Help me so I dont ruin anything please (Prop Install)

[gidds]

I got my new prop in. It is a 13.25" w/ 21 pitch (Turning Point H-1321 w/ Hub 30). I got my old one off and verified the part number and the existing prop was 13" w/ 19 pitch (Michigan Wheel 031043).

I have a 16' Glastron Tri-hull with a Mercury 1350 (1971 135hp). I checked the prop selection guide in the service manual and came up with the following weight: Boat 850lbs, engine 350lbs, 4 persons average 500 lbs for a total of 1700lbs. That is what I based my decision on (13" / 21 pitch).

I called Turning Point to make sure I had the right hub and prop. The gentleman on the phone said that they had both 14.25" and 14.75" gearcase housing models listed for my engine. He stated to pull the old prop off and compare it to the one I have (14.25"). I also slid the prop on and it fit the inner diameter well. It appears that they are the same:

I am assuming that I need to install and verify RPM's.

Can anyone tell me if I have made correct assumptions......

UPDATE!!!!!!!!!

So I went out and cleaned the shaft and tried to prefit everything just to see. IChecked my thrust washer and it apperas to be properly seated on the shaft. I slid the hub on all the way then slid the prop on.....turned by hand and it hits the anode:

So where do I go from here......20 or 19 pitch? other manufacturer?

Now normally I would have slid the prop on and hit the lake......I must be learning something from you all!!!!!!!

 

[Texasmark]

Re: Help me so I dont ruin anything please (Prop Install)

No! Get your file out and file off part of the trim tab or get a high perf tab which is shorter (front of it cut off) and allows for props with more pitch. I filed mine off (filed a notch in it) so that I had about 1/4" clearance between it and the tip of the blades on my current engine......but you have other things to consider:

Now, your numbers. No tach data supplied which would be very helpful. It appears that your old prop was standard issue alum. That means no cupping. The Hustler is cupped which is the equivalent (usually) of adding one inch of pitch. Then you went up 2" in pitch for a total load change on the engine of 3 inches. Expect a 500 to 600 drop in rpm's which could lug your engine, but you don't know since you gave no rpm's with the current rig.

Other thing is your engine is powerhead rated so you really have a 115 hp by today's standards.

The Glastron trihull was a pretty efficient hull but as I recall it had no steps, pads, or offsets that would give you lift with a higher pitched prop which you would want/expect to increase your mph. On some hull configurations, such as mine which has 3 distinct steps to ride on....the faster you go the fewer the steps are in the water) as you increase pitch you put more thrust against the hull and cause it to lift out of the water more which reduces drag allowing rpm's to remain higher than expected and provides for more speed....more pitch more speed....if you are at the right place with the engine's hp/torque curve. Otherwise, instead of increased performance, it lugs the engine and you loose speed and can damage your engine. That I6 did not like to be lugged.....if bad enough it wouldn't even get the boat on plane.

Also I'd bet your gearbox is 2:1 which supports what I am going to say and that is you are over the limit on pitch for that weight on a conventional tri-hull.

Before you install and use your new prop (so that it is returnable if the following fails), you need to know what your WOT rpm's are with your old prop running the load you mentioned.

The I6 Merc I had a top rating of 5500 rpm's but mine ran 6000 and loved it for 7 years and is still running for the current owner. It's a '89 115.....I6's love to run.
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Get your old prop rpm data (if you need a tach they are about $90 at your Merc dealer) and subtract 500 rpm's which would/should represent your rpm's with the prop in the picture. If you aren't up around 5500 at WOT then send the prop back and get a lesser pitch, like the 19 you had but you will still get a 150-200 rpm drop with the cupping of the Hustler, but the cupping will give you increased performance and reduces the tendency to ventilate in turns and rough water.

You got the right prop hub diameter for your gearbox diameter. The larger gearboxes are for the V6 engines.

Also, it looks like the port holes on the Hustler are blocked by pop rivets. Why? Did it come to you that way? The holes are ports which help to improve your hole shot. Unless they cause you problems, you want them open.

Awaiting your reply.

Mark

 

[gidds]

Re: Help me so I dont ruin anything please (Prop Install)

Mark?..first of all?.Thank you for your complete reply. Rarely do I get a comprehensive answer to a question?..

With regard to the prop /trim tab issue??I talked to turning point and they stated that no matter the pitch, the rake of the performance props will still ?meet tab? with my Mercury 1350. I think I will go ahead and get one of the old performance tabs (saw one version on oldmercs) either the short one or the extended one.

