Why is my Hydrostream Valero YT with a 235 Johnson so slow??

[perfmarine1]

I think you will be fine with adpt and meg you have after running the # again. Different adpt"s will bolt up to different motors with only suttle changes, as long as they are for bubble back motors. First I would try raising up motor,or smaller prop and see what happens. That trophy will run good near the surface try jacking it up and see what happens. You realy need to be propshaft close to even with bottom,Low water pickup,over hub prop for it to run fast. Since it appears to be stock 235 and you have good spark,carbs done,compresson even but a little low, it should run. I remember a 20' Hydrostream vulture rigged by a dealer with a 235 ran just over 60mph,I jacked it up,added nosecone,and a Hoss 28 propeller and it ran 78mph. Nearly 20 mph gain. Give it a try you need to do it anyway!

[Fullthrottleguy]

I think you will be fine with adpt and meg you have after running the # again. Different adpt"s will bolt up to different motors with only suttle changes, as long as they are for bubble back motors. First I would try raising up motor,or smaller prop and see what happens. That trophy will run good near the surface try jacking it up and see what happens. You realy need to be propshaft close to even with bottom,Low water pickup,over hub prop for it to run fast. Since it appears to be stock 235 and you have good spark,carbs done,compresson even but a little low, it should run. I remember a 20' Hydrostream vulture rigged by a dealer with a 235 ran just over 60mph,I jacked it up,added nosecone,and a Hoss 28 propeller and it ran 78mph. Nearly 20 mph gain. Give it a try you need to do it anyway!

I agree that i'll need to put a nosecone on the lower unit and get a different prop to get some speed; but have a hard time believing that this motor when running well can't push this prop to redline on my boat. You'd think it'd launch like a rocket and then hit redline and be limited top speed wise by the lack of prop pitch. It barely gets out of the hole and onto plane with two people aboard, it would never get going with any more prop. I raised the motor two inches eariler this week and went for a run, with the anticavitation plate .5" above the water line while running full out the prop would cavitate and loose thrust/speed if i tried to raise the bow at all and air it out. I'd really like to determine if this motor is in need of a rebuild over the winter while the weather is still decent enough up here to test ideas out.

[perfmarine1]

Shoot us a picture of the back of the boat,with motor level and camera low so we can see bottom of boat. A 26 trophy plus is a very agressive prop and hard to plane,not sure why but I tried one on a Bullet bass boat with a 260 and it was hard to plane and did not run well. A 28 hoss planed it better. I thought the trophy with less pitch would jump it on plane,boy was I wrong. Toss on a 21-24 pitch and see what happens,then you will know.

[terry taylor]

I read the procedure to check the operation in my repair manual - looks good. Besides I think a missalignment would lead to a heasitation during acceleration but wouldn't affect WOT performance. On the hose it starts right up, idles without quitting and seems to rev up fine.

The more important thing is do all the butterflys open completely level horizontal when handle or foot pedal is floored thanks

[racer]

The head numbers posted are late 81 and compression with those is generally 110 psi so you are close. Sounds like you may have a set up issue. Have you checked to see how straight the bottom is and if it flexes under load?

[Fullthrottleguy]

Shoot us a picture of the back of the boat,with motor level and camera low so we can see bottom of boat. A 26 trophy plus is a very agressive prop and hard to plane,not sure why but I tried one on a Bullet bass boat with a 260 and it was hard to plane and did not run well. A 28 hoss planed it better. I thought the trophy with less pitch would jump it on plane,boy was I wrong. Toss on a 21-24 pitch and see what happens,then you will know.

This is a picture of how i've been recently running it; I've ran 1" higher and the prop slips pretty bad a full speed - RPM goes up and speed goes down. I also lost the ability to raise up the bow at speed - instead of lifting the front it would shoot a big rooster tail while at speed. 1" below the current location allowed me to raise up the bow at speed and air out the boat - although at 55 MPH i think im going too slow to really be up on the pad/sponsons. Top speed was basically the same with all 3 locations.

[Fullthrottleguy]

The head numbers posted are late 81 and compression with those is generally 110 psi so you are close. Sounds like you may have a set up issue. Have you checked to see how straight the bottom is and if it flexes under load?

