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Older 1978 r200 rides bow high


white2gawd1995
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o as the title states I have a 1978 r200 I have a yamaha f150 on the back I just rebuilt the transom because previous owner had transom height 23 1/2 weird I know.. its now 25 for my engine this thing rides super bow high and will porpoise with even the slightest amount of trim. I also have wedges anyone else with one these older hulls have any feedback on the ride their boat gives them? Batteries are also under the console and passengers up front make no difference this thing just rides bow high

20211103_161032.jpg

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Hi White2Gawd1995 -

Not sure how I missed this post yesterday.

Based on your photo and assuming the motor is trimmed level, it is too deep.  Bottom of cavitation plate needs to be at least 1 to 1 1/2" above the bottom of the boat.  When the motor is too deep, handling is terrible due to excess drag.  I believe your porpoising issue / bow high attitude will go away once the motor is raised.

You are already ahead of the game having relocated the batteries to the console.  

Did you install the transom wedges?  What was the reason for installing them?  

What is max speed and wide open rpm you are getting with that Solas 4 blade prop?  Ideally, it should turn up around 5800-6000 rpms, but that low I don't think you are getting in that range unless the boat is under-propped.  Also, a 4 blade prop should provide a little transom lift due to the larger surface area of the blades in the water at any given time and cause the bow to ride a little lower than a comparable 3 blade prop.  Do you have a 3 blade prop available to try?  Honestly, no need to start testing different props until the engine is raised.

One other thing to check.  Place a straight edge against the bottom of the hull and see if it is flat or has a rocker in the bottom.  It should be flat.  Rocker will  make the hull prone to porpoising.  If it has a hook in the bottom (you will see a gap between the straight edge and the hull), the boat would tend to ride with the bow low and require more trim to get it riding at an optimal angle.

We will get this figured out...may take a couple of tries, though.

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Thank you yea it seems to have a bit of rocker.. I have never seen another one of these hulls in person so I didn't know if it was by design or not.. I would have expected a hook considering the trailer it used to sit on was to short and about a foot and half used to hang off the back. I'm am turning pretty close to 6k and I think 38? Last I checked thats  a 15p blade.. I installed the wedges after I ran it a few times after rebuilding the transom thinking maybe I needed a lil more trim in.. I can only go up 1 more hole due to where I drilled it because the engine would be hanging really high above the transom cap

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So it seems I need to either add a jackplate or build up the transom a lil taller then that's a bummer I was under the assumption a 25 in leg should have a 25 inch transom but looking at where it sits if go higher it will put the top bolts very close to the top..I will add a better picture tommorow but this is what I have from when I first hung the engine not sure if you can see what I mean by how close it is to the top of the transom

98186752_3087258067999644_2038762057049833472_n.jpg

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Remember that in 1978, standard shaft length was 20" and 25" was considered a long shaft. 

Something else that comes into play is back then a 150 hp 2 stroke weighed around 385 and a comparable 4 stroke is in the 475 range.  These smaller boats are more sensitive to that weight change as to how it effects the center of gravity. A combination of the weight and increased drag of the lower unit will shift that center back further, resulting in that bow high attitude.  If you go with a jackplate, that is going to move the motor behind the transom more, impacting that center of gravity.  See what is available with the least amount of setback, should you decide to go that route.

If you go with the jackplate, be thinking about a set of trim tabs.  Tabs can overcome a lot of little gotchas and help control the bow better than relying on just engine trim.  I have a set of Bennett M80's on my 2160, and they are great for changing water conditions plus being able to drop them down to get on plane quick when I have a load in the boat.  My thought is it is more efficient to re-direct the water flow coming off the boat instead of relying just on prop thrust that is now pushing the transom up in addition to forward when trying to get it running right.

I am glad to hear rpms are close to 6,000 as that means the motor is not being over-strained due to improper prop size.  But, once you get the motor height issue resolved, a different prop with more pitch will be needed.  I also think you will see an increase in speed to the 40-42 range and much better fuel burn in the 3800-4200 rpm range.

Here is a picture of my boat with the engine at the proper height while running.  The top of the cavitation plate should be above the water line when on plane.

 

cavitation plate.jpg

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I see the model is a 2005 Yamaha F150TXRD, which is a 25 inch shaft.  Shaft length is measured from the top of the transom bracket to the cavitation plate:

image.png

Something does not look right based on your measurement of transom height versus where the motor is sitting on the transom now.  Can you measure it per the above example and let me know what you get.  It looks like you have what appears to be a 25" motor with a 5" extension bolted between the lower unit and midsection, resulting in a 30" motor.  I thought the motor looked a little strange yesterday, but since I have always been an OMC person, was not sure it that was normal for your motor.

Fix may be as simple as dropping the lower unit, removing the extension adaptor, extension for shift rod, drive shaft, and water line, then re-install the lower unit.  Motor will sit so much better on the transom.  The only possible issue is you may need to re-drill the holes, but that is much better than re-working the transom.

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So it actually ends up being 26inches I don't know why it would be 26 instead of 25 but that would explain my being 1 inch orso to low.. trouble now is I looked into pulling the spacer before I built up the transom due to it being a super weird height and seems it would need new drive shaft shift rod and tube non of them use adapter.. so i guess its do I wanna spend the money to build up the transom 2 inches or just spend the money getting rid of the spacer  what a bummer to have to mess with the transom again

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I would probably fix the motor first.  Was looking at Crowley Marine parts diagram and that motor only has a 20 and 25" shift shaft is $304.  25" drive shaft is $289.  Could not find any information on the water tube.

