Force 150 HUGE difference from 125

[Shifflett115]

I have a 1985 bayliner cuddy , it had a 1985 force 125 on it , the top speed was 33mph at 5000 rpms wot , I bought a 1990 force 150 d model for cheap with a bad lower unit , I put a 176:1 lower unit on it from a 1977 Chrysler 135 , NOW my top speed is 48 mph at 5200 rpms , it acts like a different boat !!!!!. Much better out of the hole and just a lot more all around performance , my question is , will the 176:1 lower unit hold up to the 150 for a good period of time , the 150 had a 2 price drive shaft lower unit on it , should I put a stock unit back on it or will the 176:1 unit hold up ??????

 

[pnwboat]

The gears/bearings in earlier 4 cylinder lower units are not as big/strong as the units that originally came on the 150HP motors. I would expect the it will not last very long, but I guess it depends on how hard you run it.

 

[Shifflett115]

I found a early 90s 90 hp force for sale with a good lower unit for cheap , the lower unit on it looks identical to the one that was on my 150, will it work ?

 

[pnwboat]

Looks like the 1990-1994 1.93:1 ratio lower units that were used on the 90HP and 120HP motors are the same as the one on the 150HP motor. However, there are 2 versions of this lower unit. The one that you don't want has a one piece drive shaft and holds 22oz of gear oil. The one that you do want has a two piece drive shaft and holds 35oz of gear oil.

The 1.93:1 gear ration is better suited to the power band on the 4 and 5 cylinder motors. In most cases, you'll see an improvement in performance verses the 1.73:1 ratio in the earlier motors depending on your prop pitch.

 

[Frank Acampora]

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The 150 has equal length exhaust runners, that's why the exhaust cover is so large. It also has an extra cylinder and between the two, yes, it will make the 125 look sick. The limiting factor in the lower unit is actually the size of the gear teeth. There is a factor called beam strength. Because the teeth press against each other in various spots while turning, they tend to have a high point loading. This can cause them to break if they are not thick enough to withstand the load.

The 1.76 has approximately the same tooth size as the 1.93, the forward gear tapered roller bearing is not much smaller, and the reverse gear thrust and roller bearings are the same as the 1.93. Additionally this lower unit was used on the 4 cylinder 140 and 150 Chrysler. Thus it should work well. should last well. HOWEVER the 1.93 dual exhaust lower unit will actually increase performance a bit over the 1.76 so eventually you will want to replace it.

 

[Frank Acampora]

No Title

Now, if you want real performance, try to find one of these V6 Chrysler engines!

 

[Shifflett115]

Wow i never knew Chrysler made a v6 outboard ! the lower unit im looking at has the water inlets up on the lower unit, not on the torpedo so im guessing that unit is a deul exaust unit, it looks identical to the one that came on my motor , thank you frank and everyone else for all your input, it really helps !

 

[Frank Acampora]

It was never a production engine and I never saw it until about a year ago when someone (I don't remember who, possibly Nordin) sent me the photos.

 

[Scott Danforth]

didnt the motors change rating from crank rating to prop rating about 85 as well? the 1990 motor is definately prop rated. the 85 may have been crank rated.

 

[SkiDad]

Wow! That is quite a jump in the performance. Your old 125 must've been pretty tired. I have almost the same boat as you except it's not a cuddy and stock I was able hit 40 miles an hour with a 17p prop with the original lower unit @4800. I've changed a lot things on my boat now to make a pull harder so I don't have the speed I used to. Well I could, but we are into pulling multiple skiers.

So looking at your numbers were you running a 13p on the 125 and now a 19p on the 150 ?

Is your boat rated for 150 ?

 

[Shifflett115]

I was running a 15p 4 blade turning point prop on my 125 and getting 34mph out of it , i put the 15p on my 150 and was turning at 6000 rpm , i put a 19p 3 blade on it with a 1.76:1 lower unit from an old Chrysler 135 and got 48mph at 5200 rpms and pulled real hard out of the hole ! I am getting the 1.93:1 lower unit that came stock on the 150s so Im trying to figure out what prop i have to run with that lower unit, i was thinking Im going to have to go to a 21p 3 blade or a 20p 4 blade .My boat is rated for a 150 .

 

[Frank Acampora]

Before you go buying another prop try the 19 pitch. The difference between gear ratios is only .17 and I don't think this will make much of a difference on the 5 cylinder engine.. This should not raise the RPM more than 200 so that would still put the engine at the top of its operating range. Then, if you are not happy with performance try a stainless prop in a higher pitch. You may need to vent it to preserve hole shot.

Currently I have a 150 on a 21 foot cuddy cabin rated for 180. I use a 19 pitch stainless vented prop and on a good day will get 43 top speed but quite honestly I don't remember at what RPM

 

[Frank Acampora]

No Title

This prop came with the engine (bought for 300 bucks with 2 bad pistons) It gives me good performance so I never bothered to change it. It appears to possibly be a Mercury prop and has a slight cup on the trailing edges in addition to small venting holes for a better hole shot

 

[Shifflett115]

Well it looks like im prop shopping, took the boat out yesterday with the 1.93:1 lower unit on it and with the 19p 3 blade it over revs quite a bit, at full throttle it shoots to 6000 rpms pretty quick and slips really bad out of the hole and all the way around, I really want to go with a 4 blade on it because we do alot of wakeboarding, tubing ect .

 

[SkiDad]

i think Frank mentioned at one point he tried a dual exhuast lower and it had slip on takeoff and corners that the other lowers did not - not sure why that would be. what kind of prop was your 19p ?

 

[Shifflett115]

It is a qui ksilver 13.25 by 19 , I'm looking for a 21pitch to try now

 

[Shifflett115]

Ok guys i found a mercury laser 2 13.25 by 22p stainless prop for a good price, with the quicksilver 13.25 by 19p my rpms were 6000 wot , do you think the 22p will put me between 5100 and 5500 rpms wot ?

 

[Frank Acampora]

When comparing stainless to aluminum, especially two different designs, it is very difficult to predict what difference there will be in performance. It is safe to say the stainless will drop RPM, but by how much is a different story.

Generally, if you switch from aluminum to stainless of the same design and pitch, RPM will increase by about 200, If you increase pitch by 2 on the same prop, RPM will drop by about 400. THUS, if you went from a 19 to a 22 in aluminum prop, you would expect about 600 RPM drop. Not knowing the Lazer I can't predict how much RPM will drop or even if MPH will increase. Perhaps they can guess better on the prop forum where you have the same question.

Is your current aluminum prop cupped? If not, simply cupping it will decrease RPM by about 200 and increase holding in corners and hole shot.

What is your "good price" on the Lazer? Makes a difference if you want to gamble and experiment.

 

[Shifflett115]

My current prop is cupped , my good price is $125 , but i would hate to buy it and not reach 5000 to 5500 rpms

 

[Shifflett115]

Just talked to millers island propeller company and they told me I would drop 600 to 700 rpms going to the 22p stainless , that would put me right where I need to be