Original factory prop size of 79' Chris Craft 28' Express Cruiser

[lonerinalaska]

I am trying to find out the original factory prop size as well as any recommendations for what I should be using now. I have almost all the original paperwork/manuals for everything that came with the boat or was done afterwards, but there is nothing that says what propeller I should use or what speeds I should be attaining. The internet hole was not very forthcoming either.

1979 Christ Craft 28' Express Cruiser
Twin GM 181FL engines (both which are original and rebuilt a few years ago and have maybe 350 hours put on since)
130 HP @ 4600 RPM, 170FT LBs @ 3300 RPM, 4" bore, 3.6" stroke
Ratio of 1.5:1
wet weight 7125 lbs
Velvet drive transmission, both left hand turning
Current props 14X11 ( Not sure of material since it is hard to tell with the corrosion, but they look like bronze)
WOT appears to be 4600 RPM @12.1 GPH (haven't tested that, but according to manual)
I cruise at 3600 RPM @7.0 GPH

I've only owned this boat a short time, so my experience with it is limited. Due to the age of the engines, I would really prefer to keep them at or below 3600 RPM. However, I am only getting about an average of 10-11 mph (against the tide). The boat doesn't seem to get on step, even if I adjust the trim tabs. The propellers are old and possibly even original. I am hoping to be able to achieve 15-18 mph to make my commute home an hour versus an hour and a half. I don't want to do any engine mods and I'm not sure there is enough room to put a pair of 350's in it, so at best, when it is time to replace the engines, it will be with the same size.

If anyone can shed any light on the prop size or cruising speed, that would be great.

 

[alldodge]

Howdy

The old Chris is a great boat, solid and well made for its day. The issue is trying to get speed out of the boat is real hard. They have a modified V hull and not made to really plane. The boat at your speed looses more then half of its forward speed due to prop slip. The 4600 rpm WOT is where I think it should be. You could pull the props and have them cleaned and tuned. The prop work will help some but will not make you 1/3 faster.

If the hull is not smooth, then this would be my second place to do some work. Like all boats, there is no replacement for displacement. The best way to increase speed, not the cheapest is more HP

 

[Scott Danforth]

those old chris crafts were slow. they putt along just fine, however most had a single V8. the twins would be nice, however i would go with twin diesels

 

[lonerinalaska]

The main reason I thought there must be a reason for why we are topping out at about 11mph was because every other model of Chris Craft boat I looked up of the same year, showed a cruising speed of around 17-18 and a max speed of low to mid 20's. Even the 35'+ boats showed cruising around 18. The hull needs painting fairly soon, but it is clean. The props have seen better days and I will be replacing them as soon as I can get a confirmation on the factory supplied size. I would love to drop a pair of 350's in there, but I don't think there is enough length in the engine room.

 

[lonerinalaska]

One other quick question, any ideas if running these motors at 3500 rpm is more harmful than say around 4300? The previous owner ran them at 3500 rpm for the 30 years he had and he said the original owner ran it in the 4000's.

 

[alldodge]

You mentioned that WOT is at 4600, so this says your close where you should be. Reducing some on the pitch and getting it to 4800 would be good, but your so close I don't see the gain. As for running at 4000 over 3500, don't see an issue with the motor, but 3800 might make it a tad better