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

[Fullthrottleguy]

What kind of tester? It needs to be set at 7/16" gap to simulate compression. It should be a nice strong spark also.

80/81 or so was right in there when they started having problems with the motors burning down because of the crappy gas. One fix was to add thicker head gaskets or maybe even change the heads. What part numbers are they?

I'm running stock '80 235 heads (325638 & 325639 what yours should be) and get right around 125psi with 26* timing, premium fuel only.

I set the tester to a 1/2" gap and all six had a good blue spark. I'm going to check the numbers on the head tomorrow morning; i'll let you know what i find. I know the head gaskets are stock thinkness as I took one head off to take a peak inside and then replaced that gasket with an OEM one; the compression reading was the same before and afterwards. Good thought tho.

[Fullthrottleguy]

I would never set timming any higher than 26 degrees @6,000 rpm on that motor. That being said have someone work the throttle back and forth to insure that the timming trigger is in fact moving to full advance. These systems tend to stick. If so it will require removeall of the flywheel for cleaning and lube. This will be a good time to check the flywheel key. They break and the flywheel may be out of place. This can be checked with a dial indicator for TDC on #1 cylinder and look at the timming pointer.

Ok thanks for the advice, I'm really impressed with the response everyone has given me trying to help me sort out this issue.
I'll put the timing back to where it was; that seems to be a consenses... detonation must be a big issue with these motors as everyone suggests less timing that stock (says 30 degrees right on the motor). I did a quick check of the flywheel location the other day before i put it in the water; i used a pen in the spark plug hole to find approximately TDC and saw that the timing needle was pretty close to 0 so im sure its ok. I too wondered if the flywheel location was off. I've checked the movement of the timing arm too - seems fine. Keep the good ideas comming guys - i really appreciate everyone's input.

[Fullthrottleguy]

Yes check those heads,this could be someone changed the heads to higher comp and then sold it with different heads and did not change the jets back to what they should be. I have run into this several times. you must check the jets and make sure they were not drilled,this will kill the power.You can not look at the size on the jets on a motor this old size must be checked,as too many were modded and all screwed up after sold. Too rich at idle will make it shake also,this is why I brought this up.Low compresson is your first red flag. Also pull off a by pass cover and check the porting,that will be your second red flag. Do a running DVA check on the ignition wires to coils first and make sure it is good. Good luck.

Checking that the jets wern't drilled out is a very cleaver thought - i know i tried that on a dirtbike when i was much younger and it never ran right again. I will pull the carbs back off tomorrow. Now that you mention it; the plugs all look a little more wet than im use to on other engines....so you never know.
When you say to check the porting under the bypass cover...what am i looking for? Just to see if anyone has been messing with it in the past?

[Fullthrottleguy]

I saw this rig in an ad, The jack plate and engine are bottomed on transom and will need to be raised at some point. Sometimes one can heat stick an engine and when it cools might seem to run fine . After removing heads evidence can show mild to severe damage, scuffing on cylinders fom piston expansion. It could also show compression loss. Does this block have bubble exhaust chamber? it should thanks.

Yeah I just got it a few weeks ago; it was/is anything but set up correctly. Not a single gauge was hooked up, the motor as you said was all the way down on the jack plate amongst other things. Funny enough after hooking up the water pressure gauge i raised the motor about 2" on the jack plate (doesn't have a lwp) and now the prop will cavitate at full speed (55 mph), it also has lost the ability to lift the bow and instead just throws a big spray. Keep in mind the prop shaft is still about 2-3" below the pad. I guess these props really arn't designed to break the surface...or be anywhere near it for that matter.
I had one head off and it all looked fine (and pretty fresh) to me. Yes this is a bubble back X-flow motor.

[bigbluechevy454]

Maybe you should try another prop maybe someone worked it and its not what it says it is

[terry taylor]

The plugged jet that was found in the carb. and the one cylinder head you removed were they on the same bank of cylinders ? If not remove the other head, you may find damage that carb. barrel feeds. I,d remove it regardless thanks.

[Fullthrottleguy]

I set the tester to a 1/2" gap and all six had a good blue spark. I'm going to check the numbers on the head tomorrow morning; i'll let you know what i find. I know the head gaskets are stock thinkness as I took one head off to take a peak inside and then replaced that gasket with an OEM one; the compression reading was the same before and afterwards. Good thought tho.

