105hp normal wot rpm?

S

spool

Petty Officer 2nd Class
Joined
Oct 11, 2011
Messages
126
Hey guys. My Chrysler 105 is running really well, starts first go idles smoothly. Top speed of my 3.7m Haines hunter seems to be 41mph. It gets there quickly and sounds strong, I've set and checked the timing, synced the carbs and make sure they open fully. The maximum rpm I see is 4500-4600rpm, is this normal or should I be seeing over 5k? Its got a 17pitch prop.

Is this normal?
 
Frank Acampora

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: 105hp normal wot rpm?

It can be normal depending upon load. Obviously, on a heavy boat it will not be able to turn a given pitch prop at the same speed as on a lighter boat. If you read the tag inside the lower cowl, you will see that it is rated to run at 4500-5500 at wide open throttle and (I believe) it is rated 105 at 5000.

You would be at the low end of the RPM range but I don't think you want to go to a 15 pitch prop.
 
G

Georgesalmon

Lieutenant Commander
Joined
Apr 14, 2012
Messages
1,793
Re: 105hp normal wot rpm?

If the range is 4500-5500 a 15p would get you to 5000ish. I doubt you would get much if any top end increase. You would get a hole shot increase. At 4600 you are in the power range and should be treating your engine OK. I would try a 15p if my boat.
 
S

spool

Petty Officer 2nd Class
Joined
Oct 11, 2011
Messages
126
Re: 105hp normal wot rpm?

Georgesalmon said:
If the range is 4500-5500 a 15p would get you to 5000ish. I doubt you would get much if any top end increase. You would get a hole shot increase. At 4600 you are in the power range and should be treating your engine OK. I would try a 15p if my boat.
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Thanks, thats what i thought, holeshot is good currently and its smooth all the way to topspeed, I can get a few tubes out of the water very quickly (hydrofoils help too)

I don't have alot of choice when it comes to prop's as the engines a older a 18spline lower unit, I've got 2x 17pitch props for it but the 18 spline ones are incredible hard to find especially in Australia.

it goes pretty nicely as is, i think I'll leave it.

Thanks for the advice!
 
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