As long as the lower unit bolts are not siezed, dropping the lower unit is not that hard.  On OMC engines, hardest part was removing the shift rod from the control lever under the powerhead.  I am guessing Yamaha uses the same concept on the shift rod, but recommend you consult the repair manual for your particular model.  Drop the lower unit and confirm if this is really set up with a 30" lower unit or a 25" with the extensions.  Since the Crowley diagram only shows 20 and 25" shift and drive shafts, I think you will find yours has the extensions and should be removable since the 150 was never sold as a 30" motor.

One other option would be to find someone selling a used 150 lower unit with 25" shaft.

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Yea I think your prob right i may just pull the exstension i did look and found a driveshaft for 20inch case for like 200 bucks the shift rod ide prob just cut and tig it so I don't have to pull the powerhead.. would be much easier to notch the transom if it ends up to high compared to building it up anyways.. as far as it being a 30inch it doesn't seem to be the case every one of these engines I've seen or worked on all had the exstension so I'm pretty sure thats how they get 25 out of them and standard 20 is no exstension. I've had the lower of to replace the pump and all the seals and never saw a adapter on the drive shaft 

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I must say tho I thank you for your experience and taking the time to talk to me I will be doing this asap as I have not been able to properly enjoy after rebuilding and powering it..I will keep updated on the progress and outcome I just hope when this is done that it performs correctly haha if nothing else I will be saving prob 50lbs taking exstension and wedges off the back

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I feel very confident that once the engine height is set where the cavitation plate is 1 - 1 1/2" above the bottom of the hull, you will be pleasantly surprised.  

Also, helping others out is what we are here for!

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It is amazing how many people have a difficult time understanding that the cavitation plate needs to be above the bottom of the hull.  They think if a dealership set it at a certain height, that has to be correct.  I had one person that it took 2 years before he finally agreed to listen to me and raise his motor 2 1/2".  He sheepishly agreed afterward that it was a night and day difference how the boat handled much better.  You are already way ahead of a lot of people since you understand the concept of water rising behind the boat.  It gets more "fun" on a boat with a bracket...then you raise the motor 1 1/2" for every 1 ft setback.  Most brackets are 30", so the motor should be mounted 3 3/4" above the bottom.  The picture above is with a 30" bracket on my boat.

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Just saw this and I can attest that going from a 150 hp OMC 2 stroke to a 4 stroke Suzuki 150 hp and they are 2 totally different rides. I bow high and porpoise 🐬 now too . I bought a set of Bennett fixed trim tabs and it helped a lot out of the hole mostly but also stopped most porpoising and bow drops much quicker.  I will go back and check my transom and see where I’m at as the dealer had to mount the motor for warranty reasons. I changed the inside liner at the stern to rig it differently and due to it I had to make holes in the deck above where the bolts go . I did the stern to make the rigging neater as well as raise the scuppers due to the weight of the 4 stroke. I’ll look at mine this weekend measure again but I already know it’s not quite perfect and will change it ip during the winter.  I’ll try to post some pic just lost photobucket account so have to resize them.

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I also raised my suppers when I raised the transom I didn't like the old setup it was sort of like a box back there and the scuppers were above the bottom so it would always have about 2 inches of water what a odd setup.. well I had a merc 115 4stroke on here before I traded for the yamaha 150 4stroke and it pretty well rode the same thats why I was sure if the hull just kinda rode that way as it has a real deep keel that seems tobe a few inches lowered then the stern. I figured maybe it was trying to ride on that?

97642675_3082847111774073_316798479970074624_n.jpg

Edited by white2gawd1995
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I do also have trim tabs but I was trying to leave that as a last option im not fond of drilling into my new transom I even made a fiberglass block and glued it to my transom for the transponder.. if I have put tabs on the boat I will prob do the same thing. But for now I ordered a 20inch shaft that will be here Monday in going to pull the 5inch spacer and convert it drop the engine as low on the transom as it will go and see how that does

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Good idea on modifying the scuppers.  Anything to help get that water out of the wet well is great, especially when it helps reduce the amount of water around the bilge access.  I also like your idea of the fiberglass block for the transducer.

Once you get the motor right, tabs will not be a necessity, but they are a nice addition.  Once you are comfortable using tabs to adjust for both water conditions and weight conditions in the boat, you will wonder why you did not install them sooner.

Do you remember if the 115 sat as deep as the 150?  If so, too much lower unit in the water makes boats handle in strange ways.

You are talking about a 20" shaft, but I am confused.  If the motor with the 5" extension is a 30" motor, I would have thought a 25" shaft would be used if there is no extension on the current 25" shaft.  When you measured the current set-up, was it from the bottom of the motor bracket to the cavitation plate directly over the prop?  That measurement should be 30".

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yea the 115 had a exstension as well and sat very deep because the transom was a odd 23 1/2 it was so low it would spray up the cowling so when i traded for the 150 i rebuilt  the transom  being its was a little soft and raised it up..  and yes the measurements were from the motor bracket to the cavitation plate and like i  said it was 26 not 25... i dont think 30 is a option for the 150 i just think they got a 25 by adding the exstension

Edited by white2gawd1995
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So just a heads up I'm still in the process of trying to convert it to a 20 I've spent a few days trying to get my bearing carrier out with very little luck I got it to move maybe a 1/4 inch so far and then she stopped so im waiting on a slide hammer adapter to come in that I can hook up to my prop shaft I don't know what else to do at this point just yet..

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Have you tried something like this?

 

I made something similar for my Evinrude except I had a round metal plate that sat on top of the prop nut.  Run prop nut down flush on shaft, put hooks on carrier bearing and snug those bolts, then slowly back off the prop nut.  Repeat lowering the prop nut back flush, tightening hooks, then back off prop nut until it pops out.

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