Having Trouble Getting on Plane! 1974 Chrysler on a 1991 16 foot Rinker

[hbryant123]

With two people, a cooler, and a half tank of gas My boat will take off and plane out just fine! with two extra people adding about 300-350 lbs it struggles to plain out, i have power tilt and trim and i am not 100% sure how to effectively use the Trim. The engine is a 1974 chrysler 104 with a 13x19 prop i believe, it runs smoothe and starts great. If the extra people are in the back its very very hard to reach plane oif the are in the from its not so bad. I am looking for pointers on what to do to improve the issue. I have played with the idea of hydrofoils and stowing away gear (ancors battery etc) in the front.

 

[Frank Acampora]

Get a newer and bigger engine! LOL. Actually your engine is only delivering about 90 horsepower. Add to that the fact that that particular lower unit is very inefficient and you have a lot of wasted horsepower.

Now when trying to plane with a load tuck the trim all the way in--that is, bottom of the engine closest to the transom. As the boat comes onto plane feed in some up trim until the prop starts to ventilate--you will hear the difference--then trim down slightly.

If you can find an 18 spline thrust pin prop 13 X 17 pitch. try using that when you are carrying a load. Top speed will suffer a little bit but time to plane should improve. Anyway, if you want to ski or wakeboard you would need the 17 pitch prop..

Now, typically you would want to have a tachometer and check full throttle RPM. The correct prop will let the engine rev up to about 5000 RPM--the middle of the recommended range of 4500-5500 (this info is printed on the serial and model number plate located inside the cowl near where the control cables come in.

To help with some perspective, with a 19 pitch prop and a full load, it is like trying to start a car moving in high gear rather than low.

You know my opinion on hydrofoil use from the Force forum. Understand that even if it does help you MIGHT lose a couple of MPH top speed. Then again,

 

[Maclin]

The smaller the boat the more likely you gotta move people around to take off when loaded. I used to boat with a 15.5 foot and 55hp and moving people forward was just a fact of life, especially with a fixed motor position and no trim on the engine.

Right now I boat with a 16ft bowrider with 90hp and 17p prop. That can plane us out loaded with no problems and not have to think about moving around first. It can spin a 19p and with just me in it works ok, but for most of our boating the 17p is better all around.

 

[hbryant123]

Get a newer and bigger engine! LOL. Actually your engine is only delivering about 90 horsepower. Add to that the fact that that particular lower unit is very inefficient and you have a lot of wasted horsepower.

Now when trying to plane with a load tuck the trim all the way in--that is, bottom of the engine closest to the transom. As the boat comes onto plane feed in some up trim until the prop starts to ventilate--you will hear the difference--then trim down slightly.

If you can find an 18 spline thrust pin prop 13 X 17 pitch. try using that when you are carrying a load. Top speed will suffer a little bit but time to plane should improve. Anyway, if you want to ski or wakeboard you would need the 17 pitch prop..

Now, typically you would want to have a tachometer and check full throttle RPM. The correct prop will let the engine rev up to about 5000 RPM--the middle of the recommended range of 4500-5500 (this info is printed on the serial and model number plate located inside the cowl near where the control cables come in.

To help with some perspective, with a 19 pitch prop and a full load, it is like trying to start a car moving in high gear rather than low.

You know my opinion on hydrofoil use from the Force forum. Understand that even if it does help you MIGHT lose a couple of MPH top speed. Then again,

Thanks frank! After I get my lower end seal kit installed i will search around for a different prop! I read some on here about using a different lower end from a 90hp with the 2:1 ratio and a different prop, is their any truth to this?

 

[Frank Acampora]

Yes, as with the one piece lower unit swapping a 2-1 lower unit on will increase speed (and acceleration) by about 3 MPH. HOWEVER. that will be difficult to find. The two piece 2-1 lower unit was ONLY used on the 90 horsepower engine. That was one of the ways they raised the horsepower from 85 to 90--let the engine rev easier.

The good news is that you are not limited to a 1974 lower unit Up until (I think) 1977 although the two piece lower units looked different, they all had the same bolt pattern and will swap onto the midleg. Dang-- I wish I could post photos.

 

[hbryant123]

Thanks for the info. I checked in my spare parts all i have is a 13x15 prop, ide like to try a 13x18 or 13x17 prop, any idea on how to come across these old props?