Figure out what prop size?

[Tiger123245]

I just bought a used 23' pontoon with a 1990 90 HP Force outboard. It needs a new prop (the current one is usable but needs to be sent in to be repaired due to fracture on one of the "fins", plus I'd like to have a spare, just in case) and the skeg has been broken off.<br /><br />The current prop has no markings on it other than "15C", no model, serial numbers, etc. How do I figure out the pitch and diameter to get a new/remanufactured/used prop? FYI: This boat only has a speedometer, no tach so I can't judge the RPMs. Full tilt on the lake this weekend I got about 15 MPH, but that was with some pretty choppy waves going on.<br /><br />I've read online that the skeg can be repaired by welding a new piece to it. Anyone have that done? How much approx. can I look forward to spending to have that done? OR.... I looked at this website for a Skeggard (sp?), if your skeg is pretty much gone can you still put one of these on?<br /><br />I live in a smaller size city in SE Iowa and the only local RV & Marine shop is known to really gauge people on parts, so any info on so I can try online to find this stuff out would be helpful. <br /><br />I'm new to boating and a chick so although I'm pretty handy with tools and minor electrical work I'm sure I'm going to be asking a lot of questions on this site! I've already gained a lot of info from reading other people's questions. By the way, what does "WOT" mean?<br /><br />Thanks!

 

[Dunaruna]

Re: Figure out what prop size?

Where to start?<br /><br />WOT - Wide Open Throttle. AKA flat out, pedal to the metal, ludicrous speed .<br /><br />It would be a fair asumption that you are not going to get that puppy planing, so speed isn't an issue. Let's concentrate on longevity.<br /><br />Visit a prop shop or online (iboats megamall have a prop finder), see what suits your force. You will probably need to use trial and error until you have the best prop. To this end, a tach is a must. Your motor has a maximum reccomended RPM. Ideally, the prop should allow for WOT RPMs' so that the motor doesn't 'lug' (prop pitch too high) or 'over rev' (prop pitch too low).<br /><br />In the FAQ section of these forums is a very good article on prop selection - read and learn.<br /><br />Good luck.<br /><br />Aldo

 

[roscoe]

Re: Figure out what prop size?

Yes skegs can be welded back on.<br />But.. If the welder doesn't do it right, he can damage the lower unit seals. I would look at the skegguard type products if you think you need it fixed.<br /><br />A cheap digital easy to install tach, like the ones from tinytach.com will work for you.<br /><br />You are going to have a hard time finding a prop with a lower pitch than a 15. I'm assuming that the 15 on your prop is referring to a 15 pitch. I would buy this one to start with, it should be pretty close.<br /><br />Prop: <br /> www.boat-props.com/propellers/s/pitch-15.00/prop_chart_relation_id-369/search-Product/manufacturer-Force/rotation-Standard/horsepower-90/year-1990/chart-32/index.html<br /><br />Most all parts you may need for that motor can be found in the iboats mall, mercruiserparts.com, directly from Mercury dealer, or mercurypartsexpress.com

 

[Realgun]

Re: Figure out what prop size?

Roscoe there are props out there that will work and you can get any pitch you need. Do a search on my name and Hustler.<br /><br />Basically that motor is rated to 4500-5500 prm or if I am wrong its 4800-5200rpm.<br /><br />What you want is a prop that when you push the throttle as far forward as you can go the motor will be between these numbers. Higher the better though.<br /><br />Heres another issue also say you and the guy in your life are on the boat the prop turns 5200 rpm. That god but what if the Families go along your only going to turn 4000 rpm. Thats bad. You will need to get a lower pitch prop to compensate for this.<br /><br />The reason you want the right prop is to increase the longevity of the motor.

 

[roscoe]

Re: Figure out what prop size?

Sorry REALGUN, CAN'T RECOMMEND THE HUSTLER, AS THEY ABANDONED ME WITH MY FIRST GENERATION HUBS, and now no housings to match.. oops, I hate that caps lock button.<br /><br />She can probably get a Honda or omc prop to fit too, with the right washers, if needed.

 

[Tiger123245]

Re: Figure out what prop size?

OK... according the manual (I found it in a compartment) the Rec. Oper. Range on 90 HP is 5000-5500 RPM. But without a tach, I don't know WHAT I'm running. So basically I just want a prop that is equal to what is on the boat now (since I'm assuming that's what is good for it) and I need to get the one on it repaired (one fin fractured & kinda bent a bit) while it (hopefully) still can be.<br />I'm assuming the dimeter is measured from fin to fin straight across, right? In that case it would be 13.5".<br />What about ComProp? Are they any good? I havent' seen much about them on this forum, what is the difference between 4-fin composite and 3-fin aluminum props?

 

[Tiger123245]

Re: Figure out what prop size?

Also... since I will be replacing this prop myself... The less I have to deal with regarding washers/other gadgets/etc. to make it fit, the better off I, and my boat, will be

 

[timmathis]

Re: Figure out what prop size?

After you find the size you want you can find deals on used ones at ebay.