Slow Speed

FRANK JENKINS

FRANK JENKINS

Recruit
Joined
May 4, 2012
Messages
3
Hi All,

New to the Forum, I have a Conquest 1989 16' Runabout, I have a Mercury 110 hp 1966 1100ss 110HR Six, it has I think a 15" pitch x 12" Prop, It seems to travel only about 15 or 20 mph tooo slow, The Bow is not Plaining properly either but Im working on that next time out but its speed is really bothering me for a large motor the Boat is 900lbs without Passengers any Idea's ON solution to problem. I have someone telling me to go to 23" pitch but that would really drop rpms would have to see what rpms are next time to see how much I can change it.:facepalm:

Frank Jenkins
 
coastalrichard

coastalrichard

Lieutenant
Joined
Apr 6, 2009
Messages
1,255
Re: Slow Speed

Frank, welcome to the forums...that seems to me to be a large jump in pitch. Maybe warranted but you need to get a prop that will give you close to your max WOT rpm range while handling a typical load. Four folks, a cooler plus gear...650-700#s...maybe something a bit steeper. You've got sufficient HP just need to get the prop dialed in.
 
S

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Slow Speed

Welcome.
Just to avoid confusion prop size is always given diameter X pitch.
You should read "read this first" at the top of the prop forum.
The key numbers we need is the wide open throttle rpm and speed by gps.
While your prop may not be right;
Based on your speed I would suspect a motor or setup issue.
If the boat lays down like its glued to the water your bottom may be deformed.
A a motor with 15" prop with a speed of about 20 would be turning about 3,000 rpm.
So again while the prop may not be right its not likely the reason for your very low speed.
 
FRANK JENKINS

FRANK JENKINS

Recruit
Joined
May 4, 2012
Messages
3
Re: Slow Speed

FRANK JENKINS said:
Hi All,

New to the Forum, I have a Conquest 1989 16' Runabout, I have a Mercury 110 hp 1966 1100ss 110HR Six, it has I think a 15" pitch x 12" Prop, It seems to travel only about 15 or 20 mph tooo slow, The Bow is not Plaining properly either but Im working on that next time out but its speed is really bothering me for a large motor the Boat is 900lbs without Passengers any Idea's ON solution to problem. I have someone telling me to go to 23" pitch but that would really drop rpms would have to see what rpms are next time to see how much I can change it.:facepalm:

Frank Jenkins
Click to expand...

ps: I Found the pinion is 14 teeth and other is 28 fwd and 2:1 ratio as other eng. RPM 4800 to 5200 prop is approximately 12" diameter and has a 15p stamped on the prop. on the trim first time out I had it about level and next time out I will try it all the way down and work up. Bottom looks fine nothing out of ordinary looks normal.
 
S

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Slow Speed

You wouldn't be the to not realize your are running on 5 or even 4 cylinders.And you probably realize you have 3 carbs
that need to be synced and adjusted right.It also uses a distributor that has a cap and rotor and needs to be timed right
Carb linkage needs to be synced with the timing advance
 
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