Right prop

[utfyrfytr]

I am running a 17' 1968 aluminum Crestliner deep V that I have been working on for a couple of years and have it where I can get it out and do some fishing. The motor is an 89 2 stroke 100 hp Mariner with a 13.25 X 17 prop (3 blade aluminum). It will currently run out at 30-32 mph at 4600 rpm. Question is do I need to try and come closer to the max recommended rpm at WOT? I would like to gain a little speed if possible. If a change needs to be made what are some suggestions? I'm pretty new to boating and appreciate all of the help.

 

[roscoe]

Maybe try a 15P, will bring the rpm up a little, take some of the pressure off the engine, and maybe get you an extra 2-3 mph.

I know it seems like you should get a lot more speed out of that boat, but probably won't get over 35 unless you really up the hp, or lose 500# of weight.

Good luck, ;et us know what you do, and how it works out.

 

[utfyrfytr]

Roscoe, Thanks for the reply. I happen to have a 13.25 X 15 prop that I was thinking about trying. I'll give it a try next week when I get out again and then get back with you and let you know what happens. Thanks again

 

[HeavensFence87]

I had the opposite issue where my rpms were too high so I propped up so ide have more bite l. Switched from a 15p to a 19p my rpms returned to an acceptable range with no noticable change to mph maybe 1-2 mph max. Propping down will give you better hole shot and allow you to plane faster but I highly doubt it will increase your top end. Regardless I think the change is worth it.

 

[Sea Rider]

Propping an engine right to rev higher towards full wot rpm range factory stated usually reduces top end speed. A matter to check which modality suits your boating needs best : Top hole shot or slight more top end speed, but can't have both worlds in just one prop, as one modality opposes the other.

Happy Boating

 

[WesNewell]

Also, having the engine mounted at the proper height can increase speed up to 10-20% I gained 10% from 35 mph to 38.5 mph just by mounting my engine 1.5" higher and increased fuel economy. Any part of the shaft above the av plate that's under the water line produces a lot of drag, reducing speed and fuel economy. From factory every aluminum bass boat I've looked at has the engine mounted too low. I'd suspect the deep V are the same, maybe more so. Trim your engine with av plate in line with hull bottom. Go wot. The av plate should should be just above the water line for max performance.