Boat speed question?

[jordy1380]

Ok so I have already started a thread here: http://forums.iboats.com/boat-topic...fast-should-i-able-go-604522.html#post4211809

and I've been asked to start a thread on this forum sub thread.

I have a 88' mercury xr4 150 hp that may have some issues. I have already had problems with getting it started and i got it up to 30 mph which people are saying it should go faster than that, closer to the 55-60 mph range. I have a few pictures of a possible problem area which are in line with the fuel system. It's an oil injected engine as well if that information is needed. The serial number is 0B122909. In the pictures is where the oil line comes together with the fuel line and I think that this is a problem area. I was running the engine on idle with the ears attached for a few minutes and the vertical tube didn't ever fill with fuel. I think that may be something with the fuel pump?? I've also noticed that when it was running there were bubbles

 

[Don S]

Re: Boat speed question?

You missed posting some VERY important information in your post here.

WOT only 3000 rpm. That my friend is an engine problem.

 

[jordy1380]

Re: Boat speed question?

You missed posting some VERY important information in your post here.

WOT only 3000 rpm. That my friend is an engine problem.

Thanks don! Could that be caused by the engine running 'lean' on fuel??

 

[Don S]

Re: Boat speed question?

It could be anything. There are much better OB techs on this forum than me, but I would be first looking for spark on all cylinders and compression on all cylinders. Any standard compression tester will work.

 

[wired247]

Re: Boat speed question?

Check your spark. You should be pushing 6000 without trying.

 

[jordy1380]

Re: Boat speed question?

The guy that I bought it from had it serviced before I bought it and they're all new spark plugs. However that doesn't mean that all 6 pistons are firing though so I gotta check it out. Should I be worried at all about the fuel line that I have the arrow pointing to in the picture? Or could that be related to a poor spark/compression?

 

[carholme]

Re: Boat speed question?

That s/n comes up as:

MERCURY - (150XR2 H.P. (1986 ))
Serial No: 0B122909 Model No: 1150766

Gerry

 

[jordy1380]

Re: Boat speed question?

He also also told me that he had the upper unit rebuilt in '05 would that make a difference with the serial on the unit? Its got an XR4 blackmax cover on it so that threw me off apparently lol

Would there be another serial number on the engine? The Seloc book says that theres another one on the block, but that may be different since it was rebuilt?

 

[jordy1380]

Re: Boat speed question?

Another thing that I was reading in my Seloc manual is that you want to try to drain most of the fuel out of the engine before winterizing due to the amount of alcohol?? in the fuel. If the fuel remains in the engine while it's sitting then it can cause more parts to 'gum' up. I'm going to check out all of the filters but I haven't gotten around to checking spark and compression yet. I'll need to get myself the proper tools first ;p

 

[hl]

Re: Boat speed question?

I am not sure if you mentioned the rpm. If it is turning 5000-6000 rpm you could have a spurn prop hub. As far as the first start, I have the same motor, and I found that you should prim the carbs before you go to the ramp. After you have launched prime again. Before turning the motor over turn the key, push the key in to turn on the enricher for about 8 to 10 seconds and try starting. You might need to push the key in while engaging the starter.

 

[jordy1380]

Re: Boat speed question?

I am not sure if you mentioned the rpm. If it is turning 5000-6000 rpm you could have a spurn prop hub. As far as the first start, I have the same motor, and I found that you should prim the carbs before you go to the ramp. After you have launched prime again. Before turning the motor over turn the key, push the key in to turn on the enricher for about 8 to 10 seconds and try starting. You might need to push the key in while engaging the starter.

Well the rpm was around 3000 when I went out last and I may go out again this weekend to drive it around the lake. The above posts, guys are saying it should be in the 5000-6000 range...??

