what would you pros suggest

[my1stboat1]

1988 bayliner/trophy Center console...
16 foot
85 hp force outboard.
current prop is 13x17
Max Rpm wot 4700
Max speed is 30 to 32 mph

what prop would you guys consider as an upgrade....

 

[walleyehed]

Re: what would you pros suggest

Not to sound harsh but "what 13X17"? what model...make???
Alum or stainless? If we know what prop then we know what would be an "upgrade".

 

[my1stboat1]

Re: what would you pros suggest

its the factory prop, Its aluminum, its 13inches in Diameter & 17 pitch I would like to go to a stainless prop

 

[walleyehed]

Re: what would you pros suggest

Looks like you'd need to drop to at least a 15P in SS. Best rpm should be a target of 5200. just dropping to 15P will not gain what you need rpm-wise, but raising the engine mounting location a hole-maybe 2 should get you around 5100+/- a few.
Check the trailing edge of your current prop and see if it's flush or cupped...the stock 13X17 was not cupped...if this is the case we'd have to drop to a 13P in SS.
The most cup would be apparent where the blade meets the hub...if you can check on that and post back, that'll tell us where to start.

 

[Bifflefan]

Re: what would you pros suggest

what prop would you guys consider as an upgrade....

Im more wondering about the motor condition. On my old Starcraft 16' with an 85 Johnny, She would go a fair piece faster (about 45 mph) with a 17p and a well tuned engine. Also I could use a 19p and still run at 5200 RPM WOT with 2 people.

Does the engine needing tuned?

 

[walleyehed]

Re: what would you pros suggest

45mph with a 17P is not possible unless you are spinning around 6250+/- a few. 5800+/- would be your rpm with the 19 if this was true speed.
I'm getting right at 42mph GPS with a stock alum OMC 13-1/4X17 @ 5900 on a 1978 85 Johnson on a supersport16.
I don't know off-hand what the gear ratio is on the Force either....that can make an inch or 2 of change in pitch as well.
The JohnRude of that era put out a good 10-15hp more than the Force as well...and, if their both 2:1 ratios 4700 (Force) and 5800 (OMC), there will be a HUGE difference.

 

[my1stboat1]

Re: what would you pros suggest

i inspected the prop. and i dont believe its cupped... Where the trailing edge of the blade meets the hub its pretty much straight not cupped ... the transom bracket on my boat says min rpm 4500 to 5800 I know im not running high in the rpm range but i can tell you that the engine is running tip top accelerates cleanly from dead stop or moving it purrs wot for me at 4700 4800 rpm Im just looking to try and pick up a few more RPM AND TOP SPEED

 

[walleyehed]

Re: what would you pros suggest

figuring your numbers, the tach seems real close but dropping to a 15P (Cupped) is the same as the 17 un-cupped. Problem is this engine, if healthy, should be getting a few more rpm. If we follow the "rule of thumb" on pitch, we;re going to be looking at a prop normally used on pontoons....something isn't adding up. Let me research something first...