Slow boat 65HP Johnson 15ft Starcraft Capri

I have been tinkering with this boat for a couple of years now and have not been able to get anything more than about 7mph. Because of this, I hardly use the boat. I was told by someone who tested the motor that the compression is good on all 3 cyl but that only 2 carbs out of 3 were getting fuel. So I rebuilt all 3 carbs and now all 3 are getting plenty of fuel.

The motor fires right up and idles fine. I do not have a tach set up and do not know how to set one up on the motor. For the life of me I can not find the book i bought for the motor to see if it will show me how to hook up the tach.

Reason for mentioning the tach is because after reading a few posts I believe it is important to know your rpms at fullthrottle and the speed to figure out the difference in pitch needed to bring up speed also with regards to the length of the boat.

The current propeller is a 13.75 x 15. Michigan Wheel p/n 011002

I think I should move to a 13 x 19 M/W- 011004, but I am not 100% sure and do not want to spend the money to find out I am wrong.

can anyone help me figure this out, PLEASE!

the motor is an Evinrude-Johnson 65hp 3cyl pleasure (outboard) 1972-1973
15ft tri-hull starcraft capri

normally holding 2 adults and 1-2 kids approx 450-500lbs

p.s. if you hold onto the prop and pull?push in and out on shaft there is minimal movement, is this normal or terribly bad?

Re: Slow boat 65HP Johnson 15ft Starcraft Capri

Ok, so have gotten a response on another section of the forum stating that the hub could be spun. so I tried to spin it and could not get it to budge. The motor will go full throttle but no speed. I also made a call to a local ship wreck marine and the guy told me that he would run the exact same size prop that I have on it now. So I am back to square one.

Also I was wondering why I have 30+ views but no responses? can anyone help me out?

Here is a video of the prop and me testing the hub. let me know what you think.
http://www.youtube.com/watch?v=2C9eT2_pS1E

Re: Slow boat 65HP Johnson 15ft Starcraft Capri

7mph means that there is more resistance than you can overcome with your hand.....think about it, you would have to spin the prop to push the boat at 7mph...a daunting task by hand .

Remembering OMC back then.....been a Merc guy for a lotta years. Back then I ran a 125 John, kin ran a 60, neighbor ran a 60, friend ran a 65, all OMC engines. Props were 15 to 17P except for the 65 which was a later engine and was on a 16' Kingfisher Bass boat. I think the prop had a nut and a cotter pin to lock it in place. May have also had a flat washer between the prop and the nut.

On the 15' tri hulls, popular in that day and time, the engine/prop selection I mentioned allowed you and your small family to enjoy an outing on the water and could waterski one person with the boat full of the rest of the family. So there's my input on your current prop pitch. My boat was larger and therefore is not appropriate for this answer.

Take the prop off and mark from the hub which is splined to fit on the prop shaft, out to the inner part of the prop itself. You don't have to extend the line out beyond where exhaust comes out.

I don't remember whether it is best to do it on the rear or the front of the prop....do both then at least one will tell you what you want to know. You can't see the rubber hub as it is bonded to the bronze spline (slipping occurs between the rubber and the inside of the prop) and is covered up by the flange on the spline part, but it is between the actual propeller material and the splined hub that mates with the prop shaft. Put the boat in the water and attempt to move forward getting your engine revving and your 7mph.

Go to a suitable place, shut her down and remove the prop, inspecting the line you drew between the splined hub and the actual propeller inner hub material (alum, bronze, or SS). If the line is no longer a straight line, the prop hub line is no longer in alignment with the line you made on the splined inner part, then you do in fact have a spun hub. If your prop is in good physical shape otherwise, have a prop shop re-hub it. If it's all dinged up you might consider a new prop and they sell them on here and have some nice deals.

Until you know otherwise, stay with your current pitch. With my experience of boats being driven by engines such as yours, 19P is way too much for what you want to do and 17 may be more than you want. Your engine will like the 15 better than the others as it will allow the rpm's to run higher which 2 strokes normally like.

HTH,

Mark

Re: Slow boat 65HP Johnson 15ft Starcraft Capri

Search the internet for a TinyTach. Search for cheap price. Comes with instructions and easy to hookup. Or beg, borrow, or rent a 2 cycle dwell tach. Without RPM info no one can help you. Example: if WOT is 1500 ? 2000 RPM then 7-10 mph is probably right and you have other issues you need to fix first. If WOT is 4000-6000 RPM then people will help you determine if it?s a lower unit or propeller issue or other problem.

Re: Slow boat 65HP Johnson 15ft Starcraft Capri

Wow Mark, Thanks for all that information. I figured trying by hand to spin the hub would not make any sense. You are right there is indeed a washer nut and cotter pin to attach the prop. I guess I need to get out to the lake and do some testing as you mentioned with marking the hub. I really do appreciate the help. The prop is in excellent condition otherwise so if it is the hub I think I will definitely try to get it re-hubbed. Unless a of course it costs more than a new hub. I will post on here what I find and hopefully I do find a spun hub as it would be the easiest fix and no more testing everything and figuring it out.

Re: Slow boat 65HP Johnson 15ft Starcraft Capri

labawg said:

Search the internet for a TinyTach. Search for cheap price. Comes with instructions and easy to hookup. Or beg, borrow, or rent a 2 cycle dwell tach. Without RPM info no one can help you. Example: if WOT is 1500 ? 2000 RPM then 7-10 mph is probably right and you have other issues you need to fix first. If WOT is 4000-6000 RPM then people will help you determine if it?s a lower unit or propeller issue or other problem.

Click to expand...

Thanks for the tach info Labawg. I just found a tiny tach that will work for my boat, so now I just gotta find the best price. Thanks again. by the way what does WOT mean?

http://www.jazzmotorsports.com/tiny-tach-hourmeter-and-tachometer-p-38929.html

Re: Slow boat 65HP Johnson 15ft Starcraft Capri

Wide Open Throttle

Re: Slow boat 65HP Johnson 15ft Starcraft Capri

labawg said:

Wide Open Throttle

Click to expand...

Lol, thanks that makes sense now.