yamaha f-115 overproped

[pine island fred]

Have enough hrs. on the engine so that i can go wot. Max rpm is 4300, owners manual(still waiting for the factory manual) 5 to 6 k. Current prop is a s/s 13 diam, 19 pitch. Any recomendations on prop to put the rpm to 5500? . 18 ft. ctr consol, 34 gal fuel. battery, beer and wife. Dont carry any extra weight. thanks fred

 

[rodbolt]

Re: yamaha f-115 overproped

ya need to ramp that beast up so it can turn 5900 or so. that means you need about 1600 RPM. thata a lot of pitch. normally you will see about 200 RPM for each inch. so you ned to remove almost 8" of pitch. what kind of hull is it ?<br /> my reccomendation is a spin up on a dyno or with test wheel YB1624. with YB1624 it should turn 5600-5800. if it wont make power it may have a problem.

 

[Triton II]

Re: yamaha f-115 overproped

PIF, rodbolt's right in his pitch equations and in his notion that there may be a problem with your F-115. Even though you don't tell us the type of boat or its weight, a F-115 driving an average weight 18ft CC with beer, wife and 34 gallons should be able to go to 5900rpm at WOT with a 17inch pitch prop, so you may have a problem with the engine not making it rated power. Another suggestion could be that you have a prop that's been "cupped" for more pitch but as it would appear you have a new motor (and prop?) because you state "Have enough hours on the engine..." this is not the most likely scenario.

 

[bossee]

Re: yamaha f-115 overproped

Hi,<br />With 13 x 19 Yamaha black steel prop my F115 (2003) rev about 5600 at WOT (Wide open throttle).<br /> Link <br />I think it is some problem with your F115.

 

[pine island fred]

Re: yamaha f-115 overproped

Boat is an 18 ft. ctr consol, nothing special, very similar to the WHALERS. Not much depth. Tough to get speks. on the hull as it is built by a husband/wife team in riviera beach fl. and not that many around. guess i could try to call him.<br /> Dealer hung the motor out of the box and Delhay in whats left of port charlotte set me up with the prop at a very reasonable price. Had to start somewhere. Could have been worked on but I cant tell. One thing is I had to do some filing on the trim tab as 2 of the 3 blades struck the the vane when rotated. Last thing i want to do is go back to the dealer and put the boat and my wallet in there hands. <br /> Bo, thanks for the link! Do you think dropping to a 17 in. pitch will make a difference? Speed is not really important just afraid i am running to high a manifold pressure even at part power. Got to get this right as it is the last new motor we can afford to buy. <br /> OH,one more thing. Boat has quite a list to port at any speed on plain. No extra weight, fuel tank on the center line, battery aft starboard. Thanks fred

 

[ivar]

Re: yamaha f-115 overproped

Prop hitting the trim tab? Sounds like they could have put on a very aggressive prop with a high rake. <br />Can you post pics of your prop and hull? <br />What speeds are you getting BTW? <br /><br />I have a F115 on a boat similar to Bo, 19ft cabin, and getting 5800 with a yamaha alum. 13x19 prop, speed around 38-40mph on GPS

 

[mjbrueck]

Re: yamaha f-115 overproped

If you truly feel your engine is running right, I'd check the hull. The back half of your boat should be flat. Get an 8' piece of wood (make sure that it has a perfectly flat side), and move it along the back half of the hull parallel to the centerline. There should be no dips (rocker) or cavities (hook) between the hull and the wood. Having some hook or rocker may allow the boat to plane "ugly" but not get up to the speed that it should.<br /><br />With the props, the 200 rpm/1" should only be applied in small steps. At 4300 rpms, your engine is only making a fraction of the power that it will make at 5500 or 6000 rpms. If you're way off the recommended rpms, figure the additional engine power will help decrease the amount of pitch you need to lose. Also going from a 19" pitch to 11" would decrease your pitch by 60%. That means at the same efficiency you would be turning 7200 rpms at the same speed as the 19 at 4300 rpms. (An 11" pitch prop should be less efficient than the 19", further decreasing your speed).

 

[JB]

Re: yamaha f-115 overproped

Prop topic.

 

[stevens]

Re: yamaha f-115 overproped

Your RPM is so far off the target that I would suspect either your tachometer is wrong, or there is something else hindering your engine from revving up.<br /><br />Also, the list to port could be the result of propeller torque, which is usually counteracted by that little trim tab above the prop. That your boat leans could then also indicate that the current prop is an aggressive one. If you are running with the bow low, that would only add to the leaning issue.<br /><br />Maybe you could check the tach first, before you do some further troubleshooting. For example: Throttle cable properly installed? Firing on all cylinders? Fuel feed OK? Bottom not all covered with barnacles and stuff? No trim tabs pointing straight down acting as brakes? Properly installed engine height? Proper use of engine trim? No anchor hanging off the back?

 

[pine island fred]

Re: yamaha f-115 overproped

Thanks for all of the response guys! Thought something might be strange when the blades scraped the tab. Prop also has a hole drilled at the base of each blade. Wish i could post a picture, dont know how, maby the wife can do it. <br /> Boats is brand new on a lift some miles away while i assist a friend with an i/o on my lift. Will definately check for hull warpage. Tach is one of those new digital readouts ( yamaha). Fuel feed is certainly something to look into as the last motor i got from the people had a kinked line under the cowl that gave me a fit for a time. Just dont want to bring the engine back to the dealer( maby some can understand ). Will also start tinkering with that tab to see if affects the list. Dont have trim tabs and dont really want them. regards fred

 

[stevens]

Re: yamaha f-115 overproped

That little hole at the root of the blade probably looks like this?<br /><br />

<br /><br />That's a vent hole. You can find more info about it here:<br /><br /> http://marinemechanic.com/site/mercury-prop-venting.htm <br /><br />At least on Mercury engines, that standard trim tab above the propeller can be replaced by a high-rake version or a flat one.<br /><br />

 

[ivar]

Re: yamaha f-115 overproped

With the 13x19 aluminum on my F115, there's almost 2 inches clearance between prop and trim tab. <br />Your prop sounds like it could be a Yamaha pro series SS, an agressive (and expensive) prop Yamaha pro series