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Compression question. 1983 235

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KyBullet

Member
I have a 1983 235 has low compression on 2 cylinders 4 have 88-90 other 2 have 30 and 50. I can spray pb blaster in cylinder wall and will bump up compression a little but will go back down. Could it be a stuck ring? Boat still runs just sluggish out of the hole, and feel loss of power. Will appreciate any help. thanks
 
You have broken piston rings or blown head gasket.-----Mechanik in a can won't help here.-----Pull heads off for inspection.
 
Agreed, and do not run it again until you diagnose and repair the problem, which will rapidly get worse if you run it. Quite possibly to the point of complete destruction.
 
I used to run a pair of those 235 HP motors ( 1982 models ) some years ago.-----Take the heads off is your next step.
 
From what im getting 90psi is what it should have, has the bubble back exhaust and is a low compression motor. Head has been off new head gasket. Piston looks good cylinder walls dont seem to be scorned.
 
Low compression values ( 30 and 50 PSI ) that were posted by you can only be due to broken rings or blown head gasket !!----If I saw 90 PSI on one of mine the head would be off in a heart beat.
 
I has to come completely apart to replace rings. If 30 psi is a correct reading, that is the same as no compression, to my way of thinking. Something is busted.
 
Your are confusing 235 HP motors. The 2.4L(149ci) 235 was a low compression motor the 2.6 never was... Numbers should be around 115-125psi
 
Carburetor throat size.----You say it has the bubble back exhaust.---That was only used on your style 235 HP model V-6 and later GT 175 ( prop rated ) HP models.----Early 235 HP had the 3.500" bore and later ( 1980 and newer ) ones were 3.625" bore.----GT 175 was the 3.625 bore.
 
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I do not see the ---" low compression " ----Cylinder heads / head gaskets offered for your motor.------I would be aghast if I saw 90 PSI on my motors.----Low compression kits / cylinder heads may have been offered at one time , hard to say.-----Why not remove the heads to have a look at the 30 / 50 PSI cylinders ???----No need to be scared to do that.-----Head gaskets are cheap I say !!
 
I have had head off that side cylinder walls looked good. And i put new head gasket on and head gasket brought it up a tad bit but not much. I appreciate all the great advice. Before this they all had 88-90 psi and boat ran great would push my 20xrd bullet well into the 80s. Thats why i was guessing it was a low compression motor.
 
Time to pull it down and rebuild it..the 2.6 motors have thin sleeves and wear is more accelerated on these. While it down do the 7 pages of block work to it and pick up a few ponys...
 
any extra information on the ( low) compretion engine or were i can find it ...........i bought a 1985 trophy with a ( 235hp evenroude V6 ) ( 18E235txcor ) on the back ..i forgot my compretion tester when i looked at the boat .guy was pretty honest when he said the compretion was between 90 and 95 on all 6 cylinders .thats a little low for my liking but i took her out for a ride anyway . from a dead cold she started right away idled well and ran good with lots a power ..got that thing up to 40 mph before she started to what seemed to be starving for fuel ....it was good buy and went threw out the summmer with no problems except keeping gas in the tank .no wonder they call it a two thirsty five .lol...........anyway .ive never heard of a low compretion engine could this be one of them or am i just lucky that this runs so well with the lower compretion ..any information would be greatly appreciated...thanks in advance .....joe
 
Yours is a big bore 2.6L and did not come with low compression options. 90-95 psi is low in my book for these but yours being a long shaft increases backpressure..might help a tad.
 
thanks for the reply ....im kinda disapointed as i thought it was a low compression 235 ..now i wont be able to trust it ,,fingers crossed ..one more quick question .......this boat also has a electric fuel pump attatched to the gas tank and the same hose runs up to the primer bulb ..does it realy need it or is the vacum from the primer bulb enough ..thanks again.
 
Fact-----There should be 2 fuel pumps near the starter motor if it is the original powerhead.----And those pumps work with crankcase PRESSURE and not so much on vacuum.-----These pumps are elegantly simple and reliable.-----No idea why someone would resort to an electric pump.----The primer bulb is nothing but a manual pump and it does nothing when motor is running !----Trouble shooting skills are severely lacking I say.
 
If crankcase pressure is low(worn cylinders) it will not drive the fuel pump/s enough at low RPM to supply fuel to carbs, some people install a electric pump to compensate for this..
 
+++ on the post above.----Some can not accept there is a basic problem and will try a ---" work around "----To try and keep a motor running.
 
guys ..( faztbullet / racerone ) and any one eles .i vary much appreiate your replys and input and truly beleive peaple on sites like this want to help and be productive .....true ..my trouble shooting skills arent that great..im a pretty good nuts and bolts guy when it comes to engines .thing is... im not that good with boat motors simply becouse ive never realy worked on them other than change plugs and points ....for me ....this is different ...this is a older 235hp that runs well but a few things bug me like the lower compression and the cyl type electric fuel pump attached 6 inches away from the 100 gal fuel tank with the primer bulb 2 feet away from the motor ....so yes ...was that pump installed at the factory or was it a work around becouse the engine starves fuel at wot .and it was just left in line even if it never fixed the problem .....a big motor like this is not cheap and to buy another older one would be like marrying my wife again .lol....my thinking is ..if i can get some input and advice from peaple like yourselves i could save myself from buying anouther motor ......work arounds are ment to get you back to shore not to be permanent .should i pull and toss the electric pump or leave it ??..once again thanks in advance .joe
 
Are there 2 pumps on your motor near the starter ???----I would install the factory pumps and then test run.-----But a very simple inspection of pistons / rings can be done.-----Remove bypass covers.-----Three of them on each side of the block ( 6 wee bolts each) , might cost you for 6 gaskets $2.00 each,----And you will gain $100 in knowledge.
 
thanks again for the reply....so what your saying is . .((.the only fuel pumps that should be there is the two on the motor ,the one by the fuel tank is a after thought ? )). .im located in ontario canada and the boat is being stored shrink wrapped for winter...its so far back in the storage area i cant get to it until spring even to look at the engine becouse its also coverd ....im taking the winter to do my research so in spring ill be ready ..3 things on my to do list is { 1] head gaskets ( easy) (2) primer solenoid . cracked caseing....(3) factory fuel pumps (.your sugestion ) i dont mind to drop a few hundred on it if i can save it as it will still be lot cheaper than thousands on a new motor ..after all ....isnt that the reason we spend our spare time tinkering .....
 
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