Prop for Force 90HP with type A lower unit

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ivan555

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So here is the story: I have a 1992 Force 90HP, and a couple of weeks ago the original lower unit (type C) has failed. Hence I purchased a used unit on the e-bay. This unit(Type A) is older then the original one, and was made in late 80's. The mounting pattern was identical, so there was no problem to bolt it on. However the prop from 1992 unit (48-77344-17) does not fit the damn 1988 unit (does not slide all the way). Did anybody have a similar problem? What props will fit this unit (only Force props or Mercs as well)? Also, where should I look for them? I found some part numbers on the net: 071036 and 72128, but not sure if they will fit. Your help is greatly appreciated!!!
 
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ivan555

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Re: Prop for Force 90HP with type A lower unit

guys...throw me a freaking bone here...
 
roscoe

roscoe

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Re: Prop for Force 90HP with type A lower unit

The 1990 thru 1994 90hp used a lower unit with dual exhaust. It came out from the exhaust snout above the prop, and it came out thru the prop hub. A few 1988-89 models also used this system<br /><br />The older lower units ( most 85-125 hp 1984-1989),<br />had a single exhaust, which exited from the exhaust snout only. The prop is solid (no exhaust passage).<br /><br />Examine the lower unit to see if it has an exhaust passage around the prop shaft. If it has no passage, then you will need an old Chrysler/Force prop.<br /><br />Iboats mall sells them here. <br /> http://www.boat-props.com/propellers/
 
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ivan555

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Re: Prop for Force 90HP with type A lower unit

…forgot to ask…what is “L-Drive”?
 
chuckz

chuckz

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Re: Prop for Force 90HP with type A lower unit

That is the same LU as my 1987, 85HP. The original prop was solid. I bought a SS prop from e-bay. It is not solid but the prop washer fits perfectly in the open end. <br /><br />Buy a Force prop. This LU is pre-mercury Force.
 
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ivan555

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Re: Prop for Force 90HP with type A lower unit

Chuck, so non-solid SS prop woks alright? Can you tell me the part number please. Why do you recommend to buy a Force prop, if SS prop fits well? By the way, do you have a part number for Force prop?<br />Thanks
 
chuckz

chuckz

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Re: Prop for Force 90HP with type A lower unit

The prop was from a manufacturer that went out of business. If you look on e-bay and search "force" under boat parts, the props will show up. You'll see the same vendor with several different pitch props.<br /><br />When I said a Force prop, I didn't mean manufactured by Force, I meant designed to fit a Force engine. I beleive the OEM props were made by Michigan Wheel.<br /><br />I can't tell you what the best prop is for your boat/engine combination.
 
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ivan555

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Re: Prop for Force 90HP with type A lower unit

Chack, thanks a lot for your help, I really apreciate it!! <br />Is this prop - the one you are talking about: <br /> http://cgi.ebay.com/ebaymotors/ws/e...=4555670607&rd=1&sspagename=STRK:MEWA:IT&rd=1 <br />"RAMPAGE made by Sierra, a three blade right hand propeller made of stainless steel and fits Force V-4 motors that have shafts with 15 splines. It is 13.25" with a 20 pitch. Sierra part# 117-401320"<br />I have one more question: this prop has 20' pitch, however the original prop had a 17' pitch. Will it make a huge difference?<br />Once again thanks, Ivan
 
roscoe

roscoe

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Re: Prop for Force 90HP with type A lower unit

Yes that lower unit will require qa Force prop, without thru hub exhaust.<br /><br />I would pass on that stainless ebay prop. <br />Yes a 20" pitch prop will make a huge difference. <br />If your motor was propped correctly with a 17 pitch, a 20 pitch will not be good.<br />Also, it says it is for a Force V-4 engine, but Force never made a v-4 engine, so who knows if you can believe any of the info in the listing.<br /><br /><br />Following the iboats propfinder link above, you will come to these props for your motor:<br /><br /> http://www.boat-props.com/propeller...n-Standard/horsepower-85/year-1988/index.html
 
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ivan555

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Re: Prop for Force 90HP with type A lower unit

Thanks roscoe. Is there a way to find a part number on this prop? So I can try to find a used one (I am short of budget now)). Also, what about a 13' diameter & 16' pitch props - are they any good? I own a 18.5 ft cobra bass boat (quite light). Thanks a bunch.
 
roscoe

roscoe

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Re: Prop for Force 90HP with type A lower unit

Do you have a tach on your boat?<br />If so, do you know what your maximun rpm were when you were running at wide open throttle?<br />How was you holeshot?<br /><br />Here's why I ask, by changing the pitch of the prop, you change the amount of pressure or resistance on the motor. Less pitch = less resistance, and the motor will have a better holeshot and will turn higher maximun rpm. But you want to choose the prop that will put the rpm in the recommended range. which is 5000-5500 for your motor.<br /><br />General rule of thumb is, lower the pitch by 1 and you will increase the max rpm by 200.<br /><br />So if you know what the max rpm were before, you can choose the best pitch for the engine and performance.<br /><br />Yes that 13x16 will fit, but is priced a bit high for a used prop, seller has no previous sales or feedback. And seller says shipping to US only, her shipping charges are high also.<br /><br />On a previous post, you asked about an L-drive. You don't have one.<br />It is a 2 stroke outboard powerhead mounted vertically inside the boat, connected to a drive unit. Kindof like an i/o, but there were not a good design.
 
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ivan555

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Re: Prop for Force 90HP with type A lower unit

Roscoe...thanks a lot for helping me...I just got the original solid prop from a prop-repair guy for $50. The prop is in excellent condition and, as far as I understand, has never been remade (no numbers on the side of the hub). The funny thing is - the prop shaft nut for this older 87 unit is also different (smaller) then the nut for 92 unit. My guess is 5/8-18? Am I right?<br />Also, I have compared the my old (mercury) prop, and the only difference is the diameter of the rim (on the front side of the prop hub) is ~1mm bigger. That’s why it does not fit and slide all the way in. I will try to reduce it on the lathe next week. Thanks again for you help!!
 
chuckz

chuckz

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Re: Prop for Force 90HP with type A lower unit

That was the same SS prop I bought except an 18 pitch. It fits fine.
 
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