'74 Chrysler 135hp Prop help needed

[Sterno]

I'm running a '74 Chrysler 135 (1.78 gear ratio) on my '77 Glastron 188SSV. Top speed is about 34 Mph at 5000 rpm, prop is 16" pitch. I could easily rev the motor to 6000+rpm. FSM tells me that the motor should have come with a 19" pitch prop, so someone probably changed it.

Seeing that the 18 spline props are out of production and a bit tricky to come by I thought Id ask here for some recommendations for what pitch prop to look for before I buy one. The boat is usually only lightly loaded (me and fishing gear)
Thanks

 

[Maclin]

Re: '74 Chrysler 135hp Prop help needed

It definitely sounds like you are underpropped. Using the figures you gave for MPH, RPM, and drive ratio as a baseline a 19 would get you to 40mph and a 21 would get to 44mph.

Not knowing a whole lot about the boat I would recommend a 19 pitch since that is how the OEM shipped it. A 19 would not overprop in my opinion where a 21 might. Post more about the size of your boat.

 

[Sterno]

Re: '74 Chrysler 135hp Prop help needed

Thanks for the quick reply, the boat is a 18 foot 8 inch Bowrider, Deep V hull, here's a link to the sales brochure
http://www.classicglastron.com/77gl-v188-189.html
It trailers fairly light but haven't put it across a scale, I'm guessing around 1200lbs with a full tank.

Another thought I had was replacing the lower unit with a later 15 spline one, I'm guessing it would bolt up as Chrysler/Force seemed to not change their designs much.

 

[Maclin]

Re: '74 Chrysler 135hp Prop help needed

Sterno, I bet you will find lots of help with that lower unit swap in the Force & Chrysler Outboards section.

I have a soft spot in my heart (some say in my head!) for the Chrysler outboards

 

[Frank Acampora]

Re: '74 Chrysler 135hp Prop help needed

You can not replace the two piece lower unit with a later one piece lower. You must get a midleg if you want to do that.

Turning 5000 RPM now do not go up in pitch you will lose RPM and speed.

Repost over on the Force forum and I will give you detailed instructions on replacing the midleg and lower unit to get better speed. You should ne able to get 5-8 MPH more.

 

[Maclin]

Re: '74 Chrysler 135hp Prop help needed

Frank, I took it from his first post that he could go on past 5k to 6k rpm now, that is what makes me think he can maybe go up a step or two.

 

[Frank Acampora]

Re: '74 Chrysler 135hp Prop help needed

Ah, yeah! I missed that! Call it getting up too early. Or getting too old too soon. He probably could use a 19 pitch prop if he can now get to 6000 and he will gain speed in the bargain. Unless it is an aftermarket prop, pitches usually were odd--15, 17, 19. Thus a 19 pitch will give about an 800 RPM drop over a 15 pitch.

However, the one piece 15 spline lower unit IS about 3 MPH faster by itself. I proved that a couple of months-- maybe a year ago by swapping a midleg and one piece lower onto an older engine and wrote it up over on the force forum.

 

[Maclin]

Re: '74 Chrysler 135hp Prop help needed

...and then he can have a better prop selection/availability too, right? Interesting....

I am staying in this topic because I can tell that I will end up with a 70's Chrylser tri-hull with Chrysler O/B someday for nostaligia's sake, I can just feel it....

like i said before, soft spot in my head...

 

[Frank Acampora]

Re: '74 Chrysler 135hp Prop help needed

Yeah--better prop selection and the props are better--thrust washer instead of having a 5/16 diameter pin take all the thrust loads.

However, if you look hard enough you can get some interesting pin drive props for the 2 piece lower. I have a bronze 4 blade and two 2 blade solid hub OJ bronze racing props. One 19 and 0ne 21 pitch. I also have a couple of stock 2 blade aluminum props.

I do have a soft spot for the 77-78 two piece. It had a nice taper from the midleg to the cav plate and a nicely shaped large cav plate. If you get into a bind, the earlier units will bolt right up and perform about the same but they look "clunky." All internals will swap though.

Unfortunately i do not have a photo of it, only a used prop

 

[Sterno]

Re: '74 Chrysler 135hp Prop help needed

Thanks for all the info and advice.
I only got this Boat rigged and in the water last week. It's also my first boat, running and on the water for about $1200 (Boat, Trailer and Motor).
A mid-leg replacement sounds like a winter project so for now I'll just stick with what I have and keep my eyes out for a prop at the wrecker's.

If I come up with another solution, I'll be sure to post it.

p.s here's a pic. not real pretty, but iy is functional

 

[Maclin]

Re: '74 Chrysler 135hp Prop help needed

Sounds like a good plan, nice score too it seems

 

[Sterno]

Re: '74 Chrysler 135hp Prop help needed

UPDATE.
After a lot of searching I've finally found a good prop at a low price. 19" pitch gives me 30mph cruise @4300rpm and a WOT speed of 39mph @5100rpm. I don' think I want to go any faster in this old thing anyways.