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Propeller advice wanted twin 300R on 35ft deep v cc

Guest Contributor

Looking for propeller advice for my boat.

Boat details: Marlin 350 SF, 35.6 ft long, deep v 24 degree deadrise, euro transom style, engine center to center 27", engines twin 300R HD CMS, turning inwards, current tie setting 1/4 inch toe in (experimenting with toe in, parallel and toe out.

Don't know exact Hull/boat weight.

Current tested propellers:

21" Bravo1 FS, run 51.9knts at 5800/5900rpm quarter tank

20" Bravo1 FS, run 49knts at 5700/5800rpm, half to 2/3 tank level) 

Next, want to test 19" ecos

Also what I noticed, fastest speeds are achieved with minimal trim out - which makes me guessing to need more stern lift? 

Would like to try Bravo1 LT in 19 or 20 inch (but dealer doesn't have for testing), maybe lab finished even or strong advice to go 3 blade for speed? 

Cruise speed at 4200rpm around 32knts, at 4700rom around 37/38 knts. 

Like top speed and good cruise speeds. 




Guest Contributor

After reading the prop school 1-9 yesterday, will first change the setup from turning IN to turning OUT and compare the speeds without changing the props to have a 1:1 comparison which setup is faster and only then continue experimenting with other props.

Team Racing
Team Racing

Looping in Mercury Racing's Propeller Manager, @NickPetersen 

I am a Brunswick employee.

Official Racing Partner

I have done some set up on one of these hulls.. What a great riding boat. A full bottom design offers some drag so a blade that stays hooked up and that is key to a great mid range. With your numbers, I know your getting a good bit of slip from the BRAVOs. If you go ECO you will gain loads of traction and Bow lift which is what that giant needs. Also.. noted is your CMS mid sections.. That is an ultra light 300 HP motor easing the load off your transom therefore even more bow lift is needed. I would think a, ECO 19” XP (if that’s available) would be the ticket. Maybe also note here.. Is the bottom painted?? If so, we may need to adjust some numbers to match the added drag. 

Team Racing

Hi Rouven, awesome setup. If you're running about 58 mph at 5800 rpm, those are very low slip numbers for Bravos. Consider keeping the 21 FS's and raising the engines up one hole on the transom. 

Guest Contributor

Thanks @NickPetersen @ and@DrCatcher. I was some time away due to a loss in the family.

I appreciate your feedback and will try both advises. Meanwhile I had changed the lower units, which are now "turning out". The boat ran like a 1knt higher too speed the other day (50knts with the 20" B1 FS)

But I feel like the stern of the boat is lower in the water while running?!

I had chosen in particular the HD CMS version due to the lower weight, bottom is NOT painted.

This is how she sits in the water with a half tank of fuel. 


Guest Contributor

One more thing, I wrote about the minimal trim out only before loosing speed, I will remove the trim limit pins (currently positioned in the lowest holes).

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