicely on idle and low RPM, but you suspect you're not getting full throttle due to rusty linkages, etc., I'd try sorting that out before looking into the spark plugs. If you're not getting full throttle, you're not getting 7.5hp.

Nos4r2 · 24 May 2006, 22:27

Yep.

Make sure you've got the right plugs in there though. You'll notice a power loss if they are the wrong ones.

BTW, try Iboats.com forums and post it in the merc troubles section. You'll find someone there who has worked on the same engine previously. Give your serial number and HP and they'll tell you the right plugs too.

ollyit · 25 May 2006, 09:05

sounds like good advice boys, thanks