4cy to 3cyl Should I?

[healey8390]

If youve read any of my posts youll know i blew my 83' 4cyl 90 chrysler and its torn down waiting to hear the verdict from machine shop. Did some searching to see whats out there and found an 86 force 85hp rebuilt powerhead ready to bolt and go. My boat is 16ft but its old (79' welcraft airslot165) and goes 33 on smooth water at 4600-4800rpm. Do yall think the 85 would manage? Guy was nice when i called and said it should be the same if not a tad better because inline engines with odd cylinders are more "torqy" then even???? He did not sound like he was giving me the sales pitch he was strait forward and said im not telling you its going to be like a 150 lol! the Reason I ask is because hes selling for great price. But i dont want to under power because its not too fast to begin with. Thanks!

 

[proshadetree]

Re: 4cy to 3cyl Should I?

Im not wild about force engines but if its cheap and he will let you run it. I dont think you will be underpowered my dad had a Johnson 85 on his 16 ft bomber and it run 30 to 40ish.

 

[healey8390]

Re: 4cy to 3cyl Should I?

Yeah but i THINK the 85 johnsons are 4cyls. I just dont want to wind up with a go cart motor in an Abrams tank lol!

 

[Frank Acampora]

Re: 4cy to 3cyl Should I?

OK! here's actual results comparing a 3 cylinder to a 4 cylinder:

Boat: 15 foot Glastron V153 closed bow runabout. Boat in the avatar with the 4 cylinder engine

Engine #1: 3 cylinder 90 HP Chrysler, ported and carbed, polished reed plates--puts out about 105-110 HP. runs the boat at 45 GPS top speed.

Engine #2: Chrysler 4 cylinder 105 with 120 carbs--(somewhat Like your 90)

Runs the boat at 45 GPS top speed--same as the built-up 90 ---BUT--- Due to the higher torque of the 4 cylinder engine, the hole shot is much faster. The boat actually "pops" out of the hole and with one bounce is on plane. Guy was talking out his butt and doesn't know his a** from his elbow. 4 cylinder Chrysler and Force engines with 25 % more displacement and 4 power pulses every revolution ALWAYS have more torque than three. "Ain't no replacement for displacement."

The 85, being a later model will probably perform only a tad weaker than your 90 but the hole shot definitely will be worse.

So: If the deal is good enough it might be worth the money until your engine is running, but I would be willing to bet that after fixing your engine, you will sell the 3 cylinder 85 or use it for something else.

First photo is the 90 with a 75 hood, second is the same hull with the 105, and the third is showing porting of the three cylinder block.

 

[healey8390]

Re: 4cy to 3cyl Should I?

great feedback, thanks everyone

 

[proshadetree]

Re: 4cy to 3cyl Should I?

Guy was talking out his butt and doesn't know his a** from his elbow.

Just exactly who was talking out of their butt?

 

[Frank Acampora]

Re: 4cy to 3cyl Should I?

Oh, I suppose I was---'cause I don't know anything about these engines.

I call them like I see them. When someone is blowing sunshine up healey's butt I'm going to let him know. Similarly, when I hear a statement which contradicts the laws of physics, engineering, and good common sense (which isn't so very common) I'm going to say something.

 

[proshadetree]

Re: 4cy to 3cyl Should I?

So 5 horsepower makes or breaks a boat? WOW new to me. Do you know if his 90 was even tuned right? That 85 might smoke it. He never did say why he lost a piston in his old mill. Running lean maybe? So with all the variables unknown you have a magic answer hey? I like torque same as anyone but I like the water better. If I can afford one way and cant the other I do the one. We all would like a Yamaha vmax 250 strapped to our boats to fly but some times we have to run a pissy old Merc

 

[Frank Acampora]

Re: 4cy to 3cyl Should I?

Re-read my post AND UNDERSTAND it before you rant---nuff said no further replies.

 

[healey8390]

Re: 4cy to 3cyl Should I?

Im sure Frank was referring to what i said the seller told me about odd numbered inline engines are more torqy

 

[jerryjerry05]

Re: 4cy to 3cyl Should I?

If you don't like what someone posts,keep it to your self.These posts are the opinion of the poster and usually aren't up for debate.These post are from usually years of experience.
If you don't agree then post your opinion and leave it at that.The SELLER was talking out his butt, not Frank.
No way a 85 is gonna be as good as a 120.
3cyl or 4cyl.
If the performance was the same they wouldn't make a 4

You can put the 85 head on, then you'll need to re prop,you will not get the results your used to.
Look around there are lots of 120 power heads out there.Look on Craigslist.

 

[Frank Acampora]

Re: 4cy to 3cyl Should I?

BTW Healey: The reason I used my 105 as a comparison is because in 1982 when ALL manufacturers were required to use propshaft horsepower ratings, Chrysler simply de-rated the 105 to 90 horsepower. Same exact engine, different HP rating. That is why you have a 4 cylinder 90. In prior years, the 90 was a 3 cylinder engine.

S'matter of fact, the 4 cylinder 90 is on the cover of the Clymers manual--at least the earlier manuals.

 

[beckspop]

Re: 4cy to 3cyl Should I?

Let me just take a moment to say thank you to Frank for all the info he has shared on this site. As my Dad use to say, "he's probably forgotton more about boats than most of us will ever know..." Keep doin what you do. Thanks again...