Help - Over 115 more HP but same RPM!!
05-27-2007 | 03:54 AM
#11
Charter Member # 55
Joined: Oct 2000
Posts: 20,241
Likes: 2,490
From: Omaha/LOTO
I haven't checked the plugs since the mods, but prior to the mods the plugs were very dark grey to almost black, not oily, more of a carbon build up.
The carby is a 650cfm Demon.
Thanks to everyone for all the feedback. Looks like I need to replace the exhaust manifolds. There seems to be only one option in Australia being the Hi-tek manifold. Are they popular in the States? Any other recommendations, options and suppliers in the States that can freight to me? Need throttle/gear assembly mounts on Starboard manifold and oil filter mount on port manifold.
I will also replace the baby flame arrestor with a K&N . This raises another question, due to clearance issues under the hatch, am I better off using the 59-3264 (339cfm) with 3-3/4" height and keeping my 1" spacer between the manifold & carby OR go the 59-3364 (466cfm) with 4-1/2" height and no spacer between manifold & carby. As above any recommendations on suppliers/forum sponsors that can freight to me.
The carby is a 650cfm Demon.
Thanks to everyone for all the feedback. Looks like I need to replace the exhaust manifolds. There seems to be only one option in Australia being the Hi-tek manifold. Are they popular in the States? Any other recommendations, options and suppliers in the States that can freight to me? Need throttle/gear assembly mounts on Starboard manifold and oil filter mount on port manifold.
I will also replace the baby flame arrestor with a K&N . This raises another question, due to clearance issues under the hatch, am I better off using the 59-3264 (339cfm) with 3-3/4" height and keeping my 1" spacer between the manifold & carby OR go the 59-3364 (466cfm) with 4-1/2" height and no spacer between manifold & carby. As above any recommendations on suppliers/forum sponsors that can freight to me.
The smaller K&N will be fine and supply plenty of air. The shift linkage and the remote oil filter can be mounted easily on the transom. No need to mount them on the manifolds. I've never heard of the Hi-Tek manifolds.
I think the thru prop is hurting you much more than the actual manifolds. You need to run thru hull exhaust. I think the stock manifolds will work ok. Not optimal, but you should see a decent improvement in power just going to thru hull.
Get a template for the standard exhaust hole cut outs and some SS exhaust tips with internal flappers.
05-27-2007 | 05:09 AM
#12
Platinum Member
Joined: May 2005
Posts: 228
Likes: 4
From: Sydney Australia
http://www.hitekmarine.com.au/ is the web site.
Do a search on hi-tek and you will see a few people have used them.
That will be the next upgrade on my boat.
Do a search on hi-tek and you will see a few people have used them.
That will be the next upgrade on my boat.
05-27-2007 | 03:13 PM
#15
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Joined: Aug 2005
Posts: 242
Likes: 2
From: Merritt Island, Fl
I think that it may be as simple as way too much prop. You aren't letting the engine get into its powerband. Drop some pitch and you should reap significant rewards. I am assuming that everything is set right with regards to jetting and timing.
Rene
Rene
05-27-2007 | 03:29 PM
#16
Charter Member # 55
Joined: Oct 2000
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From: Omaha/LOTO
05-28-2007 | 08:50 AM
#20
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Joined: Oct 2000
Posts: 543
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From: Sussex, WI
Exactly what everyone said about exhaust, you have to change it. Think of the motor as a big air pump,
What your doing is like sucking the air in a 10inch hole and forcing it out of a 5 inch hole, it's impossible to move the volume of air you need to.
What your doing is like sucking the air in a 10inch hole and forcing it out of a 5 inch hole, it's impossible to move the volume of air you need to.
