Top speed Help

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hbryant123

Petty Officer 2nd Class
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I have a 1974 105hp chrysler i put on a 16 foot v170 rinker. Right now my top speed is about 37-38 mph. Is that about right for my set up??? How can i make it hit that magic 40mph mark???
 
jerryjerry05

jerryjerry05

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Re: Top speed Help

37-38 is pretty good for a 105.
To make sure the motors performing?
Tach?
RPM's at WOT??
Pitch of the prop?

To get a bit more speed.Figure out the pitch,say it's a 17p go to a 19p.
It will go a bit faster but can use up to 20% more fuel.
These Chryslers use enough fuel as they are:)
 
Frank Acampora

Frank Acampora

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Re: Top speed Help

fathers day and vacation 064resized.jpg102_6448.jpg102_0245.jpg102_6415.jpg102_6414.jpg

Right now, 35-38 sounds about right for top speed. There are a couple of things you can do to gain some RPM and speed. These photos show a 105 on a later midleg. This 15 foot boat tops at 45 MPH with mods 2 and 3.

1. Look around for an early model (earlier than 1978--76-77 looks nice) Chrysler 90 junker or lower unit. The lower unit is 2 to 1 ratio and will bolt to your engine leg. Using the 2 to 1 ratio lower unit with an increase of 2 pitches on the prop will give somewhere between 3-8 MPH more.

2. Replace the manifold covers and WB carbs with manifold covers and TC carbs off a Chrysler or Force 125. Top speed won't improve much but hole shot will be better. This is an easy bolt-on modification. You may need to make a couple of gaskets though. Be absolutely certain that the carbs are synchronized, clean, and the low speed needles are set correctly--see the sticky FAQs at the top of the forum.

3. Swap your powerhead onto a post 1979 midleg and lower unit. In past posts I have shown that this will yeild about 2 MPH more (with the correct prop.
 
H

hbryant123

Petty Officer 2nd Class
Joined
Jun 18, 2012
Messages
139
Re: Top speed Help

jerryjerry05 said:
37-38 is pretty good for a 105.
To make sure the motors performing?
Tach?
RPM's at WOT??
Pitch of the prop?

To get a bit more speed.Figure out the pitch,say it's a 17p go to a 19p.
It will go a bit faster but can use up to 20% more fuel.
These Chryslers use enough fuel as they are:)
Click to expand...

Yea i felt like that speed was sufficient enough. Yea my beast does use some gas at top speed! it seems to get its best fuel mileage at 20-25 mph. As for the prop its a 13 by 19, its the origional prop and its a touch chewed up. As for wot rpm idk because i havnt installed my tach yet. should it run top speed at 5500 rpm?
 
H

hbryant123

Petty Officer 2nd Class
Joined
Jun 18, 2012
Messages
139
Re: Top speed Help

Frank Acampora said:
View attachment 159330View attachment 159331View attachment 159332View attachment 159333View attachment 159334

Right now, 35-38 sounds about right for top speed. There are a couple of things you can do to gain some RPM and speed. These photos show a 105 on a later midleg. This 15 foot boat tops at 45 MPH with mods 2 and 3.

1. Look around for an early model (earlier than 1978--76-77 looks nice) Chrysler 90 junker or lower unit. The lower unit is 2 to 1 ratio and will bolt to your engine leg. Using the 2 to 1 ratio lower unit with an increase of 2 pitches on the prop will give somewhere between 3-8 MPH more.

2. Replace the manifold covers and WB carbs with manifold covers and TC carbs off a Chrysler or Force 125. Top speed won't improve much but hole shot will be better. This is an easy bolt-on modification. You may need to make a couple of gaskets though. Be absolutely certain that the carbs are synchronized, clean, and the low speed needles are set correctly--see the sticky FAQs at the top of the forum.

3. Swap your powerhead onto a post 1979 midleg and lower unit. In past posts I have shown that this will yeild about 2 MPH more (with the correct prop.
Click to expand...
Thanks for the input! Honestly for this year i might just get a prop that is in good shape and ride it out this year!
 
jerryjerry05

jerryjerry05

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Re: Top speed Help

Get yours redone.Usually cheaper and sometime only takes a week.
Check at any local shop/marina.Someone rebuilds them.J
 
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spool

Petty Officer 2nd Class
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Oct 11, 2011
Messages
126
Re: Top speed Help

i went out today and was able to get to 41mph with a 105hp and a 17pitch prop on a 14ft so yeah on a 16ft that speed sounds good :)
 
jerryjerry05

jerryjerry05

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Re: Top speed Help

On the motor somewhere is a sticker/tag that tells what the max rpm's are at WOT.
Usualy these Chryslers, is max 5200-5500.
Rebuilds $45-70 depends on the shop.
 
SweeperForce

SweeperForce

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Feb 7, 2010
Messages
487
Re: Top speed Help

I think I read somewhere that a stainless steel prop will give you an extra 4-5 mph. The only thing is they are pricey.

Tom
 
Frank Acampora

Frank Acampora

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Re: Top speed Help

Finding props for that 18 spline propshaft is difficult enough. Although they were made, Stainless would be rarer than hen's teeth and even more difficult to find. OP would need to be very lucky to find stainless. The best he could hope for would be a decent condition Bronze prop--either used or NOS.

On these engines, 4-5 MPH is out of the question. With a Bronze prop, 200-400 RPM gains are usual with a corresponding speed increase of 2-4 MPH.
 
H

hbryant123

Petty Officer 2nd Class
Joined
Jun 18, 2012
Messages
139
Re: Top speed Help

jerryjerry05 said:
On the motor somewhere is a sticker/tag that tells what the max rpm's are at WOT.
Usualy these Chryslers, is max 5200-5500.
Rebuilds $45-70 depends on the shop.
Click to expand...

Yea i checked my engine plate and its 5500. I also checked with my local shop for a prop redew they said they send them off and its like 100 dollars. I might just get a good used one for 70 on ebay.
 
H

hbryant123

Petty Officer 2nd Class
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Messages
139
Re: Top speed Help

spool said:
i went out today and was able to get to 41mph with a 105hp and a 17pitch prop on a 14ft so yeah on a 16ft that speed sounds good :)
Click to expand...

Yea im pleased with the speed. 41 is awsome! chrysler power!
 
jerryjerry05

jerryjerry05

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Re: Top speed Help

Just remember the WOT!
Shouldn't be more than the 5500.
$100 to rebuild.WAY out of line.
Look around!!!
 
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spool

Petty Officer 2nd Class
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Oct 11, 2011
Messages
126
Re: Top speed Help

hbryant123 said:
Yea im pleased with the speed. 41 is awsome! chrysler power!
Click to expand...

Yeah I'm pretty happy with it, the water was a bit choppy so hopefully it can go faster on a lake thats glass, Sorry my boats actually 12.7ft so yeah the engines quite large compared to the boat.
Here is a video if you're interested.

Luckily I went out on the only good day in winter this year i think! (Australia)

http://www.youtube.com/watch?v=QmqyZHw7Whw
 
H

hbryant123

Petty Officer 2nd Class
Joined
Jun 18, 2012
Messages
139
Re: Top speed Help

spool said:
Yeah I'm pretty happy with it, the water was a bit choppy so hopefully it can go faster on a lake thats glass, Sorry my boats actually 12.7ft so yeah the engines quite large compared to the boat.
Here is a video if you're interested.

Luckily I went out on the only good day in winter this year i think! (Australia)

http://www.youtube.com/watch?v=QmqyZHw7Whw
Click to expand...

Thats a sweet video!
 
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