16ft skeeter with 40 mariner

[skeeter87]

Hi guys,
Im new to this boating stuff.. I love being on the water. well i got this boat and in need of a prop. I know the with just one person on the boat wide open she runs 23-24MPH but it sounds like she isnt getting the rpms that it needs. What would be the best prop for the boat.

 

[steelespike]

Re: 16ft skeeter with 40 mariner

Welcome,we need to know a lot more before we can even come close to being accurate with a prop selection. If you read"read this first at the top of the page and get uis asw much info as possible we'll get you setup.A real must is the prop size,present wot rpm and speed.
Year of boat and motor. Prop size should be near base of blades or under the prop nut.

 

[skeeter87]

Re: 16ft skeeter with 40 mariner

it has a 13 pitch on it know, And it gets me around 20-22 wot. with 2 ppl. Its a 40 horse mariner, 16ft skeeter. its all how the boat came stock nonthing was changed. its a 1987 boat and motor it is a v hall, the boat modle is a strada f80. it also dosent have power trim and tilt. dont know if that will help. But like i said it dont sound like its getting the rpms that it needs. My tach is not working right so i have no idea what they are.
THanks
Prop PArt number that i got on there now is a 48-61818A4 13p

 

[Texasmark]

Re: 16ft skeeter with 40 mariner

I had a friend with that boat and he ran a 90 hp Merc triple cylinder on it at about 45 mph. I have a '94 Mariner sales brochure and it says that the engine is 4 cyl with a 2:1 gearbox. Says the prop pitch selection for that engine is 8-19". I'd say that you need to get your tach fixed or get an elcheapo over www and find out what your revs are. Then from there considering 100 to 200 rpm per inch of pitch, move your pitch up or down (more pitch drops rpms less the opposite) to get your rpm's up to the recommended top of the operating range of 5000 - 5500 (per the manual). Then your engine will "be all that it can be".

HTH,

Mark

 

[steelespike]

Re: 16ft skeeter with 40 mariner

According to my info the F80 is a 15 footer and weighs 800lbs.
Using a prop calculator and a 2.00 gear ratio 13" prop,12% slip and 22 mph speed I get about 4000 rpm The motor is rated for 5,500. If the motor can make 5500 with a 13" pitch
the result would be about 29 mph.I believe you have a motor issue.Could be as simple as the throttle not openng all the way. Be sure the motor is in excellent tune and has good compression. To be sure you have the right setup you will need a working tach.
Induction tachs are about $50 you might use an optical tach.gps speed is the most accurate.

 

[skeeter87]

Re: 16ft skeeter with 40 mariner

The thortle is open all the way. It might be able to go a tiny bit more. the motor runs like a champ. also i do think that the carbs do need some tuning. what is the best way to tune them?

 

[steelespike]

Re: 16ft skeeter with 40 mariner

Is the motor a 2 or 4 cylinder?My info indicates a 2 cylinder.You do need that tach to confirm
your rpm If it is indeed at about 4000 rpm you can't make that up with a prop.
Check your setup below before fiddling with carbs or ignition that imeadiately follows.
About the only tuning you can do is set the idle 2 cylinders at about 850 in gear. rpm.And adjust the idle mixture screws initial setting is 1 7/8 to 2 3/8 turns out from gently bottomed.Then adjust to best idle at about 850 in gear.Otherwise its time to rebuild.
Ignition timing on 2 cylinder motors is involved but start by checking the point gap.Standard magneto points are set to .012-.016.Should be a hole in the flywheel to check points.
Lets check your setup.The antivent plate(just above the prop should be visable when on plane.You can raise the motor by just putting a stick on top of the transom to hold the height while you tighten the clamps.Just be sure the clamps have a good grip.Try various trim settings.Trim out (prop away from boat)should improve top speed but slow hole shot.Trim in improves hole shot slows top end.Try to find the ideal.
Try to balance weight neither too much stern nor bow.Many small boats end up with 2 portable tanks and a battery in the stern this slows hole shot and usually makes it difficult to stay on plane or find the ideal trim setting.
Is the prop in excellent condition?

 

[skeeter87]

Re: 16ft skeeter with 40 mariner

prop is in ok shape its got some chips and like on bend were i had to bend it back. I know thats got some thing to do with the issure i have also.