Prop? 135hp Evinrude v4 / 18 ft Tri-hull

[nuttyxp]

First boat, had it a year, but due to engine cooling probs I only ran it a little last year. Tach doesn't work yet so dont know wot. It was sluggish getting on plane but seem to cruise nicely somewhere in the range of 27-32. Want to use it more for towing skiers or tubes with 4 adults and gear for the day, and am looking for the right pitch to get it out of the water quickly without giving up to much top speed. Here's the poop...

1975 Evinrude 135hp V4
125-135 lbs compression between cylinders
1975 18ft AMF Crestliner Muskie (Tri-Hull Open Bow)
13 1/4 X 17 prop (I think, as 13 1/4 diam only available in 17p thru BRP cat.)
exhaust thru prop
Meadium to Heavy loads expected

Any ideas for me? Also wondering if other models will fit? (saw a few on Ebay)
Any info on this would be helpfull.
Thanks All......

 

[K.P.]

Re: Prop? 135hp Evinrude v4 / 18 ft Tri-hull

Without any RPM information from a working Tach, any prop suggestion you receive will only be guessing and may not provide the performance result you are seeking. Fix your Tach first before you waste money on a prop, then provide the WOT info.

When you do your test, it is best done with only yourself and maybe another person on board and a light load of fuel.

Since you are new to boating, make sure you are trimming the boat correctly. A trim guage is only a reference, not a performance meter. Increase trim until you reach a point where the RPM's continue to climb but your speed does not increase or begins to decrease. Then trim back down a little. That is your Max WOT. Some boats may severly porpoise (bow bouncing) before reaching your max performance threshold. Sometimes that is caused by too large a pitch prop, other times just poor weight distribution, or a combination of both.

 

[SparkieBoat]

Re: Prop? 135hp Evinrude v4 / 18 ft Tri-hull

ditto what KP said. that is what you need to do, also porposing could be caused by a motor too low in the water, you may need to raise your motor. also trim tabs will stop porposing and really help out the hole shot and lessen/stop bow rise at take off. a big help when pulling skiers. your current 17 pitch prop will probably do the job and be the right prop for you. try raising your motor up to the bottom holes, or get a manual jack plate (about $150-400) make sure your prop does not ventilate (catch air) from being too high. get motor as high as you can with out it cavitating/venting , when running wide open trimmed out my fin tab is usually just out of the water. get a set of "smart tab" trim tabs ($200) or even better a set of adjustable trim tabs ($500-600), this will be what you need to do. after you install the trim tabs you may need to lower motor or change prop to a 19. but you cannot properly prop your motor with the RPM unknown.

 

[craze1cars]

Re: Prop? 135hp Evinrude v4 / 18 ft Tri-hull

We have no RPM data, no top speed data, and only a guess of current prop pitch...

As has already been stated, an accurate answer...or even an educated guess...is simply not possible.