Prop suggestions for 90 hp Force [Archive] - AZBZ Forums

: Prop suggestions for 90 hp Force


EdgeXXL
April 26th, 2009, 12:10 AM
I have a 1997 Quantum bass boat with a 90 hp Force outboard and need some prop suggestions. I had the boat out at Rosey today for the first time for a shake down test and noticed some interesting stuff.

First off I bought this boat from someone who lived in Flagstaff. They only used it maybe 5 times on some of the smaller lakes up in that area. I have the factory service manual for the engine and it states that at higher elevation to use a smaller pitch prop because of Peak RPM drop.

The manual states that at WOT the engine should be running 4750-5250 PRM. Today at the lake at WOT the engine was running at 5600 RPM when trimmed to run at the highest MPH on the speedo. The boat would do around 37-39 MPH max. I didn't get to run it as much as I wanted to because of strong winds and of course fishing time but we rung it out good just to see what it would do and to test some stuff. The boat was loaded with what I would consider a standard load. Two people and gear. The motor ran great and the boat handled good. I am worried about running the RPM that high and was wondering if a prop with more pitch would be the ticket to get the RPM down and maybe some more speed. The prop on it seems to be the original with a part number
48-77344A40 17P. It was suggested by one of the local boat dealers to use a 13 X 19 prop. I don't want to waste money and get the wrong prop so thought I would ask for some guideance and suggestions.

Thanks Rick

HawkCoach
April 26th, 2009, 12:55 AM
I believe the higher number pitch you get less rpm,s, so you would want to go to a 19p-21p prop. Anyone correct me if I m wrong, Hope that helps.

Joey
April 26th, 2009, 04:30 AM
I believe the higher number pitch you get less rpm,s, so you would want to go to a 19p-21p prop. Anyone correct me if I m wrong, Hope that helps.

Sounds about right, but im not sure....

Trroscoe I saw you guys out there today!!!

Fish Hawk
April 26th, 2009, 07:22 AM
I have a 90hp motor on my boat and I don't think you going to get much more out of a 90hp motor. I run the same speeds and rmp's that you are. If you find a combo that gets you 5mph more please post.

DanW
April 26th, 2009, 08:40 AM
A 19 should put you at the proper rpm's, and maybe give you a few more mph. You will lose some holeshot though.

bass_trackin
April 26th, 2009, 09:15 AM
I run a 19p stainless on my 90 opti and it's the perfect pitch for the motor. I've ran a 15p and a 17p and both of them are two small for the motor even in Utah were the elev is a couple thousand ft higher. If you go to props plus they will let you try a couple different props to see which one you like best. :)

EdgeXXL
April 26th, 2009, 10:09 AM
Joey where abouts did you see us. My boat is pretty hard to miss. White and maroon with Quantum across both sides. Probably dont see a lot of them out on the water. What boat were you fishing from. There were lots of people fishing because of the tourny that was going on. We only cought a couple slots but this trip was really about just shaking the boat down and to do a little fishing. I was dreading going by myself as I could find no one that I knew who wanted to go. My 22 year old son finally relented and went with me. Thankfully he did go as it was nice having someone to help me launch and reload. We had fun despite the wind but decided to leave early and go eat some mexican food at Guayos on the way home. My parents live in Miami so it was a nice visit on the way back to Tucson. So far I am pleased with the boat and think I will be keeping this one for a while. Only thing I wish it has is a rod locker. Everything else is great. The boat is a 97 that was only used a few times by the previous owner and is practicly new. Heck its the nicest boat I have ever owned and I got it for a steal. I am getting ready to retire from 29 years in the Air Force and will have plenty of time to use it. I will move up to a serious tourny style boat in the future but this one is good for now.

The only reason for the prop change is to get the RPM down to the recommended range in the factory service manual. If I can pick up a few MPH that would be nice too but not really necessary as I am ok with the speed it has.

Rick

Bob La Londe
April 26th, 2009, 12:14 PM
Gary Knight, The former owner of Davidson Marine once told me about 1" in pitch equals 100 RPM apx.

I found his estimate for my boats to be close. It will vary some depending on the boat.

Also, the rpm you experienced could be due to engine height, trim, quality of the prop, etc.

Some boats like flat bottom jon boats can't be trimmed past level anyway.

Motor to high may cavitate a little.

Damaged prop may cavitate a little.

I would have a hard time making a judgement on what you need to do based on your post, but I would certainly find out if you can borrow a taller pitch prop and see what happens to your performance.

Also, use a GPS to gage speed and always make back to back runs in opposite directions.

Dialing in a boat is a process that deserves to be focused on. I may see what a boat is doing when I take it fishing, but when I decided to focus on dialing it in I make a special trip to the lake just for that purpose, with my tools ready, and if possible a friend handy so we can trailer, adjust and re-launch quickly.



I have a 1997 Quantum bass boat with a 90 hp Force outboard and need some prop suggestions. I had the boat out at Rosey today for the first time for a shake down test and noticed some interesting stuff.

First off I bought this boat from someone who lived in Flagstaff. They only used it maybe 5 times on some of the smaller lakes up in that area. I have the factory service manual for the engine and it states that at higher elevation to use a smaller pitch prop because of Peak RPM drop.

The manual states that at WOT the engine should be running 4750-5250 PRM. Today at the lake at WOT the engine was running at 5600 RPM when trimmed to run at the highest MPH on the speedo. The boat would do around 37-39 MPH max. I didn't get to run it as much as I wanted to because of strong winds and of course fishing time but we rung it out good just to see what it would do and to test some stuff. The boat was loaded with what I would consider a standard load. Two people and gear. The motor ran great and the boat handled good. I am worried about running the RPM that high and was wondering if a prop with more pitch would be the ticket to get the RPM down and maybe some more speed. The prop on it seems to be the original with a part number
48-77344A40 17P. It was suggested by one of the local boat dealers to use a 13 X 19 prop. I don't want to waste money and get the wrong prop so thought I would ask for some guideance and suggestions.

Thanks Rick