Lost power

[Ringhede]

I have a Mercruiser 4.3L. (year 2002) The power is ok up to 4000 RPM but it will not go up to 4600-4800. The propp is the same as in other boats of same type and they goes up to 4600-4800 RPM<br /><br />Can it be timing or carb settings or something else?<br /><br />The top speed is nearly same with 2 persons in the boat as if we are 6 persons.<br /><br />Strange!<br /><br /><br />The engine has got regulary maintenance every year.<br /><br />/Roland

 

[Bondo]

Re: Lost power

Welcome Aboard Roland,......<br /><br />When was the Last Time this boat saw 4800rpms,..??..

 

[Ringhede]

Re: Lost power

It a fantastic forum.<br /><br />My boat has never reached that speed and high RPM:s<br />but there are other boats of same brands and same model and same engine and they goes much faster with same prop and engine. <br /><br />So I think there is something with my engine.<br />The power is realy good even with top weight in the boat but it never will go up in top RPM:s with nearly empty boat.<br /><br />The throttle opens full and I reach topp RPM when the drive isn't in gear.<br /><br />Normally it could be the wrong size of prop but the boat has the same size as other boats of same type.<br /><br />The speed is maximum 32 knots and other boats reach 40-42 knots with same engine and prop.<br /><br />The boat reach 32 knots even with 8 people in the boat, strange<br /><br />(in Sweden we use knots for speed, I think isn't same in US)<br /><br />The engine runs good and have a good sound but it lose power over 3900-4000 RPM:s <br /><br />Best regarads, Roland

 

[Bondo]

Re: Lost power

Normally it could be the wrong size of prop but the boat has the same size as other boats of same type.

THAT,..... Doesn't Matter.......Every Hull is Different,... Period.....<br /><br />I'm Guessing that your Tach is Wrong,.... Check it againest a Known Shop Tach........

 

[horsefly38425]

Re: Lost power

I would not bring rpm's that high with no load on the engine lots of bad stuff may happen like / kaboom

 

[Ringhede]

Re: Lost power

kaboom, why?<br /><br />If I speed up my cars engine to maximum rpm who it is allowed to run, noting strange happens.<br /><br />What is the difference with a boat engine?<br /><br />I have speed up my boats engine to 4800 rpm only a few seconds to see if the trottle works and so there isn't any stop in the wire system.<br />No kaboom.<br /><br />Back to bussines,<br />The speed of the boat is measured by a GPS instrument and is nearly same as the ordinary speed instrument.<br />But the speed is to low for this type of boat. <br /><br />I plan to check the timing this weekend to see if it is ok.<br />I know that it shall be 10* BTDC <br />But on what rpm:s? 650?<br /><br />If that is ok I will look at the carburator but it can be tricky to adjust, some guidlines?<br /><br /><br />Best Regards Roland

 

[Bondo]

Re: Lost power

Well Roland,..... It appears that you've Already got your Answers,.....<br /><br />But,....<br />What Other boats do is Totally Irrevelant to What Your boat Does.......What part of this statement Don't you Understand,.????<br /><br />There's Probably Nothing Wrong with Your Motor,.... Yet,... Although if you keep Free-Wheeling it to 4800rpms with No Load,... There Will Be.......<br />Same goes for your Car engine....<br /><br />And Besides,.... What an engine will Rev to Without a Load Just Doesn't Matter...... <br />Your 6 cylinder will Rev to 5000rpms if it was running on Only 4 cylinders,.. WithOut a Load......<br /><br />I Think you're Just Over Proped......... Drop Down 2",+ See..........

 

[Ringhede]

Re: Lost power

My boat is a Uttern S64 with a Mercruiser 4.3L with 190 hk.<br /><br />I don't compare this with outher boats of same size and different brands lika Baylinaer etc.<br />I compare this with outher Uttern S64 with same engine.<br /><br />The boats are produced by same productions tools and have same form and weight.<br />The differense is that normally this boat should do 39-41 knots. (depends of wind and how clean the bottom of the boat is)<br /><br />A god picture of the boat<br /> http://www.batnytt.com/bn_2002/bn12_02/samm1_bn12_02.html <br /><br />The size of the prop is sama as the original. If the prop would be to big I should miss power when the boat is full of people.<br /><br />The engine sounds good and it have a lot of power up to 3900-4000 rpm but then it ends.<br />Strange.<br /><br />Last weekend I changed the sprark plugs and now it is NGK BPR6EF. The old ones was 4 year old and the company who made the services had never changed them.<br /><br />I come back when I have checked the timing this weekend. <br />/Roland

 

[searay3]

Re: Lost power

This may be an obvious...but, do you trim the drive up after the boat planes off? (plowing the bow)?

 

[Ringhede]

Re: Lost power

Now I'm back.<br />This weekend I have checked the timing.<br />At 650 rpm it is litte to low 6-8* and should be 10* <br />If I increase the speed to 1000 rpm the timing is 10* and werry stable.<br /><br />Can this be the reason why I'm losing power in top speed? (It seams to be so little wrong)<br /><br />At the cower of carburator I read that it should be some special timing equipment. I have used a ordinary who can be used to cars etc.<br />Did I use a wrong type or?

 

[180shabah]

Re: Lost power

If you have Thinderbolt V ignition you have to put the system into base timing mode first. Otherwise you will be way off.

 

[boathog]

Re: Lost power

ground out pur/wht wire start eng then ck timing.

 

[KRS]

Re: Lost power

bottom fouling, heavy hull (water in wood/stringers/transom/floor), unbalanced prop, needs tune-up, bad gas, bad tach (like Bondo wrote), .... I'll think of more possible reasons later.

 

[whywhyzed]

Re: Lost power

Trade props with a faster Uttern.<br />Check compression on the engine. Look for vacuum leaks around the carb base or manifold in general.<br />Check and evaluate the spark plugs.<br />Set up the carb with a vacuum gauge.<br />Check for exhaust restrictions (flapper valve).