max rpm's on v6 center console

[jy118lfd]

Re: max rpm's on v6 center console

No, it seems to go faster but not at the pace you would expect for the throttle input. At about 4000 it cruises around 32 to 34 sounds great but then you open it up and it only goes to 42 44

 

[Dhadley]

Re: max rpm's on v6 center console

In a way thats good. It would seem the hull is in good shape then. Have you ever had a different motor on this boat or this motor on a different boat?

 

[jy118lfd]

Re: max rpm's on v6 center console

Yea a 235 when I first got it. It ran 62 mph at 5100 with a 22 pitch stainless prop before the motor coked up and tripped the number 6 ring. I was trying to set it up when that happened butit was better that it did cause the motor had corrosion issues and the crank and 4 rods were bad. Only the top main looked good so I changed the midsection and put this used 150 on it

 

[jy118lfd]

Re: max rpm's on v6 center console

Never ran this motor on a different boat

 

[Dhadley]

Re: max rpm's on v6 center console

Did the 235 ever get more than 5100 rpm?

 

[jy118lfd]

Re: max rpm's on v6 center console

No it lost number six before I changed the prop and rpm dropped to 4400

 

[Dhadley]

Re: max rpm's on v6 center console

Are you using an OMC tach set on position 6?

 

[jy118lfd]

Re: max rpm's on v6 center console

Yes and a tiny tach on the number one wire both read within 50 rpm of each other

 

[Dhadley]

Re: max rpm's on v6 center console

Excellent. Heres the deal -- and this is why there were so many questions eliminating other things -- in the 80's there were some flat back V6 crossflow blocks that got out that had this problem. I had one. No matter what you do it acts just like you describe. It runs excellent but you can never get the r's up where you want them. Or where you'd expect they'd go with the changes you've made. Oddly enough the motor I had came with the 1" carbs also.<br /><br />We did everything you've done plus we put that motor on a buddys boat and his motor on my boat. The issue followed the motor. <br /><br />We even took the motor apart and changed the porting to a 200 (it was also a 150/175 block). It helped some but not like it should. Now, heres what OMC engineering told me -- I'm just repeating what they told me. They said the front half is pourus and the incoming signal is weak. What that means is when the piston goes back its supposed to suck fuel/air in thru the reeds from the carbs. Because the front half of the block is pourus the carbs are not getting as strong a suction as they normally would. <br /><br />We ran that motor for a couple of years with no problem. As far as I know it never had any problems after I sold it. <br /><br />Its just a possibility but it sure sounds like thats whats going on.

 

[jy118lfd]

Re: max rpm's on v6 center console

The powerhead is from an 83 motor<br /><br /><br />So if I put the 1" carbs back on it and keep an eye on the carbon (decarb 50 hrs or so) It will live? I am not so worried about the speed but longevity Don't want to lose fishing time. <br /><br />I have another 150 block and am going to build that motor over the summer I was going to do it and change over the next winter but if I get it done sooner I will change and let you know the results.<br /><br /><br />Thanks for all your help I really can't thanks ENOUGH

 

[jy118lfd]

Re: max rpm's on v6 center console

One other thing I was thinking about. I was going to do a leakdown test I feel that if the motor is worn a little that the blowby would mix with the precharge and lower the primary compression and cause the same problem at rpm... Just a thought and an easy test I will let you know.

 

[Dhadley]

Re: max rpm's on v6 center console

Thats a good idea. Obviously we're always open to look at other things. Like I say, that may not be it but you sure mirrored what I went thru.<br /><br />We ended up with some 1 1/4" carbs but the 1" should sure be easy on fuel! I would say you have a good plan. Keep us posted.

 

[jy118lfd]

Re: max rpm's on v6 center console

There is a good set of 1990 150 carbs on E-bay Do you think they would be good? I think they are 1 1/4"

 

[Dhadley]

Re: max rpm's on v6 center console

I like the 1 1/4" carbs although there are several versions. They seem to have a good balance between low & high rpms. And we're talking recreational motors. If we were trying to get top rpm/speed out of a cf on a Hydrostream thats a different deal. <br /><br />I would think that if you could get those carbs at a good price, go for it. Cant hurt to have spare pieces for the motors you have.

 

[ondarvr]

Re: max rpm's on v6 center console

It seems we have very similar problems, boat size, type of motor, props and RPM. Is there something going around, BIRD FLU? I will keep you posted with my results.<br /><br />Good Luck <br /><br />post "200HP RPM&prop"

 

[jy118lfd]

Re: max rpm's on v6 center console

ondarvr I will let you know if I find out anything else but Dhadley seems to think I have the problem child, not to many around and it makes sense cause it will not respond to anything. I have a couple of checks to do but not much left to do I will keep you posted

 

[jy118lfd]

Re: max rpm's on v6 center console

Did a leakdown test yesterday about 18 to 22% so the rings are tired probably the problem. Compression is still at 80 to 85 on the motor believe it or not but the highest one is number 6 <br />I decarbed a couple or times and got some carbon out, pistons look fairly clean so I feel this is why I can't get the r's I need I am going to put together the other powerhead. <br /><br />Dhadly I need rods for the other 150 is there a difference over the years and v4 or v6 or can I use any rods.

 

[Dhadley]

Re: max rpm's on v6 center console

You can use any V6 or V4 crossflow rod from 1974 & up or a 60* rod. Same thing.

 

[jy118lfd]

Re: max rpm's on v6 center console

Thanks I will post when I get it on and going for now I am going to run the tired motor and put together the new one. I should have it ready in a couple of weeks as the block is bored and honed and ready to go. If I can get the time to work on it as the fishing really has turned on lately

 

[jy118lfd]

Re: max rpm's on v6 center console

Well I have 65 hrs on it now this season and just did a decarb although it really did not need one as the tops of the pistons and plugs look like new. I have run carbon free in the tank and it seems to work. No loss of power still runs 42 wot at 5100 with the viper 14 3/4 17 prop. I got hold of a 15 x15 alumnium and tried it 5200 rpm wot at 36 mph fully trimmed. So I feel the ring seal is the reason for the loss of power and rpm not overpropped or setup. I am going to try to raise the motor to the highest hole (one hole higher) as the viper does not lose bite like the alumnium 15x17. I will post with the progress. <br /><br />I hope this helps some of you out there