How fast should I be going?
#11
I have a Sutphen 30. Your boat weighs 5800 lbs.
I am running a totally different set up, so I can`t really offer you any comparison.
I have stock Merc 420`s / TRS / 26P Bravo 4-blades. My props are too big for these engines. I can only get 4100 rpm and then it quits pulling. I`m seeing 64 on GPS speedo.
I`d love to try smaller props to get my R`s up. I`d like to see upper 60`s at least.
Good luck
I am running a totally different set up, so I can`t really offer you any comparison.
I have stock Merc 420`s / TRS / 26P Bravo 4-blades. My props are too big for these engines. I can only get 4100 rpm and then it quits pulling. I`m seeing 64 on GPS speedo.
I`d love to try smaller props to get my R`s up. I`d like to see upper 60`s at least.
Good luck
#12
Registered

Joined: Nov 2004
Posts: 14,100
Likes: 3,687
From: On A Dirt Floor
I just reread combo and the 34 dgrees total timing just jumped out.
Do you have factory OE heads ?
If so, the total timing on a performance build usually ends up being 36-38 (some even more
) because of the combustion chamber design.
Bump up timing two degrees, do a run, note performance, and check plugs for any signs of detonation. I'd probably run 91-92 octane fuel just to be safe.
If performance does jump, try another degree or two and recheck plugs.
Some motors don't respond much to few degrees of timing, but some really wake up. Only one way to find out.
Do you have factory OE heads ?
If so, the total timing on a performance build usually ends up being 36-38 (some even more
) because of the combustion chamber design.Bump up timing two degrees, do a run, note performance, and check plugs for any signs of detonation. I'd probably run 91-92 octane fuel just to be safe.
If performance does jump, try another degree or two and recheck plugs.
Some motors don't respond much to few degrees of timing, but some really wake up. Only one way to find out.
#13
I will ttry this for testing purposes. I would be scared to keep it that high. The plug readings showed the timing to be a little high at 35 so I backed it off to 34 and the now the readings are almost perfect.
I saw no performance difference between 34 or 35.
I used to run 87 octane I went up to 89 to be on th esafer side. I will try some 91 or 92 when I up the timing.
I saw no performance difference between 34 or 35.
I used to run 87 octane I went up to 89 to be on th esafer side. I will try some 91 or 92 when I up the timing.
Originally Posted by SB
I just reread combo and the 34 dgrees total timing just jumped out.
Do you have factory OE heads ?
If so, the total timing on a performance build usually ends up being 36-38 (some even more
) because of the combustion chamber design.
Bump up timing two degrees, do a run, note performance, and check plugs for any signs of detonation. I'd probably run 91-92 octane fuel just to be safe.
If performance does jump, try another degree or two and recheck plugs.
Some motors don't respond much to few degrees of timing, but some really wake up. Only one way to find out.
Do you have factory OE heads ?
If so, the total timing on a performance build usually ends up being 36-38 (some even more
) because of the combustion chamber design.Bump up timing two degrees, do a run, note performance, and check plugs for any signs of detonation. I'd probably run 91-92 octane fuel just to be safe.
If performance does jump, try another degree or two and recheck plugs.
Some motors don't respond much to few degrees of timing, but some really wake up. Only one way to find out.
#14
Originally Posted by HigherPower
I have a Sutphen 30. Your boat weighs 5800 lbs.
I am running a totally different set up, so I can`t really offer you any comparison.
I have stock Merc 420`s / TRS / 26P Bravo 4-blades. My props are too big for these engines. I can only get 4100 rpm and then it quits pulling. I`m seeing 64 on GPS speedo.
I`d love to try smaller props to get my R`s up. I`d like to see upper 60`s at least.
Good luck
I am running a totally different set up, so I can`t really offer you any comparison.
I have stock Merc 420`s / TRS / 26P Bravo 4-blades. My props are too big for these engines. I can only get 4100 rpm and then it quits pulling. I`m seeing 64 on GPS speedo.
I`d love to try smaller props to get my R`s up. I`d like to see upper 60`s at least.
Good luck
I have a set of 22 bravos that would probably be perfect for you. Too bad your in Texas. I wouldn't mind trying the 26's.
#16
Originally Posted by PatriYacht
Plugs look good. I wouldn't lean it out any. Sorry, just wanted to check.
Thanks Rob
#18
The only things that look out of place on your build are the Air Gap intakes. There are a couple of used HP500, Dart intakes for sale in the classifieds. That's what I'd use.
#19
I used to have a 30' Scarab with 420's and TRS drives. It weighed 6800 dry according to the factory. It went 70 with 23 pitch 3 blade cleavers. This size boat always seemed to run well with 3 blade props. With almost 100 hp more a side you should be able to spin 25 pitch Mirages.
#20
Registered

Joined: Aug 2001
Posts: 919
Likes: 13
From: OPKS & LOTO
Originally Posted by Leathl_WS6
I never actually thought about it that way. Could be but with the exhaust change this year I pick up 500 rpm in midrange but noting in top end. Similar setups are making over 500hp at 5k. Not saying that means mine are for sure but if they aren't I think they should be.
I have had a smaller set of props on one time they were 22 bravos. The lake was too bad that day I could not get a WOT run but the motors did spin up past 5400 speed was under 70. I am working on getting some different props to try.
Thanks Rob
I have had a smaller set of props on one time they were 22 bravos. The lake was too bad that day I could not get a WOT run but the motors did spin up past 5400 speed was under 70. I am working on getting some different props to try.
Thanks Rob
Any interest in trying a set of 23P Mirage's? It's what I'm running now and would love to swap and try your 22P Bravo's.