The numbers on the heads are 327124 and 327125; I looked them up on boats.net and they are listed as the part number for the heads for an '81 as are the numbers you provided. I have no idea why there are two different part #s.

[Fullthrottleguy]

Yes the plugged jet was on the side of the engine from which i removed the head. The thing is - the compression is so even between all the cylinders that i wouldn't expect to find anything wrong with one over the other. Something that I should perhaps add is that the powerhead is a '81 Johnny 235 while the mid and lower are from a '90 175 GT. Could this effect anything? Exhaust restrictions perhaps? I have a complete '84 235 'Rude that i picked up a few days after i got this boat incase i needed any parts - appears to be seized. Some things look different that this motor but if it was an exhaust restriction i could possible steal the parts from the other motor.

[perfmarine1]

Here is a block with stock 235 porting, this is a 85 block but will look same. Note you can see where factory used milling cutter to make double hole with dimple in the middle,any ported block dimple will be missing. Click on pic to inlarge.

[perfmarine1]

Yes the plugged jet was on the side of the engine from which i removed the head. The thing is - the compression is so even between all the cylinders that i wouldn't expect to find anything wrong with one over the other. Something that I should perhaps add is that the powerhead is a '81 Johnny 235 while the mid and lower are from a '90 175 GT. Could this effect anything? Exhaust restrictions perhaps? I have a complete '84 235 'Rude that i picked up a few days after i got this boat incase i needed any parts - appears to be seized. Some things look different that this motor but if it was an exhaust restriction i could possible steal the parts from the other motor.

Yes the megaphone will be different as will the adapter plate,according to the parts at www.shopevinrude.com the 84-235 should work fine, sounds like you got your work cut out for you.

[terry taylor]

Have we mentioned link and syc. with the airbox off ? Also how,s it run on the hose, does it respond lively when burping the throttle . And sound and feel as strong as it should?

[racer]

30 degrees is toooo much for todays fuel, if it has survived at that I would agree on checking the jets. Too much prop for the height you are running a cav plate 1/2 inch up is low for that type prop. I would not run the boat at speed with the air box off as it will be forcing air down the other cylinders, this is a procedure that works better and is safer on a test wheel or dyno. Post a head number/ carb number with jets and what the ports looked like when you had the head off and I am sure we can help.

[Fullthrottleguy]

The block # is: J235TLC1B
The Head #s are: 327124, 327125
The Carb #s are: 325524

The jets in all 3 carbs are: #29 and #62C in the fuel bowl and #30 up top.

I pulled the cover off and observed that the ports appear to be stock. The weird thing is there seems to have been some metal removed (dremel marks) at the bottom of cylinder #1. They appear to be a clearance for the piston skirt when it reaches BDC. I pulled the cover off the next cylinder down and it didn't have this done to it - weird. The piston and cylinders appear to be in good shape.

Should we be focusing on fuel and timing here guys or is the real problem at hand only 105 PSI of compression in each cylinder. Buy that i mean, if everything else was perfect would a compression number like that make this thing substantially under powered?

I've attached two photos of cylinder #1 with the piston at BDC. I notice that the intake ports are not fully revealed - is this normal? I removed the covers off my other 235 in the back yard, but its seized and none of the pistons are fully at BDC to confirm this.

[Fullthrottleguy]

Have we mentioned link and syc. with the airbox off ? Also how,s it run on the hose, does it respond lively when burping the throttle . And sound and feel as strong as it should?

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.

[Fullthrottleguy]

Yes the megaphone will be different as will the adapter plate,according to the parts at www.shopevinrude.com the 84-235 should work fine, sounds like you got your work cut out for you.

I just ran the numbers on the 'Rude 235 parts motor - its acutally a '78 not an '84 - my bad. Exhaust parts are identical tho. It appears the only difference in the exhaust on the '90 175 GT midsection is the exhaust adaptor plate listed as part #30 on http://www.boats.net/parts/search/BR...ION/parts.html

The 235's call for part # 0388813 where the 175 calls for #0395819. They call it the "Exhaust housing adaptor". I would hope that the different parts only bolt up to the correct powerhead and therefore mine would have the correct one on it - but who knows. I assume i have to pull the power head to check this out. They list the megaphone as being the same.