Engine wont reach operating Temp.

brandonmayberry

Boat is a Rinker 242 with a 350 Mercruiser Mag MPI. Its currently at the shop and they just called and said it is not getting to operating temperature. It has been running rich and lacking power significantly. Most noticeably it wont plane out unless i tab all the way down and shift weight (have my wife crawl) to the bow. I imagine its not getting warm and thus the computer is constantly causing it to run rich and lack on its power. Thermostat and gaskets are brand new. I have not checked the impeller. Water pump was replaced new last winter. Any ideas where to start?
Thanks!

MarkB

Are all cylinders firing? Check for codes?  Is the temperature sending unit broken - giving cold readings, but it's really hot, and it stays stuck in start up mode?

brandonmayberry

All cylinders are firing and there are no codes. Not sure about the temp sending unit. The shop said the gauge is working because they checked in but i know that last time i had it out and ran for 15 minutes it never registered at all, it just stayed buried to the left so it is staying extremely cold. If im not mistaken this boat has a temp sender for the gauge and a switch for the computer.

youstolemybeer

start it and feel the risers, if they are warm then the thermostat is working and you have a goofy gauge or ground. If they are cool then open the thermsotat . see it you have something jamming the stat open.

brandonmayberry

They do get somewhat warm if i remember but i can put my hand on them without it burning me.

brandonmayberry

apparently the Thermostat was installed improperly. boat is now warming properly in the tank. I will take it out this weekend with hopes it performs correctly and then time to winterize it and wait until spring.

brandonmayberry

Well took the boat out to run and it warms up and sounds great and runs great at top end but still does not want to plane. Have to use trim tabs all the way down, full throttle to get onto plane with a completely empty load, 1/4 tank gas, no septic and no water with only me and my wife.

MarkB

Hmm. How do your props look. Lots of under growth on boat?

Michael T

@Brandon, when you say it runs great at its top end, I assume you mean its RPMs are within the wide open throttle range at its top end?  What is your W.O.T. range - 4800-5200? If your engine is running in that rpm range, hopefully at about 5000 rpm then I'd look at a slipping prop (hub shot), hull growth, too much weight or weight not balanced or water in the bilge. Your trim tabs are up and you have trimmed your drive up until the boat has started to porpoise then you've tapped the trim down just until the porposing has stopped? I'm not going to jinx you by using the O (osmosis)word!

brandonmayberry

Thank you guys for the responses.
Props appear good to the eye, only a few tiny nicks. No growth on the bottom. Ive checked for slippage by hand and they feel good. At WOT it is running about 4800RPM at 46MPH with tabs all the way up and trimming the outdrive up until the porpoise starts and then going back down a little.
There is nothing on the boat to adjust the weight as its completely empty right now because im going to store it for the winter. The only thing that is extra weight that didnt come on the boat is two extra batteries and a subwoofer.
It seems to run fine when it gets onto plane, however it does not want to get on plane. Its a fairly small boat for a 300HP 350mag MPI. It should plane without having to use the tabs when the boat is empty, However with just me and my wife and nothing else on board if i dont use the tabs it will just dig the rear into the water and push water all the way across the lake. We have gone completely through the fuel system and replaced fuel pump and every injector has either been replaced or professionaly cleaned and flow tested. it has new plugs, wires, rotor, cap as well. Flame arrestor is clean. Throttle plates are opening all the way.
There is a very very slow leak in the engine bay somewhere and after being in the water for 30 minutes or so about a half gallon to a gallon of water will come out of the drain plug so i dont think there is enough water to cause an issue.
Im at a lost as to what to do.

MarkB

Wait so after you put tabs down and get it to plane it goes 46 mph? 

Have you recently changed the prop? If so what pitch did you go for? Could be you have a top with more top and and less bottom end to help you with planing.

Where are your batteries? That could make a big difference especially on a bow rider.

I wouldn't be to stressed though about needing to use the trim tabs to plane if my top end was 46 mph. 

brandonmayberry

I did not change the prop. It's a brave 3 outdrive with 24p props. I'd happily sacrifice some top end if it would plane better. I can't plane with 6 people unless I move half the people up front. I'd be ok using the tabs with a bunch of people but it won't plane without tabs and no people which to me indicates a problem.  Also It's a cruiser, not a bow rider also. The batteries are all group 24 batteries. Two are blue tops and two are Oreilly brand group 24dcm. I've thought about prop changes but didn't want to spend the money if it won't fix it. 

MarkB

OK, so what I figure is with 4 batteries and maybe placed towards the stern, could have impacted performance (I'm still suprised, but adding a couple of more batteries in the very back does add weight). The props might have been able to do it before the extra batteries were put on, but maybe not now.  Only way to really find out is to take the new batteries out temperarily and go for a spin. 

I have a 260EC fitted with a 350 MAG MPI and B3 drive.  My props are 21P. I plane pretty easy, but it definetly affects my top end which at 4800 RPM is probably around 38 mph.

Michael T

Brandon, are you really getting 46 mph? Is that reading  from your speedo or a gps? If you have a 242 running 4800rpm at 46 mph that's pretty awesome with a 350. Mind you I think that is in the lower end of your rpm band and might indicate over propping. I'd like to see a gps verified speed.