I've heard of the poor build quality on some (most) of the earily YT hulls, this is an '86 so it falls into that category. I read that the weak spot it the pad its self and so went about jacking the boat up off the trailer with a 4x4" block of wood accross the width of the pad at about 18" from the back of the pad. I raised the back of the boat clear off the trailer with a hydraulic jack while observing the hull for deflection - it looked good. I haven't put a straight edge on it, but I will tonight and report as to what i find.

[JWTjr.]

Look for longitudinal cracks and crazes in the gel on the sides of the pad, along with any abnormal bulges, deflections, etc. Almost 100% of the YT hulls from early 1986 until early 1988 were not laid up correctly, so there is a void between the outer layer of glass and the balsa core. This will cause the conditions you're experiencing. In addition, the setup you are showing in the photos will not allow you to obtain speeds much over 60 even with a good hull. No torque tab on the skeg (and not much skeg left as well) is the easiest and cheapest fix. With no nosecone, that gearcase is ok up to about 84 mph...but that's if all else is OK with the setup...which it is not. The engine is crabbing through the water at a severe angle. There is excessive slip and ventilation leading to cavitation. The setback appears to be adequate, however.

John

[JWTjr.]

As for the engine, obtain a V6 test wheel and go to the ramp. If compression is over 100 and within 10% on all cylinders, it's fine. Spark is fine. Do a linkage and synchronization per the manual and ensure carb butterflies are opening all the way. Using the test wheel advance throttle to 5000+ rpm and set timing to 26 (30 is way too high and based on the fuel available in 1981). If the engine can pull the test wheel to 5000+ rpm on the ramp, the engine is fine.

John

[perfmarine1]

If that is the trophy plus prop is a old one. It looks to have very little cupping,that may be why it cavitates so bad. The newer trophy plus props are 4 blade,with lots of cupping and sm hub. I have one,a 24" on my 86 20' heavy procraft bass boat with a 150 and it bolts on plane,and I can jack it way higher than yours is and it still bites and hits nearly 60mph. That prop got to go.

[Gorilla0178]

How about a spun hub, not sure if its been mentioned.

[bigbluechevy454]

I still.think.u should try another prop.that's the easiest thing u.can try.what would.it hurt I'm sure some.one has know.you could borrow. I have a smilar problem and I was like u .thinking it had to be the motor and. Had a mechanic check.it .out and it turned out the.prop was worked and not true to what was stamped on it

[Fullthrottleguy]

Ok guys, there have been some excellent thoughts comming forth by all so lets recap where we're at after today.

JTWjr. (John) - I checked out the hull today after work... She seems pretty true, with a 3' straight edge I observed that most of the pad is perfectly flat; the worst hook i found was about 3/16" over a 3' span. It doesn't seem to move when i jack it up with a block of wood on the pad. There are some horizontal cracks on the vertical sections of first 3' of the pad; but I also see evidence that the floor (and maybe more) has been replaced at some point - so hopefully these are old. This was a good thing to check, but i think it would only explain a reduced top speed - not lazy out of the hole. The bottom end on the motor currently is from my '78 235 parts motor - i'll be swapping it out for the unit originally from the '90 175GT in the next week after my parts come in for the rebuild - it has a better skeg. Can you please explain why my motor would be "crabbing" and how i can stop it from doing so?

bigblue, JTWjr and perfmarine - I'm also in the process of looking for a test wheel to borrow locally - although can't see to find one; I talked to my local marina today and they are willing to lend me a lesser pitch prop that i can try out and see if the motor will pull upto redline. BTW i was mistaken, its a tempest plus not a trophy.

As it stands now the two most likely scenarios as i see it are: A) that either the prop has been reworked - substantially.
B) that the jets in the carb have been drilled and its getting too much gas (as perfmarine1) suggested the other day. The plugs do seem a bit more wet than im use to in other motors and it would explain the rough idle, but then smooth but slow accleration. I'm going to call the marina tomorrow and add a set of new jets to my current order of parts to rebuild my other lower unit.

I can feel the weather getting cooler up here in Ontario already; I'll be testing this thing into october with a snowsuit on if i have to!

Thanks again guys,
Dave.

[bigbluechevy454]

Good luck post the results

[JWTjr.]

a 3/16" hook over 3' is huge. It's power hooking. The core is bad.