What do you mean by 'prime' the carbs?? Start it up before getting to the ramp? I am going to start it like you mentioned next time. I read something on here about the 8-10 count and then engage the throttle in neutral to get it going. I did buy around $80 worth of diagnostic tools as well so that I can start tinkering with the engine. Once I get my next big paycheck I'm going to buy the OEM manual to get a better picture of things to do. I have the Seloc manual but a lot of guys on here say the OEM manual is much better. I'm going to change the lower unit oil as well as grease the prop before I go out as well.

What's a good grease to use on the prop? Does that need to be marine grease as well and where can you get a decent size tub for a good price? I'd like to get a tub of it for greasing the prop and some for a large grease gun to lube up the moving parts on the engine.

Has anyone changed the water pump on one of these with any problems also?? I was watching a youtube video the other day and when the guy took the lower unit off there was a seal that came down with it. He said, "I'm going to have to take off the head unit to put that seal back on" which just scared me a bit even thinking about taking that apart. I watched some other videos and the lower unit came right off with no problems and it looked like it might take about an hour or so. Anyone have any major problems to be aware of when I change the water pump?

 

[jordy1380]

Re: Boat speed question?

Which water pump would be the one to use?? The serial # is 0B122909 does that count as "A904646 & UP" or in the XR4/Magnumm II category?

here is the link to the pumps: Mercury Water Pump Repair Kits - iboats

 

[Chris1956]

Re: Boat speed question?

What prop are you running? That 17 footer should get into the 40s with that motor, probably with a 19" pitch prop. It takes a whole lot more power to go faster, and some boats do not have hulls fast enough to get into the 50s.

I also suspect your tach is inaccurate, as 3000RPM does not usually produce 30MPH, unless on a low drag hull.
Let us know the results of the compression and spark tests.

 

[jordy1380]

Re: Boat speed question?

What prop are you running? That 17 footer should get into the 40s with that motor, probably with a 19" pitch prop. It takes a whole lot more power to go faster, and some boats do not have hulls fast enough to get into the 50s.

I also suspect your tach is inaccurate, as 3000RPM does not usually produce 30MPH, unless on a low drag hull.
Let us know the results of the compression and spark tests.

I'm not sure of the pitch on the prop but it's got 3 blades. I'll look on the prop when I go home later and post the pitch on here. I was thinking that could also be a problem if my tach is off. When I take it out again this week I'll post rpm's again. I need to post idle rpm's as well as rpm's at WOT.

 

[jordy1380]

Re: Boat speed question?

Prop is a 14.5 x 23 ballistic

 

[hl]

Re: Boat speed question?

When I mentioned prime the carbs, I meant to pump the primer bulb until you feel gas going to the carbs. After you have the boat in the water pump the primer bulb until it is hard. If you do not have a choke then you have an enricher. Turn the key to on without engaging the starter and push in on the key and hold for about 8 to ten seconds and then turn the key until the starter engages. Don't forget to pull the idle arm up about half way before starting. You almost have to flood these old mercs to get them to start. You probably have the carbs that are factory set(needing no adjustment),but have someone check them. You might try taking the plugs out and looking at the top of the pistons for color.

 

[wired247]

Re: Boat speed question?

Prop is a 14.5 x 23 ballistic

I dont know what your hull is like but if its a 17 footer I'm assuming its not a tug boat. With that prop on an XR4 on a half decent hull you should be 55-60 MP with that prop.

Spark and fuel.

 

[Chris1956]

Re: Boat speed question?

That 23P prop may be a bit too tall for his boat/motor combo. But I will bet the tach is inaccurate.....

 

[wired247]

Re: Boat speed question?

That 23P prop may be a bit too tall for his boat/motor combo. But I will bet the tach is inaccurate.....

If he's going 30 MPH at 3000 thats about right in line with how fast he should be going with a 23 pitch prop at 3000 RPM. Thats about what mine runs at 3000. I think he's got some plugged jets or half his plugs arent firing. Could be something weird like his timing not advancing too.

 

[Dukedog]

Re: Boat speed question?

I'd really be lookin' at tha stator also.......