With regard to the RPMS?..I seem to be putting the cart before the horse?I have had an on going issue that I am trying to resolve. It seems to be either carb related, link/sync related or switchbox related. I cannot seem to get over 3200RPM / 26MPH with the engine and old prop. I was hoping to see if changing the prop would make a diff. since I needed to replace it anyway.

I am not mechanically inclined but I think I am going to try to perform the Clams ?link and sync?. I along with the original owner rebuilt the carbs late last year and I feel that we rebuilt them to the previous measurements (floats, needles, etc) but we did not adjust. I also pulled the plugs that I put in early summer (see my pic in thread ( http://forums.iboats.com/showthread.php?t=225350 ).

I?m thinking I may try the link and sych or have someone do it locally. Then try the old prop and then probably replace the new 21 with a 19.

I really hope I can do the link and sync myself.

The Glastron V-166 does not have any steps. I purchased and installed an original Mercury tach this summer.

The ?pop rivets? are actually the vent holes. I looked at the picture and they do look like pop rivets but I think the camera flash is reflected. They are holes.

 

[45Auto]

Re: Help me so I dont ruin anything please (Prop Install)

Hi Gidds,

Mark is right on target, and I think you're right about putting the cart before the horse. Your prop pitch (19" - 21") is well within a reasonable range for your boat. You have some problem besides the prop if you're only getting 3200 RPM / 26 MPH. You need to get it running right then you can make an informed decision on changing prop pitch. Only way you'd gain the additional 3000 RPM or so you should be seeing from changing prop pitch would be if you just left it off and ran the bare shaft!

- Throttle opening fully?
- Choke open fully?
- No vacuum leaks?
- Timing correct?
- Compression good?
- Fuel flow good (clean filters, float height, etc)?
- All passages in the carb clear?
- Incorrect carb rebuild?

My past experiences with people rebuilding carbs is that more often than not the problem is in the rebuild. Was there a particular reason you rebuilt the carbs? How was the boat running before that?

Just looked at the previous thread with your link. How did the plugs look before the carb rebuild? You have something bad wrong there that you need to fix before you toast your motor.

 

[gidds]

Re: Help me so I dont ruin anything please (Prop Install)

The boat ran good at one time and I went out a couple of days fishing on it (prior to owning it).....I dont remember specifics (RPMS, etc.) as I didn't own it. The previous owner got a good deal on a bass boat and said he would sell me the boat, motor and trailer for an incredible price (really incredible, $800) under the condition he would repair the transom. I did not have the extra cash lying around so I would wait. He removed the motor and left it sitting on its side for a while......I now know that this is not the correct way to store an engine.

Took the boat out and it ran ok. I still agreed to purchase and did so. Did alot of cosmetic work....rebuit forward seats, replaced back2back seats, rewired elec. etc. and spent time and money on other things when I should have paid to correct the motor. During this time, the previous owner and I removed the carbs and rebuilt. I think we did a pretty good job rebuilding them especially since there we two sets of eyes involved. I had a mechanic look at it briefly while on vacation. He pointed out that the spark plug wires were arching to the motor so I replaced all of them. He adjusted the needles some, checked compression checked fuel lines for leaks, etc. Never really finished it with him as vacation came to an end. I have also replaced the fuel pumps.

I checked compression when I changed the plugs a week ago and got115,125,125,117,125,120.

How hard is the link and sync to do?......do I need to pull the carbs off first and check them (I now have a service manual)?......

 

[Frank Acampora]

Re: Help me so I dont ruin anything please (Prop Install)

Old Glastrons were a relatively light and relatively fast hull for an all-around pleasure boat. years ago I was test riding in a 16 tri-hull with a Merc 80 that went over 40 MPH. I think you will find that the 1350 will push it quite briskly once you resolve the running and rpm issues. You may find that the 19 prop is actually a little underpropped once the engine gets going but may be just right for skiing.

Now, just for a little apples to oranges comparison, A Chrysler 90 on my 15 foot Glastron turns a cupped 19 pitch prop at somewhere around 5000-5500 rpm and 42 MPH. A chrysler 140 on my 21 foot cuddy turns a cupped 19 pitch prop just about 5,000 at 38 mph. The same 140 on an 18 footer went 42 with a 19 pitch uncupped prop.

Your Merc 1350 may be a little more potent than my Chrysler 140 so on the 16 footer, the 21 pitch--even with the cup-- may not be out of the question.

But first the engine needs to run correctly. Re-propping when the rpm is down to 3200 will do nothing except make the problem worse.