Dream_Inn

That does not surprise me for the 242.  I had a '99 240 Sundancer with an alpha drive and would get 45 on a really good day.

Michael T

Must have been a pretty good day DI :-). My friend had a 2001 Rinker 242 with a 5.0 liter. On a good day it would hit 36 mph. A 242 with a 350 mag doing a "true" 46 mph is really good, imo! General (loose) rule of thumb it takes at least 12HP  to get an extra 1 mph.....so that 242 doing 46 mph with a 350 mag is really haulin' it.

Dream_Inn

MT, that 240 packed for a 10 day trip and full tanks, still got over 40mph.  The 12hp rule would say I wouldn't have even made 30mph.  What's your 360 get now?  I know my 400 tops 40, but I can honestly say I've never held her open to see top speed.

Michael T

The 12 HP rule is a loose prediction of what it would take to gain 1 mph from your existing baseline hp/mph. So, if someone had 220hp that would do 40 mph and wanted to get to 50 mph they'd need another 120hp.

I have had the 360 do 49 mph but did not have the drives trimmed-up for that. I'm pretty sure it will do 50 with normal loads and trimmed right. Of course, heat and humidity are a huge determinant of HP.

I always ask anyone who is discussing modifications they think they need to make to their (props, skeg, bottom, etc)  based on their mph if it is gps verified because, imo,  there are very few speedos that I have found accurate.  Livorsi/Gaffrig was the best non-gps speedo I aver saw and now I think even they have gone to gps.

brandonmayberry

I'm fine with the top end and like I said would trade if for whole shot anyday. It's just embarrassing and annoying that it won't plane out with anyone on board. I also have not verified the speed by gps, just what the speedo says and on a perfectly calm day and really hauling I was able to get the boat to 51 a few months back, however it still would not plane out correctly without having to drop the tabs and even then taking a lot of time to get up. I guess I'm going to switch the "celery stick" first thing next spring and see how it does and then start with prop adjustments and see if that's better. I just want to be able to leave everyone (usually only me and 3 other people) and their gear in one spot and not have to move people around to get on plane to drive back across the lake. 

I have read read of people with a 270 and even larger running the same motor and they can plane with 10 people and a load using tabs. The way my boat is it took me shifting everyone to the front, full tabs and a lot of time to plane with me and 5 others this summer. With this load of people I was also only able to get to about 36mph top end. 

Robs_232

Brandon,

I don't know if this applies to your planning issue but the Bravo 3 drive on my '04 232 with 350 Mag has an elongated hole where the trim/tilt cylinders attach to the drive. There is a plastic spacer that can go in front of or behind the cylinders attaching bolt. I encountered a trim problem after taking my boat to a marine company to have it winterized a year ago. They removed the drive to grease and check things as part of their process. When they replaced the drive they put the spacer, which is in the drive and can be removed, behind the attaching bolt. My boat struggled to get on plane this past spring when trimmed down all the way. I researched what could be wrong and found out about this spacer. I changed spacer location and it was the difference for me. I also learned that a lot other boats require the spacer behind the cylinder attachment bolt.

What really got me focused on this was after having my boat winterized the drive hit my extended swim platform when lifted all the way up, which it had never done before the service. Changed spacer location and the drive did not hit swim platform and boat planed like it did before service.

This is something easy to check. Merc B3 service manual discusses this with some warnings about stern lift. Like you, I had other engine performance related issues that made things more complicated to diagnose.

Rob

Michael T

@Robs_232 Awesome catch Rob! Those spacers on the aft bolts of the trim tabs can make a huge difference in the ability to induce negative trim when accelerating and holding the nose down, if required. I found that out once when I had twin B llls and I noticed they were both at different levels when trimmed fully down and thought - whiskey, tango, foxtrot ? Turned-out the spacers had been installed on the front of the pin on one and the back of the pin on the other. @Brandon - you should check that as it could make a difference!

frenchship

Here is the position of the spacer on my Bravo 111

brandonmayberry

Thanks guys, that is what i was thinking may help it out. I had switched it around once but the engine was running rough at the time so i wasnt able to notice. I switched it back to the position the manual shows and havent put it back like Robs and Frenchship with the engine running properly. The Bravo 3 manual shows it where the bolt is in front (the opposite of what you are running) however ive read about people switching them around. First thing this spring im going to do that and then if its still no good ill look into changing out the props. It just sucks that the boat is already winterized and i cant change it and run it so itll be a long winter of waiting and wondering. 
Thanks again so much and ill try to update everyone in the spring.

brandonmayberry

Well spring is upon us. Thought i would update. I went with a set of 20 pitch 4 blade props and it got out of the water with not problem at all. Now it seems to be running too high of an RPM at cruising. I was able to cruise at 36mph and 4600RPM. I only got to run it for a short while before weather was coming in. Going back out this weekend to see what it does down towards 3600RPMs. I think im going to send the 20p back and go with 22p. (i also changed the trim spacer)

Michael T

Mine were spaced to allow more negative trim.

I like more negative trim, as I find most cruisers ride bow (nose) up anyway so I need less adjustment of trim "up" than I will need "down" so I always place the shims where they will allow the most travel In (-ve trim) or "down" of the drive(s).