Prop or something else?

[spetroff]

Hello,

I recently purchased a 1990 16.5' Bayliner Capri 1700. The engine is a 1998 Johnson 50hp model J50TSLECC, 2 cyl 2 stroke. According to the specs, the dry weight of the boat/motor is 1200lbs. I don't know what the engine's WOT RPM rating is, but I'm assuming that it is around 5000rpm. Unfortunately the boat does not have a tach. The original prop was a Michigan 012039, which is an 11.75" diameter 17" pitch. The engine runs beautifully, and the boat is rated for 50hp, but it can barely plane with this set up. My Dad took the motor in for servicing at a local Marina, so I've got to assume that there is nothing significantly wrong with the engine, or I would have heard about it.

I installed a Turning Point Hustler 12.5x13 prop and have vastly improved the hole shot and somewhat improved top end speed. So I know that I am now close to the correct prop. One weird issue is that coming right out of the hole, there seems to be a little 'slip'. That is the engine seems to rev slightly higher, then slow as the boat accelerates. Any idea what could be causing this? Also, I'd really like to get a little more torque out of it. I'm worried about decreasing the pitch again, because I don't know where the engine is revving right now. It just seems that the boat rating shouldn't be that far out; it's rated at 50hp, but just barely meets a reasonable expectation of performance (yes I've heard that these boats were underrated). Do I need a tach to test out a new prop? Would it be worth trying out a Turning Point Express 11.75x13 prop? I really don't want a stainless prop, but the next shorter pitch Hustler is 12x10.5 and that seems a large drop in pitch. Any other suggestions? Thanks

Shane

 

[steelespike]

Re: Prop or something else?

Thats a lot of boat for a 50.
You really shouldn't be changing props without a tach.Perhaps you could get
a tiny tach; reasonable, easy to install and will fit any similar 2 stroke.
Dropping to the 13 would give you about 800 rpm.The 17 was probably a bit too much but you need to get a handle on your rpm.For the health and efficency of your motor.I wouldn't run wide open top end till you know where your at.What did you mean by "a little more torque"
If your looking for more hole shot you could play with the trim.Trim in a little.
you could get something like smart tabs.Tabs will get on plane easier and stay on plane with less throttle.

 

[JoeCrow]

Re: Prop or something else?

A 50 does sound small for that boat
What's the transom rated for?

 

[Silvertip]

Re: Prop or something else?

I can assure you the 13P is wrong as was the 17P. That motor wants a 12-1/4 x 15P prop. The 13P is too sensitive to engine height (not trim) so what you are experiencing is ventilation that may be corrected by lowering the engine a hole or so. I know that from experience with a similar setup. However, as was mentioned, that engine is on very bottom of the HP range for acceptable performance. The boat is probably rated for a 75 HP or possibly even a 90 HP motor.

 

[spetroff]

Re: Prop or something else?

The rating is for 50 hp as indicated by both Bayliner and the DOT sticker (I'm assuming the DOT issues them, the boat is a long ways away right now). They originally came with a Force 50, which is reputed to have less power than the current Johnson. As well, I had a Michigan 012038: 12.25x15 on there and it's performance was almost indistinguishable from the 17. So the 13 seems to be the correct choice. I can certainly look at lowering the motor though. It doesn't cavitate on turns though, at least not the ones I've put it through so far (I probably haven't pushed it too much)

Thanks for the tip about the tiny-tach, it will definitely add some confidence to see where I'm revving at, without having to dredge up shop manuals for the engine (Johnson have a pitiful amount of info online...)

Shane

 

[Beefer]

Re: Prop or something else?

I have a 1994 Bayliner Capri 1605 (15'7"), with an original 70hp Force. My owner's manual says I can put upto a 90hp on the boat. I agree, the 50 doesn't seem to be enough. I get on plane almost immediately, and my top speed is 30+mph (says the GPS). I have no idea what prop I have (just got the boat last weekend), but it looks stock to me.