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1989 58 cobra low gear ratio

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aaronb

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"hello i recently purchased a

"hello i recently purchased a 1989 four winns horizon 200 ls and the out drive model 985689 matches the numbers in the seloc book butt mine has another tag next to the model that says its a 1.50:1 high altitude gearing and the manuel says it should be 1.41:1, so with that said since my prop is spinning slower than normal can move from a 15 x 17 3 blade to say maybe a 14 x 19 or will that put to much physical torqe on the out drive. by the way my numbers are good 4500 rpm max at about 42 mph but i would love to see the mph climb a little . and one more question can you tell me what kind of elctronic conversion i can for the distributer somting so i ca run hotter coil and plugs thanks"
 
"[i]my numbers are good 4500 r

"my numbers are good 4500 rpm max at about 42 mph

That's it then, you are at your max mph.
Your engine makes it's maximum torque at 4500 rpm.
If you increase the pitch, you will lug the engine and more than likely go slower or the same speed.
If you want to go faster, you need more engine power, or less weight.
A stainless steel prop usually nets 1 to 3 mph.

There's probably a Pertronix electronic ignition conversion kit. You'll also need to swap your ESA to an electronic compatible unit from CDI/Rapair.

But that won't be a performance upgrade, just a maintenance reduction upgrade so you don't need to service the points anymore."
 
"aaron,i have a 93 351 cobra a

"aaron,i have a 93 351 cobra and i changed my prop last season to a 141/2x19 Michigan Wheel Ballistic and only lost 100 rpm runs great. Going to try a 21 pitch this season."
 
"Harry if you keep the same di

"Harry if you keep the same dia then you will lose another 300-400 RPM's, what is your WOT RPM's now?"
 
"thanks for your help guy'

"thanks for your help guy's but Hy Stat my wot is 4000 to 4500, for mileage sake how do i get it to run in the area of 4000 rpm.

and harry did you notice any changes in how the boat performed with that 14-1/2x19 or was it not noticable ie: mileage, plane, low end, high end, hole shot, or economy"
 
"[i]for mileage sake how do i

"for mileage sake how do i get it to run in the area of 4000 rpm.

back off the throttle to get to 4000 rpm.

In a boat, throttle position and fuel consumption are almost linear when on plane."
 
"hey stat how i do apreciate a

"hey stat how i do apreciate an attemp at the obvious answer, at 4000 rpm im only reaching speeds of 34 mph im not looking to loose speed just rpm"
 
"Aaron, i have not checked my

"Aaron, i have not checked my fuel economy,plane is good due to the help of a hydrofoil by Cobra The Edge that bolts underneath the cavitation plate that made a dramatic difference in planing speed and time.Hole shot is good. How old is your prop,is it stainless, is it a cupped or uncupped unit. If is a uncupped unit,a cupped prop will lower your rpm and will also help with bite and mph"
 
"harry thanks for your info ,

"harry thanks for your info , im curious though i have a 89 four winns horizon 21' with 351 cobra and i can only see 42 mph and your hitting 53 on your 1993, what kind of boat do you have."
 
"Aaron it is a Seaswirl Spyder

"Aaron it is a Seaswirl Spyder 208, 21' pleasure boat. I'm curious, what are your initial and total timing settings"
 
"[b]Bob,my wot is 4400 rpm at

"Bob,my wot is 4400 rpm at 53 mph

Harry then I guess you would be ok going to a 21 pitch, you'll just go from the top of the max RPM range down closer to the bottom. You may pick up a couple of miles per hr once you get up there but you may notice it being a little slower getting out of the hole. Like everything else in boating it's all about compromise!"
 
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