Cant get over 3200 RPM

[Waterproof]

I have a 19' ski boat that the previous owner put a "new" 350 in, what compression should I have, I am worried that he put some car rebuild in instead of marine and perhaps my compression is not high enough. I've played with the timing some with no positive results and the motor has a small 2 bbl. rochester dual jet on it. Thanks for the input here.

 

[vipzach]

Re: Cant get over 3200 RPM

140 would be a good compression reading, it could be a little lower or higher. I think you want no more than 10% difference between the cylinders. <br /><br />Did you mean to miss spell Texas?

 

[marunr]

Re: Cant get over 3200 RPM

tejas = spanish for texas

 

[Waterproof]

Re: Cant get over 3200 RPM

Would a compression reading of 140 indicate that high compression "marine" pistons were used in the rebuild?

 

[vipzach]

Re: Cant get over 3200 RPM

Originally posted by marunr:<br /> tejas = spanish for texas

Well thanks for the spanish lesson today! <br /><br />140 reading would be fine, I don't think pistons are one of the things that are really "marine" specific.

 

[Waterproof]

Re: Cant get over 3200 RPM

Update! Compression of 155-160 an all cylinders but one..... 125 on one cylinder, I noticed a "ticking" "ch-ch-ch-ch" sound that seemed to be coming from the exhaust on the same side of the engine as the low compression cylinder, is it safe to say I've got a burned exhaust valve on that cylinder? and would the lower compression on that one cylinder cause my WOT RPM to drop down from 4500 +/- RPM the engine should be turning to 3000-3500 RPM?<br />Thanks for the help.

 

[Waterproof]

Re: Cant get over 3200 RPM

Update! Compression of 155-160 an all cylinders but one..... 125 on one cylinder, I noticed a "ticking" "ch-ch-ch-ch" sound that seemed to be coming from the exhaust on the same side of the engine as the low compression cylinder, is it safe to say I've got a burned exhaust valve on that cylinder? and would the lower compression on that one cylinder cause my WOT RPM to drop down from 4500 +/- RPM the engine should be turning to 3000-3500 RPM?<br />Thanks for the help.

 

[rbezdon]

Re: Cant get over 3200 RPM

the answer is yes, the bad cylinder would drop your rpm as shown. I would more likely guess a head gasket though. You could dothe leak down test to try to diagnose better. If it a valve as you suspect, there is an outside chance it can be repaired without pulling off the head but I would pull it any way and get the head throughly checked out.

 

[Waterproof]

Re: Cant get over 3200 RPM

Thanks for all the help, I have some great news, after pulling the valve cover I located a broken exhaust valve spring on the bad cylinder. Seems a little time and a $3.00 part will have me up over 4000 RPM! for good measure I will replace all the valve springs with some heavier ones, and be out only $50. Thanks again for the replys!