Boat has lost top speed and RPM's, Help

[Robertpel9]

I have a 1995 Chris Craft 19' bowrider with a 4.3 GS Volvo. They way i have had it propper for the last two years with my wife and i in the boat it runs WOT at ~4400 RPM and 47-50 MPH

For thelast week WOt is rght at 4000-4100 RMP andno more than 40 mph. when i put it in Nuetral and rev the engine up to 4800 it runs perfect, no misfired, nothing justsmooth as silk

What could be causing this. i keep it wetslipped but i jup in and clean the hull each week. Last summe ri lost a few mph down to about 45 mph due to buildup on thehull i cannot reach but it still would turn 4400-4500 rpm.

I am a little perplexed here, what cause s loss of rpm and speed?? Could it be marina Gas, I usually bring my wn down to the dock but we have had a lot of company and i filled it at the amrina with 93 octane. i would think that would be fine. I am a bit perplexed as it runs smooth as silk, planes instantly etc, i am just losing top end speed and RPM

 

[ne7800]

Re: Boat has lost top speed and RPM's, Help

is it possibale the flotation foam has soaked up some water?

 

[jay_merrill]

Re: Boat has lost top speed and RPM's, Help

I agree that soaked foam/water in the bilge could be your problem. You may also have some sort of an engine problem. The first thing that I would do is to place a large wooden block under the trailer jack the next time you come home from a trip. Jack the tongue up on the trailer as high as it will go, so that there is a good amount of tilt towards the stern. If the drain plug is not out by that time, pull it and leave the boat like that for a week or so. Between regular drainage and evaporation, you might get rid of alot of water.

BTW, don't rev your engine up in neutral. First, doing so is a good way to blow it up, because motors that have no resistence against the prop sometimes run away and blow through the redline in a hearbeat. Second, doing so isn't telling you anything anyway. Once again, there is no resistance against the prop and therefore, no load on the engine. You could have a couple of cylinders not firing and you'd never know it.

 

[Robertpel9]

Re: Boat has lost top speed and RPM's, Help

I won't rev it again in neutral, i was carful to keep it in the rev range but still i see what you are saying

boat is covered at all times and bilge is dry so i dont see how i took on water weight. It never sits uncovered and the bilge is always empty

Could it be that it was 90 degress and humid?? maybe i am paranoid but to be honest the engine sounded louder with a deeper growl at wot under load than usual and i trimmed the engine out and could still not get it over 4100 rpm

itran great otherwise i drive about 20 miles on the lake today at 3000 rpm and it cruised along fine, if i had not punched it on the way in i would have never noticed

Also all plugs were changed at the end of season last year and with a waxed hull this spring it ran 52 mph

Could this all just be algae buildup in the very bottof of the hull where i cannot reach to clean. I was thinking maybe but i did the same routine last year and did not have this issue

what gives??

 

[Silvertip]

Re: Boat has lost top speed and RPM's, Help

Bad gas, water in fuel, throttle not opening fully, weak fuel pump, restricted fuel line, -- just a few things to check.

 

[Jdeagro]

Re: Boat has lost top speed and RPM's, Help

Have you added anything to the boat, inside or outside?

 

[MikDee]

Re: Boat has lost top speed and RPM's, Help

Do you have a points distributor, or electronic? If it's points, check their setting, they maybe worn,,, Or, your centrifugal advance mechanism in the distributor, maybe corroded, & sticking.

 

[Robertpel9]

Re: Boat has lost top speed and RPM's, Help

Sounds like a lot of items to check.

I have a traditional distributor cap. I am not sure how to check the points but will find out. I do not have the tools to check fuel pressure, etc but will definitely have someone look at it as it sounds like i have a legitimate problem (My first in 2 years of use so i guess i can't complain).

I ahve company coming in tomorrow - is it safe to use the boat for the weekend for just cruising at 3000 RPM (it runs fine there anyway) or do i risk more damage or getting stranded, etc??

 

[IVAZ]

Re: Boat has lost top speed and RPM's, Help

It?s never good to run something when it?s not working properly. If it?s bad gas or a lean condition it could cause harm to the engine. If it?s possibly just the throttle not opening all the way, it will be fine. I can?t tell you either way.

 

[IVAZ]

Re: Boat has lost top speed and RPM's, Help

BTW, your distributer does not have points. MikDee had a rare oversight.

 

[nlain]

Re: Boat has lost top speed and RPM's, Help

One more thing, are you sure the trim is working.

 

[Robertpel9]

Re: Boat has lost top speed and RPM's, Help

Trim is working perfect

there is a shop near me that seels everything from 4k runabouts to 700k Pinafarinia designed rockship going for 400k. i talked to their lead tech today and he is going to come to my dock (i live about 5 miles from here) and replace the cap and coil and the fuel pump / water separator. He said he will give it a solid lookover as well but these items after 14 years must be replaced anyway and he is 80% sure it will fix the issue. He does not understand why i do not hear feel the engine bogging down or stumbling but said it is either not firing on all cylinders or is starving for fuel

Does that maek sense to you all

 

[nlain]

Re: Boat has lost top speed and RPM's, Help

Yes, especially if all of those items are 14 years old.

 

[witenite0560]

Re: Boat has lost top speed and RPM's, Help

I know this may seem obvious. But, it never hurts to ask, have you checked your prop to make sure there's not a rope, fishing line, weeds or such wrapped around it?