How fast should a 115 go?

[GA Paramedic]

I have a 1976 18' ski boat with a 115 inline 6 merc with a 19 pitch stainless steel prop. I cleaned my carbs & fuel pump and replaced my timing belt. With a little help, I finally got it to plane out yesterday on the lake. What should my exstimated speed be on the lake at WOT? Thanks in advance for your help.

 

[ricksrster]

Re: How fast should a 115 go?

What is your RPM at WOT?

 

[GA Paramedic]

Re: How fast should a 115 go?

That's a good question. There is no RPM gauge on the boat and I tried to hook an automtive gauge without sucess. in reading some earlier post, I found to where this wouldn't work anyways. And I really have nothing to compare it to by ear so I couldn't even guess.

 

[timmathis]

Re: How fast should a 115 go?

Just a guess 30-35 mph. It really depends on how much weight is on board.

 

[GA Paramedic]

Re: How fast should a 115 go?

I was getting like 25-30 mph. I question the gauge but, again, have nothing to compare it to. I just would have thought that a 115 would do better than that.

 

[studlymandingo]

Re: How fast should a 115 go?

When you say it got on plane with a little help, what does that mean?

 

[05GlastronSX]

Re: How fast should a 115 go?

lets not forget that your 115 inline 6 merc is crank rated, not prop rated. That being said, your 115 in reality is only producing between 90-95 h.p at the prop. If you were to buy a 115 outbpoard AFTER 1986 then you would get a true prop rated engine which would be noticably stronger than your inline even though your inline is a 6 cylinder. you should be wondering how well a 90 does on that 18 foot boat, not a 115 and IMO 30 mph w/ a 90 is not too far off for an older 18 footer.

 

[GA Paramedic]

Re: How fast should a 115 go?

I cleaned the carbs and fuel pump and tried it. It would drag it's butt in the water and that was it. I broke my timing belt just checking it and replaced it. I tried it and it throttled up like it wanted to jump out of the water and then acted like it was starving for fuel before it got up. I adjusted the timing belt notch by notch and found the optimal notch for best preformance. (only had to adjust 4 times.) But still, it took a while and some finness (<-sp?) with the throttle to get it to plane. And I still couldn't find any sweet spot in the throttle like it was flodding out or anything. Once it was up, no more hesitation until you tried to turn with it and put it under a load then the hesitation again. Compression is all equal around 120. fuel pump still looks good as well as the carbs. The fuel tank vent is wide open. The stator is puting out around 360v ac and wiring diagram is checked to be accurate. I don't think I am over propped with a 19p. It idles like a champ and starts even better.

 

[Clams Canino]

Re: How fast should a 115 go?

You ARE overpropped with that combo. Go down to a 17p and it'll come out of the water better, if you actually wanna pull tubes and skiiers use a 15p.<br /><br />The CORRECT position for the belt is to lign up the little nib on the lower 1/2 of the pulley with the little nib on the crankcase just as the motor is approaching TDC on #1. Have the timing just a little too advanced and you'll kill it dead via melting pistons. After you have the belt correct, use a timing light and set it up right. Only once it's correctly set up can you accurately determine prop pitch.<br /><br />You're guessing at too much stuff that needs to be exact.<br /><br />-W

 

[timmathis]

Re: How fast should a 115 go?

Take Clams advice. He knows best!

 

[caldog101]

Re: How fast should a 115 go?

I own a 1976 20 foot "19.6" seacraft with a 1984 in-line 6 115 hp top speed with one person and 6 gallons of gas turning a 13 1/4 x 17 aluminum prop is 38 mph on the gps<br />boat weighs 1600 lbs<br />i weigh 195 lbs

 

[roger3645]

Re: How fast should a 115 go?

I also have a 17p prop if you would like to try it. I also live in Marietta. rip3645@hotmail.com

 

[GA Paramedic]

Re: How fast should a 115 go?

Roger, look for an email! THANKS!